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Is battery storage right for you. Cheap solar battery storage

Is battery storage right for you. Cheap solar battery storage

    Is battery storage right for you?

    Try our Solar System Estimator with battery storage to help you make the best decision.

    Battery storage for homeowners

    See if battery storage is right for you.

    Customers are looking for ways to consume more of the solar energy they’re producing. By shifting your excess solar generation to peak periods such as hot summer evenings, you’re reducing your carbon emissions and the demand on the electric grid. Battery storage is a backup power source as well as a way to store your home’s solar energy for later use when the sun isn’t shining.

    Benefits of battery storage

    Environmental impacts

    By shifting your excess solar generation to peak periods, you’re reducing your carbon emissions and the demand on the electric grid, putting us closer to our goal of reaching zero carbon emissions in our power supply by 2030 – the most ambitious goal of any large utility in the United States.

    Bill saving

    A battery storage system lets you store excess solar energy generated during the day. You can use this excess energy during peak hours, when electricity is most expensive. This reduces the typical customer’s electric bill, but doesn’t factor in the cost of leasing or purchasing the battery. Learn more about our Time-of-Day rates.

    Backup power

    In the event of a power outage, battery storage systems can provide power and reliability. Unlike backup generators, battery storage can power critical appliances like your refrigerator.

    Start your estimate

    If you’re considering battery storage, use our solar system estimator, which includes a battery storage option, to help you determine the benefits of installing battery storage. Let us serve as your trusted advisor to help you make the choice that’s right for you.

    Battery storage incentives

    We have a variety of battery storage incentives available for residential customers.

    Join SMUD’s new voluntary program, My Energy Optimizer SM. and earn financial incentives for making your battery storage unit an even smarter device.

    When you partner with SMUD, your battery will reduce energy usage during the hours when demand is highest and clean energy resources are scarce. This could include shifting the time when your battery is used to power your home. The interactions would be seamless to you and no extra effort is needed on your part.

    To be eligible for the program, you must have a battery storage unit installed at your home and participate in SMUD’s new Solar and Storage Rate.

    If you’re adding a new solar system with battery storage or a battery storage system only, there is a one-time fee to connect to SMUD’s grid to recover the cost of providing interconnection service. The interconnection fee will be applied to all new systems starting March 1, 2022. Your solar installer should already be aware of this new fee. If you’re adding battery storage to an existing solar system, an interconnection fee does not apply.

    All levels of participation include a one-time incentive of up to 2,500 that is paid after the interconnect application reaches a project complete status and enrollment onboarding process is completed. The Partner and Partner program levels have ongoing performance payments. See details below.

    Levels of participation

    Starter (50/kWh up to 500)

    Set your battery to optimize with SMUD’s Time-of-Day (5-8 p.m.) Rate. Your battery is most likely already operating in this mode so you can set it and forget it. This one-time incentive is paid after the interconnection application reaches a project complete status.

    Partner (150/kWh up to 1,500)

    My Energy Optimizer Partner level allows SMUD to optimize your battery storage system to respond to Peak Events during summer months, when energy demand is highest. SMUD will communicate Peak Events in advance and your battery will respond automatically.

    When you join My Energy Optimizer Partner, you’ll participate in our Critical Peak Pricing rate. This rate is in addition to your current Time-of-Day (5-8 p.m.) Rate and gives you a discount on energy throughout the summer in exchange for higher energy during Peak Events. Customers with storage and/or solar will also receive 50 per kWh for energy sent back to the grid during a Peak Event. You’ll have battery capacity reserved for back-up power needs.

    Once enrolled, you don’t need to reconfigure your battery storage system. SMUD has partnered with the industry to make your household’s response to Peak Events seamless. The program will ensure your battery is at full charge prior to a Peak Event and that your battery discharges during the Peak Event, with no extra work on your part.

    Learn more about My Energy Optimizer programs and incentives for thermostats.

    Partner (250/kWh up to 2,500)

    The most engaged level of participation. Instead of the summer-only Peak Events in the Partner level, Partner optimizes your Tesla Powerwall year-round. The battery will continue to be available for customer use, such as back-up power needs in the event of an outage. Customers in the Partner level will receive ongoing performance payments in addition to the enrollment incentive.

    Once enrolled, you don’t need to reconfigure your battery storage system.

    For this incentive level, you must own and have installed a Tesla Powerwall.

    The Partner program is under development and will launch this summer. Check back soon.

    How to enroll

    Enrolling in one of our My Energy Optimizer programs is easy. Once you’ve installed a battery storage system, or if you already have battery storage at your home, simply use the button below to apply for the program. After receiving your application, we’ll be in touch with further instructions.

    Frequently asked questions

    Battery operation

    How does a battery storage system operate? Battery storage systems are a way of storing and releasing electrical energy in a chemical manner. Battery storage systems store the energy in batteries. An inverter converts the battery’s DC energy to AC energy your home can use.

    The battery is charged using energy from your solar PV system or the electric grid. The battery is discharged to offset energy use during more expensive peak times of the day. This is to reduce your electric bill or for back-up power in the event of an outage.

    What is the lifespan of a battery storage system? Lithium Ion (Li-Ion) battery systems usually last about 10 years. The warranty period for batteries is set by your battery system manufacturer.

    Do all battery storage systems provide backup power? Many battery storage systems can provide backup power if they are configured to do so. A battery can be configured to provide backup power for critical items or your whole home. Be sure to communicate with your contractor about how much, if any, of your battery capacity you want dedicated to backup power.

    Is battery storage safe? Safe installation should follow:

    • National Electric Code (NEC)
    • SMUD’s Electrical Service Requirements
    • Any additional requirements of your local building permitting agency

    Follow manufacturer’s care, use and service criteria to ensure safest possible operation.

    Battery storage for your home

    How long will a battery storage system power my home during an outage? Without solar, batteries usually provide backup power for about 2-3 hours at their peak rated output. When paired with solar generation, the backup period can be extended. The number of appliances powered during an outage will impact the backup power duration.

    What size battery system should I consider for my home? Your battery installation contractor can help you decide what battery system size is right for you. The typical residential battery storage system installed in SMUD territory is a 5kW / 10kWh unit.

    Can I go completely off-grid with a battery storage system? While it is possible to go completely off-grid with a battery storage system, a modern home is not designed to be disconnected from the grid. A battery storage system is not a generator. It’s not realistic to permanently operate off-grid without substantial investment in larger solar and storage systems. Even with solar generation, a storage system would need to be significantly larger to provide enough electricity to power your home 24 hours a day, 7 days a week.

    How can I learn more about battery storage systems? If you’re interested in learning more about battery storage systems, you can attend a SMUD class to get a better grasp of this new technology. Also, we recommend getting multiple bids before you sign a contract.

    Does SMUD have any requirements on how I install my battery? SMUD requires that the battery storage system installation follows:

    • National Electric Code (NEC)
    • Requirements of your local building permitting agency
    • SMUD’s Electrical Service Requirements for Distributed Generation

    The interconnection process for battery storage is very similar to interconnection of solar PV systems. Battery storage systems are processed through the SMUD PowerClerk portal. This step-by-step web tool will make your interconnection process easy and straight forward. Your contractor will most likely handle the process for you.

    My Energy Optimizer incentives

    Why join My Energy Optimizer program? Your participation in My Energy Optimizer reduces your household’s environmental footprint and helps our community achieve SMUD’s 2030 Zero Carbon Plan. The program makes it easy to conserve energy when the electricity grid is under stress. The program is also part of our efforts to reduce peak demand, avoid building new power plants and reduce the need to buy electricity from more expensive, less environmentally-friendly sources.

    Am I eligible for My Energy Optimizer if I am currently in the process of installing a battery storage system at my residence? To be eligible for My Energy Optimizer Partner and Partner, you must own the battery storage unit installed at your home and participate in SMUD’s new Solar and Storage Rate (SSR). Leased battery storage systems only qualify for the Starter level. To confirm your enrollment in the program, email

    What about back-up power? Program participants will have full access to the amount of power available in their battery storage system during a power outage. If a customer has 80% of their battery charged, then 80% capacity will be available to back-up the home. For more information, please see the Do all battery storage systems provide back-up power? question above.

    Do battery storage system installations qualify for other incentives? Battery systems charged by renewable resources may be eligible for:

    • State and federal incentives
    • Tax credits (Federal Investment Tax Credit and California Self Generation Incentive Program)

    Check with your contractor and tax advisor for more details.

    Are multi-family homes eligible for the program? Multi-family homes (including apartments, condos and duplexes) are eligible for the program; however, please note restrictions about tenants below.

    I own the home, but someone else pays the SMUD bill (like an apartment, condo or duplex). Can I sign up for My Energy Optimizer? The owner can sign up for the Starter level. Individual rental units are ineligible for Partner and Partner at this time until SMUD determines a way for owners and their tenants to mutually benefit from the program.

    Is the maximum incentive based on the number of batteries I have (i.e., one incentive per battery)? No. The maximum incentive is for the entire home regardless of number of batteries. For instance, a customer with two 2 kWh batteries would receive the same incentive as a customer with one 4 kWh battery.

    Can I upgrade to the Partner or Partner incentive if my installer enrolled me in Starter? Yes, as long as you’re eligible for the Partner or Partner level, you may upgrade and receive the difference of the enrollment incentive plus ongoing participation benefits.

    Are leased or power purchase agreement (PPA) systems eligible for My Energy Optimizer incentives? Leased and PPA systems are eligible for the Starter incentive only.

    Solar battery

    Can I add a battery storage system on an existing solar installation? Yes, you can add battery storage to existing solar installations. Your battery installation contractor will determine what’s necessary to complete a retrofit installation.

    Will I be charged an interconnection fee to add battery storage to my existing solar system? No. You will not be charged an interconnection fee to add battery storage to your existing solar system.

    Solar Battery Buying Guide: Everything You Need to Know

    Want to go off the grid or earn energy bill credits? Adding a battery to a solar panel system may be the answer. Here’s what you need to know.

    Taylor Freitas is a freelance writer and has contributed to publications including LA Weekly,, and Hospitality Technology. She holds a B.A. in Print and Digital Journalism from the University of Southern California.

    Laura Leavitt is a personal finance and wellness writer for CNET. Her work has been published at NextAdvisor, Bankrate, The Simple Dollar, MoneyGeek, Business Insider and more.

    Full energy independence isn’t achievable without solar batteries.

    Solar panels can generate electricity only when the sun is shining. But with solar batteries, you can store that energy for use at night, during an outage or to sell it back to your utility or apply as bill credits.

    Backup solar batteries run on electricity and can either work as a standalone device or as part of a home solar system. When the lights go out, your backup battery system will automatically switch on and serve as source of electricity for several hours, a day or longer.

    If people have solar as well as a battery, they can use the solar in the day to feed their houses and charge their batteries. And at night, the batteries will serve their houses instead of the grid, Kim Quirk, a branch manager at ReVision Energy, told CNET recently. It makes people a bit more independent from the grid when we tend to see big spikes.

    However, all of these benefits come at a cost. Installing a battery backup system can be a significant investment, so it’s important to understand what’s involved. For this guide, we’ve answered some of the most common questions about battery backup systems, including how they work, how they’re made, how much they cost and where you can buy them.

    How solar batteries work

    When your home doesn’t need all the energy being produced by your solar panels, the excess energy is stored in the battery. When the solar panels aren’t generating enough energy to fill the power needs of the building, the battery discharges reserve power to make up the difference.

    The way you configure your solar battery system affects how it works. You have three main options:

    • Connect to your solar panels: Batteries connected to solar panels will fill and discharge frequently in response to the times without sun that you still want electricity. This is useful when in an area that is off-grid, away from electrical utilities.
    • Connect your solar panels to a solar battery system andto the grid: You can choose to fill your battery and just keep it as a backup, rarely discharging it, and mostly selling and buying excess electricity from the electric company.
    • Use battery duringtime of use ratespikes: If you live in an area where electricity rates vary with the time of day, you can configure your system to use battery backup at the most expensive times and to buy electricity from the grid at the least expensive times.

    Benefits and drawbacks of battery backup systems

    Whether you have solar panels or not, battery backups offer plenty of benefits. For starters, they help you gain energy independence, so you don’t have to rely on the public power grid. This is especially critical if you live somewhere with frequent outages or blackouts.

    On top of that, battery backups don’t operate on fossil fuels and provide your home with clean energy. Unlike generators, they’re nearly silent to run and don’t emit carbon into the atmosphere.

    Even if the power hasn’t gone out, you can use your battery backup as a way to save money on your electric bills. For example, if you’re on a time-of-use utility plan, you can draw on the energy from your battery during peak hours rather than paying sky-high electricity rates to your energy company.

    Pros of solar batteries

    • Energy independence
    • Save money on energy bills
    • Less or no reliance on utility
    • Power your home during an outage
    • Clean energy

    Cons of solar batteries

    • Expensive, sometimes as much as a solar system
    • High upfront costs
    • Limited capacity

    Different types of solar batteries

    There are several kinds of batteries used in battery backup systems, including lithium-ion, lead-acid and flow batteries. Here’s a quick overview of each type.

    Lithium-ion batteries

    Lithium-ion batteries are the most common for home systems. Most of today’s popular battery backup products are lithium-ion, including the Tesla Powerwall, Panasonic EverVolt and Generac PWRcell. They’re lightweight and energy-efficient, making them perfect for home use.

    Lead-acid batteries

    Lead-acid batteries have been used for hundreds of years and are the primary type of battery used in cars. They’re cheaper than lithium-ion, but they aren’t as efficient, which means they’re best suited for small systems.

    Flow batteries

    Flow batteries (or redox flow batteries) are less common in home systems since they’re mainly designed for commercial use. However, the technology appears promising, and it could become more widely used in residential battery backup systems in the near future.

    Nickel-cadmium batteries

    Nickel-cadmium batteries have a high energy density with double the energy of a lead-acid battery. Nickel-cadmium batteries are very durable, expensive and work well in extreme temperatures making them a good choice for large-scale commercial and industrial projects. Cadmium is toxic, however, and generally not appropriate for residential use.

    Buying a backup battery system

    You can get battery backups from a range of businesses, including manufacturers, solar companies and battery retailers. CNET curated a list of the best batteries here. The price will depend on which battery model you choose and how many you buy for your system. According to the US Department of Energy, solar batteries can cost anywhere from 12,000 to 22,000.

    If you’re buying a battery backup as part of a solar panel system, however, you may qualify for a rebate or tax credit.

    How to set up a battery backup system

    Once you’ve decided on a battery or batteries, make sure to have it professionally installed.- otherwise, you run the risk of injuring yourself. You can expect to pay a few thousand dollars for installation (which is separate from the cost of the battery).

    Maintaining a battery backup system

    After the initial setup, there’s little maintenance required on a battery backup system. You won’t need to replenish a fuel source (like you would with a generator), and there’s no need for regular maintenance.

    Lifespan and warranties

    A few years after installation, you may notice that your battery backup system doesn’t hold a charge as well as it used to. That’s because, like other types of batteries, battery backups lose storage capacity over time.

    To account for this, battery backups include a warranty that expresses how efficient the battery should be by the end of the warranty period. Many of the top solar batteries offer 10 years and 70%, meaning that by the end of the 10-year warranty, the battery should still operate at 70% of its original performance.

    Inverters and batteries

    Inverters play an important role in how the battery stores and converts solar energy. While solar panels generate electricity in direct current, or DC, the electric grid and homes generally use alternating current, or AC. An inverter can convert AC to DC or vice versa, and most solar batteries include an inverter to store the energy in DC form, as well as an inverter to convert it back into AC to be used in the grid or the home.

    Because inversion of current isn’t perfectly efficient, battery producers are always experimenting with how to invert less often and increase the efficiency of the battery. As a result, some batteries will not have inverters for both input and output included in the system. Talk to your solar installer about the battery system you’re considering so that you can make sure you have all the external inverters you need.

    Solar Battery Costs

    Getting a solar battery is a great way for you to cut your energy bills while reducing your emissions.

    A solar battery will help you make the most out of your solar panel system, meaning you can take advantage of electricity generated in the day to use at night.

    In this guide, we’ll tell you how much you’ll typically pay for a solar battery, how soon you could break even, which government grants could help, and whether solar batteries will get less expensive over time.

    • 01 What is a solar battery?
    • 02 How much does a solar battery cost?
    • 03 When will you break even on a solar battery?
    • 04 Are solar batteries expensive to maintain?
    • 05 Advantages and disadvantages of solar batteries
    • 06 Getting the most out of your solar battery
    • 07 Are there any government grants for solar batteries?
    • 08 Will solar batteries become less expensive over time?

    What is a solar battery?

    A solar battery helps you store excess electricity generated by solar panels, so you can power your home when the sun goes down.

    Even with solar panels and a solar battery, you won’t be able to completely remove your reliance on the grid.

    You will drastically reduce how much you use the grid though, with the average household cutting its grid electricity by 73%.

    A 4 kilowatt (kW) system will typically generate 22 kW per day. and US homes usually consume 30 kW per day.

    The downside is the upfront cost and the long time it takes to break even — more on these points below.

    How much does a solar battery cost?

    You will pay 8,500 on average for a typical lithium-ion solar battery, not including installation.

    battery, storage, right, cheap

    You’ll also need to buy another solar battery before the end of your solar panel system’s lifespan, as it will last 10–15 years, compared to your solar panels’ 25-year life expectancy — bringing the total battery cost to 17,000.

    Other types of solar batteries such as lead-acid models are much cheaper, typically costing 200–400, but they are only suitable as backups for RVs and for use in small camping applications.

    They require more maintenance too and don’t have near the same capacity as lithium-ion batteries, making them bad choices to use in a home with solar panels.

    When will you break even on a solar battery?

    You’ll break even on a solar panel system that includes a battery in 18.5 years.

    A solar battery lasts 10–15 years, which is less than the average 25-year lifespan of solar panels. So you will need to purchase a second battery in a decade or so, bringing the total average cost for solar batteries to 17,000.

    Getting a 4 kW solar panel system to go with your batteries will set you back 11,080 on average, bringing the total to 28,080. That’s without the federal solar tax credit of 30% — with it, you’ll only pay 19,656 for solar-plus-storage.

    The average cost of electricity in the US is 15.42 cents per kilowatt hour (kWh), so without solar panels, grid electricity you’d spend an eye-watering 41,051 on grid electricity over 25 years — which is 1,642 per year.

    Having a 4 kW solar-plus-storage system will save you 1,062 every year on average, which amounts to 26,554 after 25 years.

    Divide the total cost of the solar panel system after 25 years by the annual savings, and you get a break-even point of 18.5 years.

    That’s a long time to wait to make your money back, but you’ll still get enormous benefits from generating your own clean electricity.

    Are solar batteries expensive to maintain?

    Lithium-ion batteries, the most popular type of solar battery for US homeowners, require almost no maintenance at all.

    Beyond a bit of light dusting and the occasional check up to make sure they’re holding charge properly, you can safely leave your solar battery alone.

    A quick note on charge: don’t worry if your battery starts to lose charge capacity over the years — this is totally normal and expected.

    You should still check that your battery’s charge degradation matches the warranty, which will guarantee you a set percentage of charge capacity after a certain number of years — for example, an 80% charge capacity by year 10.

    Advantages and disadvantages of solar batteries

    Here are the main pros and cons of solar batteries:

    Pros Cons

    Getting the most out of your solar battery

    Maintenance might be minimal, but there are other factors to keep in mind to get the most out of your battery.

    Depth of discharge

    This measures how much of your battery’s charge you should use before recharging it.

    If a solar battery has a 10 kW capacity and an 80% depth of discharge, you should only use 8 kW before recharging it again.

    And if you used all of the energy stored in your battery, that would be a 100% depth of discharge.

    You’ll typically want to avoid this, because doing so can cause the charge capacity to degrade at a faster rate than is normal.

    Many newer lithium-ion solar batteries, such as the Tesla Powerwall 2, have a generous depth of discharge between 90 and 95%.

    Battery cycles

    Each time you discharge and recharge a battery, this counts as a single cycle. Solar batteries have a set number of cycles before they start to degrade.

    Lithium-ion solar batteries are designed for daily use, much like the batteries in our phones and laptops. So you don’t need to be very careful with how often you discharge and recharge — but it’s something to keep in mind when the battery starts to reach the end of its lifespan.

    Check your warranty to see how many cycles your battery is expected to last through. If it’s 5,000 cycles, you can safely assume your battery can withstand one cycle per day for roughly 13 years.

    Are there any government grants for solar batteries?

    The Clean Energy Credit is a federal grant that gives customers up to 30% off a solar system purchase, including solar batteries, as long as the battery is charged exclusively with solar energy.

    Just install your solar-plus-storage system before 2033 to benefit from the full 30% discount, which will save you thousands of dollars.

    battery, storage, right, cheap

    If you install a solar-plus-storage system worth 28,080 — 11,080 for the solar panels, 17,000 for two storage batteries — you can save 8,424 with the Clean Energy Credit initiative and pay just 19,656.

    Getting a solar-plus-storage system installed after 2033 means you’ll only receive a tax credit worth 26%. It drops to 22% in 2034, and in 2035, the Clean Energy Credit initiative will end.

    Other state-specific solar incentives exist, so be sure to check before you make a purchase.

    Will solar batteries become less expensive over time?

    It seems like the current supply chain issues affecting metal – and a soaring demand for electric vehicles – means lithium-ion battery won’t drop until at least 2024.

    The record-high demand for lithium right now means might actually go up before they go down — a rise of 5% in the cost of solar batteries is widely predicted in the next few months.

    This leaves homeowners who are looking to buy a solar battery with a choice: either bite the bullet and invest in a solar battery now, or wait a couple of years for to stabilize or fall.

    Solar Storage Alternatives to Batteries

    The largest drawback to solar power is finding a way to store energy from day to night and from summer to winter. There are good solar batteries on the market–and they’re getting better all the time–but they’re not the perfect solution.

    Why would I need batteries?

    There’s more sun during the summer than the winter, and more during the day than the night, so solar energy is most efficient on a summer day. But maximizing solar energy potential means relying on it through a winter night. The typical consumer’s response to this problem is to purchase a rechargeable battery with their solar panel system.

    What are the drawbacks to batteries?

    Batteries are an expensive storage solution; each kWh of storage is about 400. The average annual electricity consumption for a US home is 10,972 kWh. For a home requiring this much energy, the recommended lead battery size is 73 kWh, and a lithium battery size is 38 kWh. This adds between 15,000 and 29,000 to an already expensive solar panel system.

    Additionally, batteries aren’t particularly efficient; their round trip efficiency is on average 80%, meaning that 20% of the power is completely lost as it passes through the battery. And as the energy is stored week after week, more and more of it dissipates.

    The state of California faces this exact problem in their quest for 100% renewable energy by 2045. This would require 36.3 million MWh of battery storage–7 million MWh of which is expected to dissipate over the winter. Storing this magnitude of energy would cost California about 2 trillion in various storage methods. For comparison, California currently has 150,000 MWh of storage, primarily in what is called “pumped hydroelectric storage,” which was barely enough for their goal of 50% by 2020.

    Batteries also have a limited storage. This becomes a problem–especially on the sunniest days and through the summer. But because the problem is so widespread, scientists are actively seeking a solution.

    While batteries are currently the primary energy storage unit available to the typical consumer, there are other options which are quickly rising through the ranks.

    What are the energy-storage alternatives to batteries?

    Thermal storage deposits energy in heated or cooled water, molten salt, or rocks.

    Thermal storage units heat water, salt, or rocks with any excess energy produced by solar panels. They then store the heated medium in insulated containers. When the energy is needed, the heat is removed and transformed into electricity in a process similar to the one used by air conditioners.

    Good news: thermal storage is available to consumers! It costs about 30 per kWh, as compared to a minimum of 400 per kWh for batteries. And where batteries had a round-trip efficiency of about 80%, thermal energy storage has an efficiency closer to 99%. These impressive numbers make thermal storage an attractive alternative to batteries.

    Thermal storage systems aren’t mass-produced to the level that batteries are, but they are available.

    battery, storage, right, cheap

    Power to gas (P2G) u ses energy to split water into H and O molecules, converting it to hydrogen or methane.

    When solar panels produce more energy than is being used in the home, the excess energy splits the water and creates gas that is usable for power later. The gas is stored in canisters like those typically used for propane.

    This is (objectively) by far the coolest way of storing energy. Imagine a world where everything is powered by 100% renewable compressed gas! Unfortunately, as of 2018, this energy storage option was used primarily in research and pilot facilities (mainly in Germany), so it may be a few more years before it is commercialized.

    While P2G is currently more expensive than batteries, it doesn’t lose charge over time like batteries do, transfers easily, and would fit nicely into our existing gas-driven infrastructure.

    Flywheels p erpetually spin metal rotors using energy.

    When energy needs to be the stored, it powers up flywheels; the more energy that needs to be stored, the faster the flywheels spin. The rotors have as little friction as possible and are aided by magnets, so that the rotational energy of the system is maintained.

    Flywheels have a very limited amount of storage; once the flywheels reach about 50,000 rpm, they can’t go any faster and therefore can’t accept any more energy. But they are on average cheaper than batteries; for industrial purposes, they cost about 3 million per MWh. This makes them three times more expensive than hydroelectric, but up to 73% cheaper than batteries.

    Again, flywheels are not yet produced for the average consumer–they’re primarily used by NASA and similar companies–but may be heading towards mass consumption.

    Pumped hydroelectric storage stores energy in water’s gravitational potential energy.

    When the output of solar panels is more than the home needs, extra energy powers a water pump that forces water up a hill. When the energy is needed again, the water flows back down the channel and passes through turbines to create electricity.

    This kind of system currently costs more than 1 million per MWh to install, and so is primarily used by large energy farms. On such large scales, battery storage can cost up to eight times as much. Unlike batteries, hydroelectric storage systems don’t lose power over time–only a little due to evaporation, but this is replaced in due turn by rainfall.

    As the pumped hydroelectric storage system is improved and miniaturized over the next few years, it has the potential to become a viable and cheaper alternative to batteries.

    So if you’re looking for alternatives to purchasing batteries to store excess solar energy, there are many in the making. Pumped hydroelectric storage, power to gas, and flywheels are all great options if you have millions of dollars to spend. But for most of us, thermal storage is the only real alternative to batteries; it is much closer to mass production, cheaper per kWh, and more efficient.

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