How Many Solar Panels Do You Need: Panel Size and Output Factors
How many solar panels does the average house need? How many solar panels do I need for a 3-bedroom house? How many solar panels do I need for a 2000 sq. ft. home? These are all common questions for an aspiring solar homeowner. Determining how many solar panels you’ll need for your home requires first knowing what your goals are.
Do you want to minimize your carbon footprint? Maximize the return on your investment? Save as much money as possible?
Most people want to save money while minimizing their environmental impact.
To calculate how many solar panels you need, you need to know:
- Your average energy requirements
- Your current energy use in watts
- The climate and amount of sunlight in your area
- The efficiency of the solar panels you’re considering
- The physical size of the solar panels you’re considering
One simple way of answering the “How many solar panels do I need” question is to consult a professional solar installer, who can give you a free home solar evaluation.
How much solar power will you need?
To determine your home’s average energy requirements, look at past utility bills. You can calculate how many solar panels you need by multiplying your household’s hourly energy requirement by the peak sunlight hours for your area and dividing that by a panel’s wattage. Use a low-wattage (150 W) and high-wattage (370 W) example to establish a range (ex: 17-42 panels to generate 11,000 kWh/year). Note that the size of your roof and how much sunlight your roof gets are factors as well.
If you work with an experienced solar installer, they will handle all these calculations for you. If you’re searching for a calculator to figure out “how many solar panels do I need?”, look no further. You can use SunPower Design Studio to estimate your own system size, monthly savings, and the actual appearance of a solar array on your own roof. This interactive tool provides a solar estimate in just a few seconds and can be done on your own or on a call with SunPower (800) 786-7693.
How many watts do you currently use?
Look at your electricity bill for average usage. Look for “Kilowatt Hours (or kWh) Used” or something similar, and then note the length of time represented (usually 30 days). If your bill doesn’t show kilowatt hours used, look for beginning and ending meter readings and subtract the previous reading from the most recent one.
You want daily and hourly usage for our calculations, so if your bill doesn’t show a daily average, just divide the monthly or annual average by 30 or 365 days, respectively, and then divide again by 24 to determine your hourly average electricity usage. Your answer will be in kW. (And just in case you’re wondering, a kilowatt-hour is how much power you are using at any given time multiplied by the total time the power is being used.)
A small home in a temperate climate might use something like 200 kWh per month, and a larger home in the south where air conditioners account for the largest portion of home energy usage might use 2,000 kWh or more. The average U.S. home uses about 900 kWh per month. So that’s 30 kWh per day or 1.25 kWh per hour.
Your average daily energy usage is your target daily average to calculate your solar needs. That’s the number of kilowatt-hours you need your solar system to produce if you want to cover most if not all of your electricity needs.
It’s important to note that solar panels don’t operate at maximum efficiency 24 hours a day. (See Solar 101: How Does Solar Energy Work?). Weather conditions, for example, can temporarily reduce your system’s efficiency. Therefore, experts recommend adding a 25 percent “cushion” to your target daily average to ensure you can generate all the clean energy you need.
How many hours of sunlight can you expect in your area?
The peak sunlight hours for your particular location will have a direct impact on the energy you can expect your home solar system to produce. For example, if you live in Phoenix you can expect to have a greater number of peak sunlight hours than if you lived in Seattle. That doesn’t mean a Seattle homeowner can’t go solar; it just means the homeowner would need more panels.
The Renewable Resource Data Center provides sunlight information by state and for major cities.
Now multiply your hourly usage (see question No. 1) by 1,000 to convert your hourly power generation need to watts. Divide your average hourly wattage requirement by the number of daily peak sunlight hours for your area. This gives you the amount of energy your panels need to produce every hour. So the average U.S. home (900 kWh/month) in an area that gets five peak sunlight hours per day would need 6,000 watts.
What affects solar panel output efficiency?
Here’s where solar panel quality makes a difference. Not all solar panels are alike. Photovoltaic (PV) solar panels (most commonly used in residential installations) come in wattages ranging from about 150 watts to 370 watts per panel, depending on the panel size and efficiency (how well a panel is able to convert sunlight into energy), and on the cell technology.
For example, solar cells with no grid lines on the front (like SunPower ® Maxeon ® cells) absorb more sunlight than conventional cells and do not suffer from issues such as delamination (peeling). The construction of our cells makes them stronger and more resistant to cracking or corrosion. And a microinverter on each panel can optimize power conversion at the source, in contrast to one large inverter mounted on the side of the house.
Because of these wide variations in quality and efficiency, it’s difficult to generalize about which solar panels are right for you or how many you’ll need for your home. The main takeaway is that the more efficient the panels are, the more wattage they can produce, and the fewer you will need on your roof to get the same energy output. Conventional solar panels usually produce about 250 watts per panel, with varying levels of efficiency. In contrast, SunPower panels are known to be the most efficient solar panels on the market.
To figure out how many solar panels you need, divide your home’s hourly wattage requirement (see question No. 3) by the solar panels’ wattage to calculate the total number of panels you need.
So the average U.S. home in Dallas, Texas, would need about 25 conventional (250 W) solar panels or 17 SunPower (370 W) panels.
What is the effect of solar panel size?
If you have a small or unusually shaped roof, solar panel size and numbers are important considerations. With a large usable roof area, perhaps you can sacrifice some efficiency and buy larger panels (at a lower cost per panel) to get to your target energy output. But if your usable roof area is limited, or if it’s partially shaded, being able to use fewer smaller high-efficiency panels may be the best way to make the most possible power over the long term, ultimately saving you more money.
Solar panel dimensions
Typical residential solar panel dimensions today are about 65 inches by 39 inches, or 5.4 feet by 3.25 feet, with some variation among manufacturers. SunPower panels are 61.3 inches by 41.2 inches.
These dimensions have remained more or less unchanged for decades, but the efficiency and output from that same footprint have changed dramatically for the better. In addition, SunPower designs entire systems to have virtually no gaps between panels and uses invisible framing and mounting hardware to keep the rooftop footprint as tight, efficient, and attractive as possible.
How much do solar panels weigh?
If you’re planning on installing a rooftop solar system, understanding the weight of your solar panels is another key factor to consider. Knowing a solar panel’s weight is the best way to be certain that your roof can support a full installation.
While panel weights vary from brand to brand, most panels weigh about 40 pounds.
SunPower panels are the lightest of all major brands. with some of our panels weighing as little as 33 pounds. For comparison, at the top end of the range, some conventional panels weigh as much as 50 pounds.
Summary: How many panels do you need?
Knowing the answers to the above questions will give you an idea of the ideal number of panels for your electricity generation needs — or at least a realistic range. Next, a professional installer needs to assess your roof architecture, angle to the sun, and other factors to see if and how you’d be able to physically arrange the right number of panels on your roof to achieve your daily energy production goals.
You should also consider net metering as you’re considering how much money you’ll save and make from your solar system. Net metering is how your utility company credits you for producing excess solar energy when the sun is shining and then lets you draw from those credits when you’re using a conventional power grid at night if you don’t store your excess solar energy in a battery storage system.
To get started, check out our solar power calculator, which can help you figure out how much you might save going solar.
Interested in high-efficiency solar panels for your home? Contact SunPower for more information.
- . Based on datasheet review of websites of top 20 manufacturers per IHS, as of April 2021.
- . Energy Sage, July 2021, https://news.energysage.com/average-solar-panel-size-weight/
Here Are The Different Types Of Solar Panels You Should Consider For Your Home
Lexie came from HomeAdvisor and Angi (formerly Angie’s list) and is responsible for writing and editing articles over a wide variety of home-related topics. She has almost four years’ experience in the home improvement space.
We earn a commission from partner links on Forbes Home. Commissions do not affect our editors’ opinions or evaluations.
If you’ve considered adding solar panels to your home, you’ve probably also considered the amount of money and energy you could save by doing so. The potential savings is important, of course, but it isn’t the only thing to keep in mind when it comes to making the switch—you also need to decide what type of solar panels are right for you.
Because there are several types to choose from, it isn’t as easy as simply scheduling an installation appointment.
THIS IS AN ADVERTISEMENT AND NOT EDITORIAL CONTENT. Please note that we do receive compensation for any products you buy or sign up to via this advertisement, and that compensation impacts the ranking and placement of any offers listed herein. We do not present information about every offer available. The information and savings numbers depicted above are for demonstration purposes only, and your results may vary.
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How to Decide What Type of Solar Panels to Get
The first thing to do when figuring out which type of solar panel is right for your home is to acquaint yourself with the choices at hand as well as how many solar panels you want.
According to Energy Sage, a U.S. Department of Energy-endorsed online resource that allows consumers to comparison shop for solar energy. there are three main types of solar panels available for residential use. They are: monocrystalline, polycrystalline and thin-film.
A fourth option, solar roofing shingles, is a newer and more expensive technology—but certainly a suitable (and enticing) choice for those with the budget to cover the initial costs.
Monocrystalline Solar Panels
When you picture rooftop solar panels, you probably picture monocrystalline simply because they are very commonly used. And while all solar panels offer some level of energy efficiency, monocrystalline is considered the most efficient of the bunch. How efficient? Up to 20%, Energy Sage reports, meaning that 20% of the sunshine that hits a monocrystalline panel is converted into usable energy. Monocrystalline panels are also:
- Made of an individual pure silicon crystal (in other words, the silicon comes from one source)
- Cylinder-shaped
- Uniform in color
- Durable and long-lasting (some come with warranties up to 30 years)
- Able to generate between 300 and 400 (sometimes even more) watts of power each
The downside? Monocrystalline often requires a larger upfront investment than some other types of solar panels. This is because they are more expensive to make—a cost that, naturally, gets passed on to the consumer.
And if 20% isn’t quite efficient enough for you? No worries—under the monocrystalline umbrella falls an additional type of solar panel called the PERC (passivated emitter and rear cell). While use of this technology is still ramping up, experts say it offers even more efficiency than traditional monocrystalline panels (thanks to an added layer of silicon material on the panel’s back side) and isn’t particularly cost prohibitive to manufacture.
Polycrystalline Solar Panels
Polycrystalline panels, on the other hand, are less expensive to make and therefore less expensive for the customer. The cost difference is attributed to the manufacturing process—rather than the individual silicon crystals used to make monocrystalline, polycrystalline panels are made from many different pieces of silicon that are separated into fragments and melted together.
Polycrystalline is also somewhat less efficient than monocrystalline, producing around 250 watts of power each rather than 300-plus. Physically, though, they look similar to their monocrystalline counterparts and last almost as long (warranties are in the 25-year range, but vary by brand).
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Thin-Film Solar Panels
Thin-film solar panels have a few advantages over monocrystalline and polycrystalline ones. First of all, they are comparatively lightweight. They are also malleable (the others are rigid), making them easier to install than the thicker, heavier varieties.
They are also far more affordable to manufacture than other types of solar panels and also more affordable to install.
Amorphous Silicon (a-Si) Thin-Film
Amorphous solar panels are silicon-based, like the others, but in this case, the silicone portion is just the first of three very thin layers (the second layer is heat-conductive; the top layer is protective).
Amorphous panels also do well in warmer climates because they can withstand intense heat and are more adept at generating energy on darker days (meaning the sun doesn’t have to be shining bright in a clear blue sky for them to do their job).
Unfortunately, amorphous panels don’t last as long as other types of solar panels—according to the American Solar Energy Society, you’ll only get between 10 and 20 years out of them. Furthermore, they are only around 7% efficient.
Cadmium Telluride (CdTe) Thin-Film
Produced with cadmium, which the Occupational Safety and Health Administration considers a toxic heavy metal, cadmium telluride thin-film is the second most used solar cell type in the world after crystalline cells. However, CdTes aren’t the best in terms of efficiency,
Copper Gallium Indium Diselenide (CIGS) Thin-Film
Also produced with cadmium, Copper gallium indium diselenide (CIGS) thin-film is above-average in efficiency but is very expensive. The cells place Copper, Indium, Gallium, and Selenide layers on top of each other to efficiently convert sunlight into energy.
(PERC) Passivated Emitter and Read Cell Panels
PERC (passivated emitter and rear cell) panels are a newer type of solar technology designed to be more efficient than traditional monocrystalline panels. While this technology is still ramping up, PERC panels feature silicon material on the panel’s backside to achieve higher energy conversion efficiency. They also aren’t particularly cost-prohibitive to manufacture.
Solar Panel Types by Efficiency
Monocrystalline solar panels are the front runner as the most efficient panels with 20% and up. Polycrystalline solar panels are a close competitor with 15% – 17% efficiency. While CIGS thin-film has 13% – 15% efficiency, CdTe thin-film has 9% – 11% efficiency, and a-Si thin-film has 6% – 8% efficiency.
Solar Panel Types by Cost
Although monocrystalline solar panels are the most efficient, they are also the most expensive type of solar panels, with the average cost being 1 to 1.50 per watt. Polycrystalline solar panels are next in line as the most expensive, costing 0.70 to 1 per watt. While CIGS thin-film costs 0.60 to 0.70 per watt. CdTe thin-film costs 0.50 to 0.60 per watt. and a-Si thin-film is the least expensive at 0.43 to 0.50 per watt.
Solar Panel Type by Power Output
Most residential solar panels on today’s market are rated to produce between 250 and 400 watts per hour. Monocrystalline solar panels can generate between 320 watts and 375 watts of power capacity, while polycrystalline solar panels generate ratings between 240 watts and 300 watts. Thin-film panels don’t come in uniform sizes, so there is no standard measure of power capacity. However, thin-film solar panels have a lower power output comparatively.
Solar Panel Type by Appearance
One benefit of thin-film solar panels is their sleek appearance. Labeled the most attractive of the three solar panel types, the panel’s all-black thin design allows them to lie flat against roofs, so they blend in seamlessly.
Like thin-film solar panels, monocrystalline panels have a sleek, solid black aesthetic. However, the panel’s solar cells are shaped in a unique way that causes quite a bit of white space on the panel, making them more pronounced than thin-film solar panels.
In the last place for appearance, polycrystalline solar panels look less seamless than thin-film and monocrystalline. Each polycrystalline cell is manufactured with a blue, marbled look, making each panel look substantially different from the next, making them more distinctive.
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Other Factors to Consider When Comparing Panel Types
In addition to efficiency, cost, power output and cost, there are several other factors to consider when determining which panel type is right for you. For instance, the weather in your area should undoubtedly be a consideration.
Hail Rating
Although most solar panels are protected by a thick layer of tempered glass that can tolerate severe impacts, a hail storm can present significant problems for your solar panels. Therefore, they are tested for hail impacts.
On average, solar panels are certified to withstand hail of up to 1 inch falling at approximately 50 mph. Monocrystalline and polycrystalline solar panels are ideal for areas that experience heavy hail. At the same time, thin-film solar panels are not ideal for hail since they have a thin design.
Hurricane Rating
Hurricanes are inevitable in some locations, so solar panels must withstand high winds and rain. While there is no formal solar classification rating for hurricanes, most solar panels can withstand up to 140 mph winds and are secured via fasteners, through-bolting modules, or a three-frame rail system to ensure safety through a hurricane or tropical storm.
Temperature
The temperature outside can determine how efficiently solar panels generate energy. Solar panels work best at about 77°F. If the peak temperature of your solar panels gets higher than 149°F, solar panel efficiency can decline.
Fire Rating
In the event of a fire, solar panels are required to match the fire rating of the roof where they are installed to ensure they do not accelerate the spread of flames. Therefore, solar panels now carry the same fire classification rating as roofs, such as:
- Class A: severe fire test exposure
- Class B: moderate fire test exposure
- Class C: light fire test exposure
How Do Solar Panels Work?
Before deciphering which solar panel type is right for your home, you should know how solar panels work and what to expect when you utilize them. The first thing to know is that solar panels harness the sun’s power and are an endless energy source that can perform all necessary functions. Solar panels are also able to create this energy in a manner that can save not only the planet but also your money.
Solar Roofing Shingles
Efficiency and price aside, some homeowners are hesitant to go solar for purely aesthetic reasons. In other words, they just don’t like the look of solar panels. If this is you, consider solar shingles.
Solar shingles allow you to get many of the benefits of solar panels without disrupting the look and feel of your roof. They are manufactured using the same technology as solar panels, and they are available at a variety of price points (depending on the brand).
Sadly, the cons are not insignificant. First and foremost, price is a huge concern—shingles are almost always more costly (especially if you go with a brand like Tesla, which launched a line of solar roofing shingles in 2019). Not only that, solar shingles are in short supply. So, even if you have the budget and the desire to add them to your roof, you might not be able to track them down.
Efficiency-wise, solar shingles are also only between 14% and 18% efficient, which isn’t bad compared to the less efficient amorphous panels but, on the lower end, doesn’t really seem all that great next to the monocrystalline ones.
Furthermore, solar shingles won’t necessarily work on every type of roof. Most are made to replace asphalt roofing tiles only (with some exceptions). The most cost-effective route? Coordinating overall roof replacement with the addition of solar shingles, which has a higher upfront cost, but is more likely to even out in the long run.
Which Type of Solar Panel Is Best?
Due to a wide selection of capabilities, quality, price points and features, shopping for the perfect solar panels for your home can be overwhelming. However, with some help, you can typically find the panel type that suits your home’s needs.
For instance, monocrystalline solar panels have proven to be the best solar panel type due to their 20% and up solar efficiency, although they may be the most expensive per-watt solar-type. The second most popular solar panel type is polycrystalline, which is also made of crystals but is less durable, efficient and costly to produce and purchase. Finally, thin-film solar panels are the least efficient, least expensive type and are more common in commercial applications.
Should I Get Solar Panels?
You are now familiar with your solar panel choices, but is it even a good investment? That depends. Before getting your hopes up, ask yourself a few questions:
- Do I have the right roof for solar panels? Roofs on older homes are often incompatible with solar panels, and things like skylights can also be problematic. Consult with a roofer and solar panel installer to find out for sure.
- Does My HOA allow it? If you live in a neighborhood with an HOA, the rules may or may not allow you to install solar panels.
- Do I have the money to cover the costs? Solar panels should save you money over time, but there is still an upfront investment. If you can’t afford it, the future savings might not be worth it.
- How long am I going to live in this house? If you are planning to sell your house anytime in the foreseeable future, it might be better to let the future homeowners decide for themselves whether or not to get solar panels. Otherwise, you might find yourself investing a lot of money for a benefit you don’t get a chance to enjoy (it can take years to recoup your investment).
- How much do I spend each month on electricity? Households with low energy costs aren’t going to benefit as much from solar panels as a household with large electrical bills, so be sure to run the numbers before making a decision.
THIS IS AN ADVERTISEMENT AND NOT EDITORIAL CONTENT. Please note that we do receive compensation for any products you buy or sign up to via this advertisement, and that compensation impacts the ranking and placement of any offers listed herein. We do not present information about every offer available. The information and savings numbers depicted above are for demonstration purposes only, and your results may vary.
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Solar Photovoltaic Panel System
Learn Basics of Solar Photovoltaic Panel System and How PV Panels Array Works to Generate Electricity from Solar Energy of the Sun.
Here we Learn Basics of Solar Photovoltaic Panel System and How PV Panels Array System Works to Generate Electricity from Solar Energy of the Sun.
What is a Photovoltaic Cell or Solar Cell?
A Photovoltaic Cell (PV Cell) or Solar Cell is the smallest and basic building block of a Photovoltaic System (Solar Module and a Solar Panel). These cells vary in size ranging from about 0.5 inches to 4 inches. These are made up of solar photovoltaic material that converts solar radiation into direct current (DC) electricity.
Semiconductor Materials used for photovoltaic include monocrystalline silicon, polycrystalline silicon, microcrystalline silicon, cadmium telluride, and copper indium selenide /sulfide.
What is a Solar Module
A single photovoltaic cell can produce about 1 to 2 watts of electricity. This energy is too less for use in any household or for a commercial purpose.
Therefore, an array of these Solar PV Cells (60 or 72) are electrically connected together in series to form a PV Module. A PV Module can have 60 or 72 PV Cells depending upon the requirement. This connection is done by soldering using flux cored solder wire and PV Ribbon.
What is a Solar Photovoltaic Panel?
A single photovoltaic Module can produce very little electricity. This energy is too less for use in any household or for a commercial purpose. Hence, an array of such PV Modules are electrically connected together to form a larger Solar Photovoltaic Panel. A PV Panel can have any number of PV Modules depending requirement of Solar Energy.
How Solar Photovoltaic Panel System Works to Generate AC Electricity
A Array of Solar Photovoltaic Panel System generates DC Electricity. This DC Electricity is Converted to AC using a System called “Solar PV Balance-of-System” (BOS).
The BOS System uses some equipment to convert DC to AC. Such Equipment include:
- Solar Panels to Generate DC from Sunlight.
- An inverter to convert DC to AC.
- Solar Battery to Store the electricity.
- Few other electrical wiring accessories for installation of the system to work.
The Cost of Solar Panels: Is It Worth It?
Do the benefits of solar panels outweigh their costs?
Nathaniel Riley brings 28 years of experience in financial services, including merger-arbitrage trading, hedge funds, and alternative investments.
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What Is Solar Power for the Home?
Homeowners who install solar power systems can receive numerous benefits: lower electric bills, lower carbon footprints, and potentially higher home values. But these benefits typically come with significant installation and maintenance costs and the magnitude of the gains can vary widely from one house to another.
This article will help homeowners make the financial calculations required to determine the viability of solar power in their homes.
Key Takeaways
- Those seeking to go green may want to consider equipping their home with solar panels.
- Not only is solar power good for the environment, but you can earn money selling back excess power to the grid.
- While costs have come down over the past years, installation and maintenance of solar panels can be quite expensive.
- Solar panels are best suited for homes that receive ample sun exposure throughout the year.
- Before committing to solar power, be sure to understand both the social and economic factors.
Understanding Solar Power
In principle, working out whether it makes financial sense to install solar power for your home is simple. You will need to calculate:
- The cost of a solar power system
- How much energy it will produce
- What you would otherwise pay for the same amount of energy
- How many years it will take for your upfront investment to pay for itself in saved energy costs
- Whether the system will pay for itself in five years
If it does and you have the upfront capital, it’s probably a great idea. If you’ll have to wait longer for savings or take out a loan to afford the system, you’ll need to think the decision through carefully.
In practice, however, things are not this simple. There is a large variation in each of these factors, and that can make the costs and benefits of installing solar power for two homes—even if they are neighbors—radically different.
There are some tools that can help, though. Solar Reviews offer a calculator that will quickly provide you with representative costs and savings for a solar power system in every part of the U.S. Calculators like this are a good place to start if you are new to solar energy and want to understand the basic cost model.
In the rest of this article, we’ll take you through each of the key factors you should consider when calculating the costs and potential savings of solar power for your home.
Before getting solar panels, get quotes from several reputable installers to compare.
The Cost of Solar Power for Homeowners
First, let’s look at the cost of installing a solar power system for your home. The average, upfront cost of a residential solar power system is between 3,500 and 16,000.
Why the huge range of costs? Well, a lot of the variation depends on the size of the system you’d like to install and the type of panels you want to use. Whatever system you use, keep in mind that solar power is capital intensive and the main cost of owning a system comes upfront when buying the equipment. The solar module will almost certainly represent the largest single component of the overall expense.
There are some additional costs, as well. Other equipment necessary for installation includes an inverter (to turn the direct current produced by the panel into the alternating current used by household appliances), metering equipment (if it is necessary to see how much power is produced), and various housing components along with cables and wiring gear. Some homeowners also consider battery storage. Historically, batteries have been prohibitively expensive and unnecessary if the utility pays for excess electricity that is fed into the grid (see below). The installation labor cost must also be factored in.
In addition to installation costs, there are some further costs associated with operating and maintaining a PV solar array. Aside from cleaning the panels regularly, inverters and batteries (if installed) generally need replacement after several years of use.
Subsidies
While the above costs are relatively straightforward—often a solar installation company can quote a price for these for a homeowner—determining subsidies available from the government and/or your local utility can prove more of a challenge. Government incentives change often, but historically, the U.S. government has allowed a tax credit of up to 30% of the system’s cost.
details on incentive programs in the U.S., including programs within each state, can be found on the Database of State Incentives for Renewables Efficiency (DSIRE) website. In other countries, such information is often available on government or solar advocacy websites. Homeowners should also check with their local utility company to see whether it offers financial incentives for solar installation and to determine what its policy is for grid interconnection and for selling excess power into the grid.
97.7 gigawatts
The U.S. installed 19.2 gigawatts of solar PV capacity in 2020 to reach 97.7 GWdc of total installed capacity, enough to power 17.7 million American homes.
Calculating Your Energy Production
The second factor you’ll need to consider in your calculations is the amount of energy your system will produce and when it will do that. This can be a very complicated calculation to make, even for experienced solar engineers. However, let’s run through the basics.
One of the most important considerations is the solar irradiation levels available in the home’s geographical location; in other words, how sunny it is where you live. When it comes to using solar panels, being closer to the equator is generally better, but other factors must be considered. The National Renewable Energy Laboratory (NREL) produces maps for the U.S. showing solar irradiation levels and the tools on its website provide detailed solar information for specific locations within the U.S.
Equally important is your home’s orientation: For rooftop arrays, a south-facing roof without trees or other objects obstructing sunlight maximizes the available solar energy. If this is not available, panels can be mounted on external supports and installed away from the house, incurring additional costs for the extra hardware and cables.
And then you must factor in the size of your system. Solar panel size is quoted in terms of the theoretical electrical output potential in watts. However, the typical output realized for installed PV systems—known as the capacity factor—is between 15% and 30% of the theoretical output. A 3 kilowatt-hour (kWh) household system running at a 15% capacity factor would produce 3 kWh x 15% x 24 hr/day x 365 days/year = 3,942 kWh/year or roughly one-third of the typical electricity consumption of a U.S. household.
How Much Will You Save?
Once you know how much a solar power system will cost upfront, and how much energy it will produce, you can (theoretically) predict how much you can save in energy costs per year.
This is another tricky calculation, however, because a lot depends on how you pay for electricity at the moment. Utilities often charge residential consumers a flat rate for electricity, regardless of the time of consumption. This means that instead of offsetting the expensive cost of peak electricity production, homeowners’ solar power systems merely offset the price they are charged for electricity, which is much closer to the average cost of power production.
However, many utility companies in the U.S. have introduced pricing schemes that allow homeowners to be charged at different rates throughout the day in an attempt to mirror the actual cost of electricity production at different times: This means higher rates in the afternoon and lower rates at night. A PV solar array may be very beneficial in areas where this sort of time-varying rate is used since the solar power produced would offset the most costly electricity.
Exactly how beneficial this is for a given homeowner depends on the exact timing and magnitude of the rate changes under such a plan. Similarly, utilities in some locations have pricing schemes that vary over different times of the year due to regular seasonal demand fluctuations. Those with higher rates during the summer make solar power more valuable.
Some utilities have tiered pricing plans in which the marginal price of electricity changes as consumption rises. Under this type of plan, the benefit from a solar system can depend on the electricity use of the home; in certain areas subject to rates that increase dramatically as consumption increases, large homes (with large energy needs) may benefit most from solar arrays that offset high-cost marginal consumption.
For some homes, it might even be possible to make money by selling solar power back to the grid. In the U.S., this is done through net metering plans, in which residential consumers use the power that they put into the grid (when the rate of electricity generation from the solar array is greater than the rate of household electricity consumption) to offset the power consumed at other times; the monthly electric bill reflects net energy consumption. The specific net metering regulations and policies vary across regions. Homeowners can refer to the DSIRE database and should also contact their local utilities to find more specific information.
Calculating Solar Power Costs
At this point, you will be in a position to make a final calculation, and an assessment of whether solar power makes sense for you.
The overall cost and benefit of a solar system can theoretically be evaluated using the discounted cash flow (DCF) method. Outflows at the beginning of the project would consist of installation costs (net of subsidies) and inflows would arrive later in the form of offset electricity costs (both directly and through net metering).
However, rather than using DCF, the viability of solar power is usually evaluated by calculating the levelized cost of electricity (LCOE), then comparing it to the cost of electricity charged by the local utility. The LCOE for household solar will typically be calculated as cost/kilowatt-hour (/kWh or ¢/kWh)—the same format commonly used on electricity bills. To approximate the LCOE, one can use the following equation:
LCOE (/kWh) = Net Present Value (NPV) of the Lifetime Cost of Ownership / Lifetime Energy Output (kWh)
The useful life of a PV solar module is generally assumed to be 25 to 40 years. The cost of ownership includes the maintenance costs, which must be discounted to find the NPV. The LCOE can then be compared to the cost of electricity from a utility; remember, the relevant price is that which occurs during times at or near peak PV solar production.
Is Solar Power Worth It?
Once you’ve worked through all of these calculations, you’ll likely end up with a single number—the number of years it will take for a solar system to pay for itself in savings from your energy bills. If you live in a sunny part of the country and have high utility bills at the moment, you could be looking at a system that will reach this point in five years. Other homeowners may have to wait 10 or 20 years to reach this point.
In other words, most homeowners will eventually see a benefit from a solar power system; it might just take decades for this to be realized. Whether it is worth installing such a system therefore often comes down to a number of much less technical factors than those we’ve listed above: how long you are going to stay in your home, the subsidies available in your area, and simply whether you want to do your bit for the environment.
Pros and Cons of Solar Panels for Your Home
Like most things, solar power has its benefits and drawbacks. At the same time, some economic costs may be defrayed by the social benefits to the environment and lowering your carbon footprint, which may be more important to you than a purely monetary evaluation.
- Green energy that lowers your carbon footprint
- Net metering allows you to sell back excess energy produced
- You may be eligible for certain tax breaks
- Installation and maintenance costs are still high
- Solar only works when the sun is out
- Parts of the system need to be replaced every few years
- Some tax breaks may have expired or will be expiring
Can a House Run on Solar Power Alone?
Practically, it is not often possible. This is because solar only works when the sun is shining—when it is cloudy or nighttime, they do not generate electricity. There are some battery solutions to provide power during these times, but they still tend to be quite expensive. Most homes with solar panels still rely on the grid from time to time.
Do You Really Save Money With Solar Panels?
Depending on where you live, it is possible that the system can pay itself back and more over time. This is because you won’t be spending as much money buying electricity from your utility. If net metering is in place, you could reduce your bills even further.
How Much Does a Solar Panel Cost?
have been coming down steadily over the years. The total cost will depend on how many kilowatts of power your array will generate. According to consumer reports, after solar tax credits are accounted for, the cost for a solar panel system on an average-sized house in the U.S. in 2021 ranges from 11,000 to 15,000.
How Long Will It Take To Recoup the Initial Cost?
Depending on where you live and the size of your system it can take, on average, anywhere from 10 to 20 years to break even on a solar installation.
The Bottom Line
Determining whether to install a PV solar system may seem like a daunting task, but it is important to remember that such a system is a long-term investment. In many locations, solar power is a good choice from a financial perspective.
Even if the cost of solar power is found to be marginally more expensive than electricity purchased from a utility, homeowners may wish to install solar power to avoid future potential fluctuations in energy costs, or may simply wish to look beyond their personal financial motivations and use solar for green living.