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CLEAN ENERGY REVIEWS. Solar and electric inverter

CLEAN ENERGY REVIEWS. Solar and electric inverter

    What Are The Different Types of Solar Inverters?

    When deciding to go solar, choosing the right equipment for the job is crucial. The most important piece of solar equipment are the solar panels, as these will be producing your power. However, the next more important piece of equipment is the solar inverter. Not many homeowners know about solar inverters or what their role is in a solar panel system. What are solar inverters? How do they work? What are the different types of solar inverters?

    Let’s break it down for you.

    In This Article:

    What Are Solar Inverters?

    What many homeowners don’t know is that solar panels produce a form of electricity that most homes cannot use. This electricity is direct current (DC) electricity. The form of electricity almost all homes use is alternating current (AC) electricity.

    But how does DC electricity produced by solar panels get converted into AC electricity?

    This is where solar inverters come into play.

    Solar Inverters have the task of turning all the electricity produced by solar panels into usable power. It does this by converting the direct current, which flows in one direction, into alternating current, which flows back and forth very rapidly.

    This AC current is then sent through your electric/fuse/breaker box and can be used by all electrical appliances and fixtures within your home.

    What are the different types of solar inverters?

    There are three types of solar inverters available to homeowners. These types are string (or central) inverters, power optimizers inverter, and microinverters.

    Each different type of solar inverter has its advantages and disadvantages. It’s important to understand these differences, as well as the pros and cons of each solar inverter type, before choosing which is right for your solar panel system.

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    String Inverters: Pros and Cons

    String inverters, also known as central inverters, are the oldest and most common type of solar inverter used today. They work by connecting a string of solar panels to one single inverter, which converts the total DC input into AC output.

    Pros: Because string inverters are the oldest type of solar inverters, they are also the most reliable. After decades of being on the market, string inverters have had most of the kinks worked out. They are also the least expensive solar inverter option.

    String inverters are also centrally located on the side of your house or near the side of a ground-mount. This allows easier access to monitor, repair, or replace the inverter.

    Cons: While string inverters are reliable, they are also less efficient at optimizing solar energy output. Because string inverters are connected to an entire string of solar panels, shading on one solar panel will cut the power output of the entire string.

    Also, string inverters only offer total-system monitoring as opposed to panel-level monitoring. This can be a disadvantage when diagnosing issues with solar production, and it can also be unfortunate for those solar homeowners who want a more granular level of monitoring.

    Power Optimizers: Pros and Cons

    Power optimizers are located on the back of each solar panel, and they work in conjunction with a string inverter to convert DC to AC. They do this by conditioning the DC electricity from each panel and sending that conditioned DC to the string inverter to convert to AC electricity.

    Pros : Because power optimizers can condition the DC electricity produced by each individual solar panel, they can decrease the impact of shading on individual panels. If one solar panel is partially shaded, it will not degrade the output of the entire string as with a simple string inverter setup.

    Power optimizers also have the benefit of allowing panel-level monitoring, along with system-level monitoring thanks to the string inverter. This means any issues with solar output can be diagnosed more easily, with each solar panel being monitored individually. It also allows the homeowner to see a more detailed level of monitoring.

    Cons : Power optimizers are more expensive than using just a string inverter, but they are still less expensive than microinverters.

    Power optimizer systems also require additional power optimizers and potentially additional string inverters if you expand your solar panel system in the future.

    It is also important to note that because power optimizers are located on the roof, it is more difficult to repair and replace them if they would happen to have any issues.

    Microinverters: Pros and Cons

    The final type of solar inverter is the microinverter. Microinverters are the latest in solar inverter technology, and they work by converting DC to AC directly from the back of each solar panel. No string inverter is needed because each microinverter takes care of DC conversion on the spot.

    Pros : Because each microinverter is handling the conversion from DC to AC on each panel, that allows the system to be minimally impacted by shading on individual panels. If shade covers one panel, only that panel will produce less power output as opposed to the whole system output decreasing, as in a string inverter setup.

    Microinverters are also easy to expand with your solar system in the future. Any solar panel that is added to the system just needs to have a microinverter installed on the back of the panel.

    Similar to power optimizers, microinverters also allow for panel-level monitoring of the solar system, allowing any solar output issues to be diagnosed more easily and accurately.

    Cons : Microinverters are the most expensive of the solar inverter options. However, their benefits can easily outweigh the costs in certain situations, especially if shading is an issue.

    And because microinverters are installed on the back of each solar panel, it is more difficult to repair or replace any microinverter that might have issues.

    What Type of Solar Inverter Is Right FOr You?

    Depending on your situation, one type of solar panel might be better for you than another. If you are looking for a wallet-friendly solar inverter, a string inverter might be a good option. However, if you have the potential for shading on your solar panels, power optimizers or microinverters might be a better option.

    Contact Green Ridge Solar today to find out which solar inverter is right for you. Our solar experts can explain all the pros and cons, as well as provide a free solar analysis.

    Blog

    Reviews and information on the best Solar panels, inverters and batteries from SMA, Fronius, SunPower, SolaX, Q Cells, Trina, Jinko, Selectronic, Tesla Powerwall, ABB. Plus hybrid inverters, battery sizing, Lithium-ion and lead-acid batteries, off-grid and on-grid power systems.

    September 10, 2022 Jason Svarc

    Choosing the best off-grid solar system is not easy as off-grid systems are many times more complicated than common grid-connected solar systems. In this article, we highlight some of the many considerations which must be taken into account and discuss the various off-grid system types available. We also explain why a good quality inverter-charger is vital to building a reliable off-grid system. Finally, we will dive into the different brands available and determine which systems are best suited to different applications.

    Many people believe off-grid solar systems can be easily put together. This may be true in the case of a small caravan or cabin, but in reality, larger off-grid systems used for homes and businesses need to be carefully designed by an experienced solar installer or system designer.

    The 5 main parts of an off-grid system

    Off-grid system types. AC or DC-coupled

    Off-grid systems are built using either AC or DC-coupled power sources. AC-coupled generation sources include common solar inverters, wind turbines or backup generators (gen-sets), while DC-coupled sources include MPPT solar charge controllers or micro-hydro systems.

    Whether a system is AC or DC-coupled is generally based on the size of the system. Most small-scale systems are DC-coupled and use efficient MPPT solar charge controllers. Larger off-grid systems can be either AC or DC-coupled depending on the type of off-grid inverter-charger used, and compatibility with different solar inverters (AC) or solar charge controllers (DC). Most modern inverter-chargers can be both AC and DC-coupled, which creates a very secure, flexible power system with multiple charging options and can enable black-start operation if the main inverter shuts down, the backup generator fails or the batteries are depleted.

    Small DIY off-grid solar systems

    Small-scale off-grid solar systems and DIY systems used on caravans, boats, small homes and cabins use MPPT solar charge controllers, also known as solar regulators, which are connected between the solar panel/s and battery. The job of the charge controller is to ensure the battery is charged correctly and more importantly, not overcharged. Most small 12V/24V solar charge controllers also have load output terminals which are often used for simple DC lighting circuits. In small DIY systems, simple ‘plug-in’ style inverters are used to provide 240V or 120V AC power. These are available in many different sizes, from tiny 150W inverters up to 3000W or higher.

    Note: Small-scale, low-voltage systems can still cause damage or serious injury if not installed correctly. we recommend all systems are installed by a trained, licensed solar or electrical professional.

    DC-coupled solar charge controllers have been around for decades and are available in two main types, PWM and MPPT. Learn more about solar charge controllers here, plus how to size small-scale off-grid solar systems correctly. powerful MPPT Solar charge controllers up to 100A are used on larger scale off-grid solar power systems. These are a very efficient and reliable way of charging and managing high-capacity lithium or lead-acid battery systems.

    Key considerations when sizing off-grid solar systems

    • Daily average energy consumption (kWh). Summer and winter
    • Peak load (kW). The maximum power drawn from loads
    • Average continuous load (kW)
    • Solar exposure. Location, climate, orientation shading
    • Backup power options. During poor weather or shutdown

    With the above considerations in mind, the key component of an off-grid power system is the main battery inverter-charger often referred to as a multi-mode inverter as they can usually operate in both off-grid or on-grid modes.

    Technical Guide

    Recommended for solar professionals. See our Technical guide to selecting and sizing off-grid and energy storage systems.

    A solar professional should be able to put together what is known as a load table to help determine which type and size inverter is best suited to your individual needs. A detailed load table is also required to size the solar array, battery and backup generator.

    High-performance off-grid solar system using a Victron Quattro inverter/charger, Lithium battery system, DC-coupled with two MPPT solar charge controllers

    Lead-acid batteries

    Until around 3 or 4 years ago, lead-acid deep cycle battery systems were the most common and reliable option for off-grid systems. Lead-acid batteries are a proven technology and can last 15 or more years if they are not held at elevated temperatures (above 40 degC), and are not regularly discharged too low. Lead-acid batteries require precise battery charging following a specific charge cycle plus temperature sensors to adjust voltage settings. Most well-known off-grid inverter-chargers offer programmable charge voltage settings along with sensors to precisely charge under all conditions. Lead-acid deep cycle batteries are still used and offer several advantages over lithium as outlined below.

    One of the most significant benefits of lead-acid batteries is unlike modern lithium batteries; the battery will not shut-down at a low voltage or low state of charge (SOC). This is important, especially in emergencies or when a backup generator fails. Lead-acid batteries can be discharged down to 0% state of charge if needed for backup, but it is not recommended as it can severely reduce the life of the battery.

    Advantages

    • Compatibility with most inverters.
    • Proven and trusted technology.
    • Safe, very low risk (sealed Gel/AGM).
    • The battery will not cutout at low SOC or low voltage
    • Long life (if not over discharged)
    • Easily recycled

    Disadvantages

    • Low round-trip efficiency. 75% to 80%
    • Low energy density. Very heavy
    • Usable capacity limited. Max 40% DoD on a regular basis
    • Not modular. Fixed size once installed
    • Cannot sustain a partial state of charge for long periods
    • High temperatures can drastically reduce battery life

    Cutout voltage SOC based on inverter settings and rate of discharge.

    Lithium-Ion

    Over the last few years lithium-ion battery systems have become extremely popular due to their high round trip efficiency (92% to 98%), compact size, lightweight and scalability. In contrast, lead-acid battery banks have a fixed size or capacity whereas lithium systems do not suffer this limitation. This flexible sizing allows for additional capacity to be added at a later stage, which is a real bonus for both installers and customers alike.

    Lithium batteries have a much higher energy density compared to lead-acid and are therefore lighter and more compact. A huge advantage of lithium is the ability to sustain a low state of charge (partial state of charge) for a prolonged amount of time without any negative effects such as sulfation which is a common problem with lead-acid batteries. Also, extremely high charge rates can be achieved using lithium with charging times up to 70% faster than lead-acid.

    Also, see our complete solar battery review. A detailed comparison of the latest lithium batteries from the leading manufacturers.

    Advantages

    • Very high round trip efficiency. 92% to 98%
    • Very high energy density. Compact and Lightweight
    • High charge and discharge rates allowed
    • No degradation issues with partial state of charge
    • Modular and scalable systems (upgradable)
    • Safe and low risk (if charged correctly), in particular LFP cells.
    • Most lithium batteries come with a 10 year warranty

    Disadvantages

    • Can shutdown at high temperatures (45 degC)
    • Can shutdown at low temperatures (below 5 degC)
    • Can ‘trip off’ under continuous high surge loads.
    • difficult to recycle at end of life.
    • May not function without a compatible inverter (CANbus)

    Off-grid Lithium Batteries

    Managed lithium

    The Pylontech US series and BYD LVL Premium series are popular managed lithium batteries used for grid-connected or off-grid systems as they are compatible with a wide range of hybrid and off-grid inverters including SMA and Selectronic, and Victron. See the full list of managed lithium battery options here.

    Self-managed lithium

    There are several self-managed lithium battery options available that also contain a BMS but do not require a communication connection (such as CANbus) with the inverter in order to operate. Most self-managed batteries are modular and able to be scaled to create very large capacity battery banks (up to 500kWh). Popular brands include Simpliphi, GenZ, Discover AES and Powerplus Energy. Much like managed batteries, the internal BMS is used to monitor the state of charge, temperature and cell voltages. Another advantage of this type of battery system is it can be easily retrofitted and used to replace existing lead-acid battery banks since they do not require any special communications or connections. In the event of a system shut down or system black due to a low state of charge or low voltage, most self-managed batteries will restart automatically and do not require manual activation or reset to restart operation.

    best Lithium off-grid batteries

    In my direct experience and based on feedback from many professional off-grid installers, self-managed lithium batteries are generally the most reliable choice for off-grid systems. Managed lithium batteries are also a very good reliable option but can be problematic as they rely on communications which can become unstable, especially at a low state of charge and low temperatures. Most self-managed lithium battery systems are compatible with almost all off-grid inverters; they are also very modular, do not require communication cables and can be expanded to create larger capacity energy storage systems that are better suited to off-grid systems. Additional capacity can also be added at a later stage if required. Self-managed lithium batteries can also be used as a ‘drop-in’ replacement for older lead-acid batteries and are compatible with most inverter-chargers and MPPT solar charge controllers.

    The recommended self-managed lithium (Lithium Ferro Phosphate) batteries from the leading battery manufacturers include Simpliphi, GenZ, Discover AES, PowerPlus Energy and Zenaji Aeon.

    Lead-acid Batteries

    In specific applications, high-performance lead-acid batteries are still an excellent choice for off-grid systems. Lead-acid is a well-proven and reliable technology that is compatible with virtually all off-grid inverters and solar charge controllers. Lead-acid battery banks can also be more reliable in some situations as the battery will not automatically shut down in extreme temperatures or when a low state of charge is reached. In addition, they can be easily recycled using existing infrastructure.

    battery Inverter-chargers

    Modern off-grid solar systems use battery inverters-chargers to manage batteries, solar, and backup power sources such as a generator. The inverter-charger is the heart and brain of an off-grid system. Its primary job is to supply pure sine wave AC power, and it must be able to meet the power requirements of the appliances under all conditions. Inverter-chargers sometimes referred to as multi-mode inverters, are the central energy management system and can be either AC-coupled with solar inverter/s or DC-coupled with solar charge controller/s.

    When designing an off-grid power system, the battery inverter-charger must be adequately sized and selected according to the appliances it will be running. Some equipment such as water pumps, fridge compressors and air-conditioning units require very high surge (peak) power during startup, and this is where many cheaper inverters can fail. If multiple appliances are running at the same time, the inverter must also be able to supply continuous power under all conditions including higher temperatures. If high temperatures and high loads are common, the inverter must be sized correctly to account for temperature de-rating. Again this is where cheaper (transformerless) inverters can often trip, especially during high summer temperatures. Learn more in our technical guide to selecting an off-grid inverter.

    Best off-grid inverter-chargers

    Here is our list of the leading off-grid inverters on the market based on reliability, service, continuous and peak (surge) power rating, energy management software, AC source control, flexibility and remote monitoring.

    These inverter-chargers are all available in a range of different power output ratings (kW) to suit different applications depending on the continuous and peak power requirements. In addition, the top 5 inverters can be AC or DC-coupled using compatible solar inverters or solar charge controllers.

    Off-grid Inverter power comparison

    Inverter-chargers are available in a wide range of sizes from 2.4kW up to 20kW and can be connected in parallel or three-phase configurations for even greater power requirements. Naturally, these powerful inverters are much more expensive than common grid-connected solar inverters or compact all-in-one hybrid inverters and can cost anywhere from 1400 to 7000 depending on the rated power output (48V inverters up to 10kW).

    Most of these inverters can supply double or more of the continuous rating for a short amount of time to handle surge power spikes from motors, compressors, pumps etc. The surge rating is critical for off-grid systems to operate under all the various load conditions expected without tripping out or shutting down unexpectedly. This output power rating can also be reduced under higher ambient temperatures.

    For more detailed information about selecting off-grid and hybrid inverters see our ‘Technical guide to sizing a hybrid inverters and off-grid power systems’.

    Selectronic SP PRO

    Best off-grid inverter. 5kW power ratings

    The SP PRO inverter-chargers from Selectronic, based in Australia, feature the highest 30-minute power rating and highest peak/surge power rating along with a wide range of control methods including relays and digital inputs and outputs which can be configured for load management or generator control. However, it’s not just hardware that’s impressive, the SP PRO also features possibly the most advanced energy management software in the industry.

    Premium quality comes at a premium price, and the SP PRO inverters are one of the most expensive options available; however, considering the high cost of off-grid systems, paying a little more is well worth it for the power and features needed for a reliable off-grid system. The impressive features and high performance, together with a leading 10-year warranty place the SP PRO at the top of our list.

    See the full Selectronic SP PRO review here

    SP PRO basic specifications

    • Type: Multi-mode Inverter-charger (AC or DC coupled)
    • Use: Solar storage, back-up (UPS), off-grid
    • Sizes available (power output): 3.0kW, 4.5kW, 5.0kW, 7.5kW, 15kW, 20kW
    • Pass through power: 15kW built-in (28kW external contactor)
    • Compatible Battery types: Lead-acid, lithium-ion, flow, sodium-ion
    • Battery System Voltages: 24V, 48V, 120V
    • 63A pass-through power rating (15kW AC) or 125A (30kW)
    • Very high surge power output (2.5 x rated continuous power)
    • Battery temperature monitoring for longer battery life (lead-acid)
    • Battery sense monitoring and a mid-string sensor for precise battery charging (lead-acid Gel and AGM)
    • Managed AC-coupling with FIMER, Fronius, and Select-Sun solar inverters
    • Very powerful software package with remote access and monitoring.
    • Unique pre-charge feature for safer startup
    • Compatible with many popular lithium battery systems
    • Generator auto start, control and monitoring
    • AC / DC coupling capability
    • Parallel and 3-phase capability
    • A separate solar inverter or solar charge controller is required
    • Full off-grid capability when used with Selectronic certified (Scert) Fronius or FIMER solar inverters
    • Additional generator contactor required if used with dual AC sources.
    • Additional Select.live unit required for remote monitoring and setup.

    Price bracket – From AU4500 (4.5kW)

    See detailed specification datasheet. Selectronic SP PRO series

    Victron MultiPlus

    Best off-grid Inverter. 2kW to 5kW power rating

    Victron Energy based in the Netherlands is a well known, international, high quality manufacture with a wide product range including battery chargers, sinewave inverters, inverters-chargers, DC/DC converters, transfer switches, battery monitors, charge controllers and more. Victron offer the most cost effective range of multi-mode inverters with a huge range of sizes including the new MultiPlus II inverters/chargers. For many applications the Victron is a great quality, lower cost option, especially for DC coupled systems. The Victron remote system options are extremely advanced and offer full remote access and control, as well as some powerful monitoring features. Victron products are also simple to setup and offer a huge range of different add-ons and configuration options.

    See the full Victron Energy Review here

    Basic specifications: (8 sizes available) plus other variations

    • Type: Inverter-charger (DC or AC-coupled)
    • Use: Solar storage, back-up (UPS), off-grid
    • Solar Array Size (Solar input): N/A
    • Sizes available (power output): 0.7kW, 1.3kW, 1.6kW, 2.4kW, 4.0kW, Update June 2021. New larger 8kVA and 10kVA now available.
    • Pass through power: 3.6kW. 11.5kW. Also a 23kW (100A) model is available.
    • Compatible Battery types: Lead-acid, lithium-ion, Redox Flow battery
    • Battery System Voltage: 12V, 24V, 48V
    • Economical Inverter-charger option
    • Med-High surge power output
    • High pass-through power capability
    • Battery temperature monitoring for longer battery life
    • Generator auto-start and monitoring available
    • AC coupling with Fronius, SMA, SolarEdge, and some Delta solar inverters
    • Dual AC outputs for non-essential loads (high-power units only)
    • Programmable software with remote access and Wi-Fi App
    • 3-phase capability parallel for higher power output
    • A separate solar inverter or solar charge controller is required
    • Victron size the inverters in kVA, not kW (ref datasheet)
    • Full capability only when used with Victron regulators and colour control panel (CCGX) and Venus GX
    • Larger capacity Quattro inverters are also available (up to 15kVA)

    Price bracket – from AUD1600 (2.4kW)

    See detailed specification datasheet. Victron Multiplus inverter specs

    SMA Sunny Island

    Best off-grid inverter for extreme environments

    SMA Solar Technology is a leading German solar energy equipment supplier founded in 1981 and is one of the world’s largest manufacturers of solar inverters. The well regarded Suny island inverters are a proven performer in harsh outdoor environments in particular sub-zero temperatures.

    See the full SMA inverter Review.

    Basic specifications: (3 sizes available)

    • Type: Inverter-charger (AC-coupled)
    • Use: Solar storage, back-up (UPS), off-grid
    • Solar Array Size (Solar input): n/a
    • Sizes available (power output): 3.3kW, 4.6kW, 6.0kW
    • Pass through power: 11.5kW
    • Compatible Battery types: Lead-acid, lithium-ion (refer to manufacturer)
    • Battery System Voltage: 48V
    • High pass through power capability
    • High surge power output
    • Battery temperature monitoring for longer battery life
    • Powerful software package with remote monitoring
    • Generator auto start and monitoring (optional)
    • Dual AC inputs (grid and generator)
    • Very good IP54 weather rating
    • AC / DC coupling capability
    • 3-phase capability parallel for higher output
    • Separate solar inverter or solar DC regulator required
    • Full capability when used with SMA or compatible solar inverters
    • External automatic transfer switch required to enable battery backup
    • When configured as a hybrid inverter, grid isolation (backup mode) is not instantaneous. 2-3 sec delay.

    Price bracket – From 3800

    See detailed specification datasheet. SMA Sunny Island specs

    Outback Power FXR VFXR

    Best small capacity off-grid inverter. Split phase, North America

    Founded back in 2001 by three power systems design engineers, Outback Power has grown to become one of the leading manufacturers of off-grid power systems in North America. The company produces an advanced range of inverter/chargers designed for off-grid residential and commercial installations, along with the highly regarded Flexmax range of MPPT solar charge controllers. In addition to the popular FXR vented VFXR series designed for off-grid use, the Radian series of bi-directional inverter/chargers were developed for advanced hybrid (grid-connected) energy storage systems.

    Basic specifications: (5 sizes available) plus other variations

    • Type: Inverter-charger (DC-coupled)
    • Use: Solar storage, back-up (UPS), off-grid
    • Solar Array Size (Solar input): N/A
    • FXR sizes available (power output): 2.0kVA, 2.5kVA, 3.0kVA
    • VFXR sizes available (power output): 2.8kVA, 3.5kVA, 3.6kVA (Modular configuration. parallel for greater power requirements).
    • Compatible Battery types: Lead-acid or lithium-ion
    • Battery System Voltage: 12V, 24V, 48V
    • Available in six models for 120VAC or 230VAC
    • Med-High surge power output
    • Pass through power capability
    • Battery temperature monitoring for longer battery life
    • Generator auto-start and monitoring available
    • Programmable software with remote access.
    • 3-phase capability parallel for higher power output
    • Separate solar DC regulator required
    • Inverters sized in kVA, not kW (ref datasheet)
    • Full capability only when used with Mate3 control
    • Larger capacity is available with parallel configuration, up to 10 inverters.
    • AC coupling is only available with Radian series inverters.

    Price bracket – from US1800 (2.0kW)

    See detailed specification datasheet. Outback FXR VFXR inverter specs

    Sol-Ark 12K 15K

    Best All-in-one Off-grid Inverter. Split phase, North America

    Sol-Ark is a relatively new US-based company that distributes an all-in-one hybrid/off-grid inverter manufactured by Deye inverter Technology Co. The inverter is available in two varieties, a 12K and 15K model and has been customised to suit the US market with many features, including dual MPPT’s, ground-fault, arc-fault and lightning protection built-in, integrated load centre with DC and AC isolators, and remote access, including monitoring. While feature-packed, it does have some compromises; the Sol-Ark inverter is transformerless, meaning it has a limited surge power rating and will struggle to power large inductive loads such as pumps and compressors. Note the real-world loads (a combination of inductive and basic resistive or heating loads) are about 20% lower than the specifications listed. Additionally, each 120V leg is limited to 4.8kW (12K model), so the loads must be managed accordingly.

    Basic specifications:

    • Type: Hybrid Inverter-charger. All-in-one unit
    • Use: Solar storage, backup (UPS), Off-grid
    • Max Solar Array Size (Solar input): 13kW (12K), 19kW (15K)
    • Power rating 12K (continuous output): 7.5kW real-world loads
    • Power rating 15K (continuous output): 9.5kW real-world loads (Modular configuration. parallel for greater power requirements).
    • Compatible Battery types: Lead-acid or lithium-ion
    • Battery System Voltage: 48V
    • Split phase. 120VAC or 240VAC
    • 200A pass-through power rating (15k)
    • Parallel capability for higher power requirements.
    • Inbuilt Ground-fault and Arc fault detection (GFD)
    • Inbuilt lightning protection (PV)
    • Integrated battery DC isolator and AC source/load isolator
    • Generator auto-start and monitoring built-in
    • Programmable software with remote access.
    • Colour touch-screen display
    • Transformerless Inverter with limited surge power rating
    • The real-world loads are approx 20% lower than the specifications listed.
    • Higher power output available with parallel configuration

    Price bracket – 12K from US6800, 15K from 8200

    See detailed datasheets. Sol-Ark 12K specs, Sol-Ark 15K specs

    Disclaimer: Solar and battery storage systems must be installed by an experienced licensed electrical professional. Modern large scale off-grid solar systems are typically high voltage and can generate and store huge amounts of energy which can result in damage, fire or serious injury if the installation does not meet all relevant regulations, standards and guidelines.

    About the Author. Jason Svarc is a CEC accredited off-grid stand-alone power system specialist who has been designing and installing off-grid solar power systems for 10 years. During this time he also taught the CEC accreditation off-grid design and installation course at Swinburne University (Tafe). Having designed, installed, commissioned and monitored hundreds of off-grid systems for households and businesses over the years, he has gained vast experience and knowledge of what is required to build a quality, reliable, high-performance off-grid solar power system.

    Solar questions?

    Visit our community discussion about off-grid systems in our solar info forum.

    Compared: Grid-tied, off-grid, and hybrid solar systems

    There are three types of solar panel systems: grid-tied (on-grid), off-grid, and hybrid solar systems.

    Each type of system has a unique setup that affects what equipment is used, the complexity of installation, and, most crucially, your potential costs and savings.

    What would be the best in your situation? Let’s take a closer look at the benefits and downsides of grid-tied, off-grid and hybrid solar systems.

    Calculate the price of solar panel installation on your home

    Grid-tied solar systems

    Grid-tied, on-grid, utility-interactive, grid intertie, and grid backfeeding are all terms used to describe the same concept – a solar system that is connected to the utility power grid.

    DC electricity generated by the solar panels is sent to the inverter, which converts the power into AC electricity. This electricity is first used to service the home loads, while all surplus energy is exported to the grid in return for electric bill credits.

    Benefits of grid-tied systems

    A grid connection will allow you to save more money with solar panels through net metering, lower equipment and installation costs, and better efficiency rates.

    Save more money with net metering

    Your solar panels will often generate more electricity than what you are capable of consuming. With net metering, homeowners can put this excess electricity onto the utility grid instead of storing it themselves with batteries.

    Many utility companies are committed to buying electricity from homeowners at the same rate as they sell it themselves. As a homeowner, you can use these payments from your utility to cancel out your electricity usage charges. by up to 100%.

    Net metering plays an important role in how solar power is incentivized. Without it, residential solar systems would be much less feasible from a financial point of view.

    Lower upfront costs and ease of installation

    Grid-tied solar systems are the only type of solar system that don’t require a battery to function. This makes grid-tied systems cheaper and simpler to install, and also means there is less maintenance required.

    You can use the utility grid as a virtual battery

    The electric power grid is in many ways also a battery, without the need for maintenance or replacements, and with much better efficiency rates.

    According to EIA data, national, annual electricity transmission and distribution losses average about 7% of the electricity that is transmitted in the United States. Lead-acid batteries, which are commonly used with solar panels, are only 80-90% efficient at storing energy, and their performance degrades with time. In other words, more electricity (and more money) goes to waste with conventional battery systems.

    Additional perks of being grid-tied include access to backup power from the utility grid, in case your solar system stops generating electricity for one reason or another. At the same time, you help to mitigate the utility company`s peak load. As a result, the efficiency of our electrical system as a whole goes up.

    Equipment for grid-tied solar systems

    There are a few key differences between the equipment needed for grid-tied, off-grid and hybrid solar systems. Standard grid-tied solar systems rely on the following components:

    Grid-tie inverter (GTI)

    What is the job of a solar inverter? They regulate the voltage and current received from your solar panels. Direct current (DC) from your solar panels is converted into alternating current (AC), which is the type of current that is utilized by the majority of electrical appliances.

    In addition to this, grid-tie inverters, also known as grid-interactive or synchronous inverters, synchronize the phase and frequency of the current to fit the utility grid (nominally 60Hz). The output voltage is also adjusted slightly higher than the grid voltage in order for excess electricity to flow outwards to the grid.

    Microinverters

    Microinverters go on the back of each solar panel, as opposed to one central inverter that typically takes on the entire solar array.

    Microinverters are certainly more expensive, but in many cases yield higher efficiency rates. Microinverters are particularly useful if you have shading issues on your roof.

    Power meter

    Most homeowners will need to replace their current power meter with one that is compatible with net metering. This device, often called a net meter or a two-way meter, is capable of measuring power going in both directions, from the grid to your house and vice versa.

    You should consult with your local utility company and see what net metering options you have. In some places, the utility company issues a power meter for free and pays full price for the electricity you generate; however, this is not always the case.

    See how much a grid-tied solar system can save you annually

    Off-grid solar systems

    An off-grid solar system (off-the-grid, standalone) is the obvious alternative to one that is grid-tied.

    For homeowners that have access to the grid, off-grid solar systems are usually out of question. Here’s why. To ensure access to electricity at all times, off-grid solar systems require high-capacity battery storage and a backup generator. On top of this, a battery bank typically needs to be replaced after 10 years. Batteries are complicated, expensive, and decrease overall system efficiency.

    Off-grid systems require large amounts of energy storage as there is no option to import power from the electric grid. As such, they are typically designed using lead-acid batteries, which are a much cheaper alternative to newer (and more efficient) lithium-based solar batteries.

    Can be installed where there is no access to the utility grid

    Off-grid solar systems can be cheaper than extending power lines in certain remote areas.

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    Consider off-grid if you’re mor e than 100 yards from the grid. The costs of overhead transmission lines range from 174,000 per mile (for rural construction) to 11,000,000 per mile (for urban construction).

    Become energy self-sufficient

    Living off the grid and being self-sufficient feels good. For some people, this feeling is worth more than saving money.

    Energy self-sufficiency is also a form of security. Power failures on the utility grid do not affect off-grid solar systems.

    On the flip side, batteries can only store a certain amount of energy, and during cloudy times, being connected to the grid is actually where the security is. You should install a backup generator to be prepared for these kinds of situations.

    Equipment for off-grid solar systems

    Typical off-grid solar systems require the following extra components:

    • Solar charge controller
    • Battery bank
    • DC disconnect (additional)
    • Off-grid inverter
    • Backup generator (optional)

    Solar charge controller

    Solar charge controllers are also known as charge regulators, or just battery regulators. The last term is probably the best to describe what this device actually does: solar battery chargers limit the rate of current being delivered to the battery bank, and protect the batteries from overcharging.

    Good charge controllers are crucial for keeping the batteries healthy, which ensures the lifetime of a battery bank is maximized. If you have a battery-based inverter, chances are that the charge controller is integrated.

    Battery bank

    Without a battery bank (or a generator), it’ll be lights out by sunset. A battery bank is essentially a group of batteries wired together.

    DC disconnect switch

    AC and DC safety disconnects are required for all solar systems.

    For off-grid solar systems, one additional DC disconnect is installed between the battery bank and the off-grid inverter. It is used to switch off the current flowing between these components. This is important for maintenance, troubleshooting and protection against electrical fires.

    Off-grid inverter

    There’s no need for an inverter if you`re only setting up solar panels for your boat, your RV, or something else that runs on DC current. You will need an inverter to convert DC to AC for all other electrical appliances.

    Off-grid inverters do not have to match phase with the utility sine wave as opposed to grid-tie inverters. Electrical current flows from the solar panels through the solar charge controller and the bank battery bank, before it is finally converted into AC by the off-grid inverter.

    Backup generator

    It takes a lot of money and big batteries to prepare for several consecutive days without the sun shining (or access to the grid). This is where backup generators come in.

    In most cases, installing a backup generator that runs on diesel is a better choice than investing in an oversized battery bank that seldom gets to operate at its full potential. Generators can run on propane, petroleum, gasoline, and many other fuel types.

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    Backup generators typically output AC, which can be sent through the inverter for direct use, or it can be converted into DC for battery storage.

    Hybrid solar systems

    Hybrid solar systems combine the best of grid-tied and off-grid solar systems. These systems can either be described as off-grid solar with utility backup power, or grid-tied solar with extra battery storage.

    If you own a grid-tied solar system and drive a vehicle that runs on electricity, you already kind of have a hybrid setup. The electrical vehicle is really just a battery with wheels.

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    In a hybrid solar system, energy generated from the solar panels is first used to service the home’s electrical loads (flow #1). After the home’s energy needs have been supplied, solar power is used to charge the solar battery (flow #2). If there is still a surplus of solar energy, it will be exported to the electric grid in return for credits (flow #3). The system pictured above shows an AC-coupled lithium battery, but hybrid systems can also be designed using either lithium or lead-acid-based DC batteries.

    Less expensive than off-grid solar systems

    Hybrid solar systems are less expensive than off-grid solar systems. You don’t really need a backup generator, and the capacity of your battery bank can be downsized.

    If your battery runs out of charge at night, you can simply buy off-peak electricity from the utility company. This will be much cheaper than operating a generator.

    Smart solar holds a lot of promise

    The introduction of hybrid solar systems has opened up many interesting innovations. New inverters let homeowners take advantage of changes in the utility electricity rates throughout the day.

    Solar panels happen to output the most electrical power at noon – not long before the price of electricity peaks. Your home and electrical vehicle can be programmed to consume power during off-peak hours (or from your solar panels).

    Consequently, you can temporarily store whatever excess electricity your solar panels generate in your batteries, and put it on the utility grid when you are paid the most for every kWh.

    Smart solar holds a lot of promise. The concept will become increasingly important as we transition toward the Smart grid in the coming years.

    Equipment for hybrid solar systems

    Typical hybrid solar systems are based on the following additional components:

    • Charge controller
    • Battery bank
    • DC disconnect (additional)
    • Battery-based grid-tie inverter
    • Power meter

    Battery-based grid-tie inverter

    Hybrid solar systems utilize battery-based grid-tie inverters, which are also known simply as hybrid inverters. These devices can draw electrical power to and from battery banks, as well as synchronize with the utility grid.

    Final thoughts on grid-tied solar systems

    The bottom line is this: Right now, for the vast majority of homeowners, tapping the utility grid for electricity and energy storage is significantly cheaper and more practical than using battery banks and/or backup generators.

    What Is a Solar Inverter and How Does It Work?

    Solar energy is on the rise. According to the U.S. Department of Energy (DOE), 3% of all electricity produced in the United States comes from solar panels. Solar panels are devices that produce electricity in response to sunlight. Solar panels, however, typically require the use of a separate component known as a solar inverter. Without a solar inverter, they won’t be able to produce usable electricity. What is a solar inverter exactly, and how does it work?

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    Overview of Solar Inverters

    A solar inverter is a component in a solar panel installation that’s designed to convert direct current (DC) electricity into alternating current (AC) electricity. Power grids, of course, typically distribute AC electricity. AC electricity lives up to its namesake by alternating its direction. It can change direction, thereby allowing it to travel across longer distances than that of DC electricity. Solar inverters are responsible for converting the DC electricity produced by a solar panel installation into AC electricity.

    Whether monocrystalline or polycrystalline, solar panels almost always produce DC electricity by default. Exposure to sunlight causes the electrons within their photovoltaic material to move around and become “excited.” This movement results in the production of DC electricity. To use the solar panel installation’s electricity in a home or building, it must be converted into AC electricity, which is the solar inverter’s job. The solar inverter will perform the DC-to-AC conversion so that the electricity can be used to power devices in a home or building.

    How Solar Inverters Work

    Most solar inverters look like small boxes. They are installed between a solar panel installation and the home or building that it powers. The DC electricity produced by a solar panel installation will enter the solar inverter where it’s converted into AC electricity. After leaving the solar inverter, the newly converted AC electricity will enter the home or business.

    Of course, there are different types of solar inverters. Some of the most common types include battery solar inverters, central solar inverters, micro solar inverters and hybrid solar inverters. Regardless, they all work by taking the DC electricity produced by solar power installation and converting it into AC electricity.

    In Conclusion

    Solar panel installations consist of more than just panels. Most of them have a solar inverter. Solar inverters are devices that convert DC electricity into AC electricity. Homes and businesses generally use the latter type of current, so solar panel installations need to a solar inverter to produce usable electricity.

    What does a solar inverter do? How solar inverters work in a PV system

    When the sun shines on your solar photovoltaic (PV) system, electrons within the solar cells start to move around, which produces direct current (DC) energy. Circuits within the cells collect that energy for you to use in your home.

    This is where your solar inverter comes in. Most homes use alternating current (AC) energy, not DC, so the energy produced by your solar panels isn’t useful on its own. When your solar panels collect sunlight and turn it into energy, it gets sent to the inverter, which takes the DC energy and turns it into AC energy. At that point, your solar electricity can power your appliances and electronics or, if you’re producing more electricity than you need, it can feed back into the grid.

    Comparing solar inverter technologies: string inverter vs. string inverters with power optimizers vs. microinverters

    All inverters have the same basic task: convert DC solar energy into useful AC energy for your home. However, there are three different solar inverter technologies that you can choose for your solar panel system, and each of them works slightly differently.

    String inverters: a standard centralized inverter

    Most small-scale solar energy systems use a string inverter, also known as a “central” inverter. In a solar PV system with a string inverter, each panel is wired together into a “string”, and multiple strings (normally up to three) can be connected to your central inverter. When your panels produce energy, it all gets sent to a single inverter, which is usually located on the side of your home, in a garage, or in your basement. The inverter will convert all of the electricity from your solar panels into AC electricity for use on your property.

    Pros: String inverters are the lowest-cost inverter option, and are a very durable inverter technology. They are also the easiest to maintain, because they are in an easy-to-access location.

    Cons: A drop in the performance of an individual solar panel (i.e., from shading) can impact the output of all of the panels on an individual string. While multiple strings can accommodate multiple roof planes on the same inverter, string inverters may not be right for more complex system designs or roofs with regular shading.

    Best for: Properties with “uncomplicated” roofs that get consistent sun throughout the day, and homeowners looking for lower-cost solar PV systems.

    Power optimizers: a panel-located option to pair with a string inverter

    Power optimizers can be thought of as a compromise between string inverters and microinverters. Like microinverters, power optimizers are located on the roof next to (or integrated with) individual solar panels. However, systems with power optimizers still send energy to a centralized inverter.

    Power optimizers don’t convert the DC electricity into AC electricity at the site of the solar panel. Rather, they “condition” the DC electricity by fixing the voltage of the electricity, at which point the electricity is sent down to the string inverter. A system that pairs power optimizers with a string inverter is more efficient than one that uses a string inverter alone in shading scenarios.

    Pros: Like microinverters, power optimizers can improve the efficiency of your solar panel system if you have a complicated roof or frequent shading; however, optimizers tend to cost less than microinverters. They optimize the output of each individual panel to mitigate the impact any one shaded panel can have, and also provide the benefit of monitoring the performance of individual panels.

    Cons: A system that pairs power optimizers with a string inverter will cost more than a system with a standard string inverter option. As with microinverters, solar PV systems that include power optimizers can be more difficult to maintain.

    Best for: Homeowners with a slightly less than ideal roof for solar who are willing to pay more to increase the performance of their solar panel system, but who don’t want to invest in microinverters.

    Microinverters: high-performance at a higher cost

    If a string inverter can be considered a “central” inverter, microinverters are “distributed” inverters. Solar PV systems with microinverters have a small inverter installed at the site of each individual solar panel. Rather than sending energy from every panel down to a single inverter, microinverter systems convert the DC solar energy to AC energy right on the roof.

    Pros: Having microinverters at every solar panel provides performance benefits, especially for systems with a more complicated design or that experience shading. Microinverters optimize the output of every panel at the panel to mitigate the impact of shading, and to allow for panel-level monitoring of your system.

    Cons: Microinverters cost significantly more than a string inverter, and can be more difficult to maintain or repair in the event of a problem because they are located on the roof.

    Best for: Systems with solar panels that face multiple directions, homeowners who want to maximize solar production in a small space, and properties that have “complicated” roofs with gables, chimneys, or other objects that can cause shade.

    Choosing the best inverter option for your home

    Now that you understand how solar inverters work, your next step is to decide which type is best for your solar PV system. Not every system-design is right for string inverters, and it’s not always necessary to pay extra for optimizers or microinverters. Ultimately, there’s no universal right or wrong answer, only what’s best for your own situation and needs.

    EnergySage has additional resources that can help you make a decision about your solar inverter options:

    • Comparing string inverters, microinverters, and power optimizers
    • Microinverters vs. power optimizers: which panel-level option is best for you?
    • Advantages and disadvantages of microinverters and power optimizers

    Additionally, browse all types of solar inverters on the EnergySage Buyer’s Guide, where you can compare inverter metrics across products like efficiency and warranties.

    While you can continue to read about the different technologies, the best way to find out which option works for you is to review actual quotes from qualified local installers in your area.

    When you register your property on the EnergySage Solar Marketplace, you can review offers that have been customized to your home and evaluate the costs and benefits of different inverter options. Customers who compare quotes on EnergySage can save 20 percent or more on their solar installation simply by evaluating all of their equipment, financing, and installer options.

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    Looking to go solar? Here’s everything you need to know in… Are solar panels worth it in 2023? Best solar panels in 2023: Top products compared Solar shingles: what you need to know in 2023 How to install solar panels

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