When asked to recommend a properly sized solar energy system for an average-sized home, many installation experts will suggest a 10-kilowatt (kW) system as their default answer.
But is a solar array with this capacity really good enough for the typical home? Or is it perhaps a little too potent?
A closer examination should reveal whether a 10kW system is the best option for the typical homeowner, and possibly whether it’s the best option for you.
Can a 10kW solar energy system power an average-sized home?
The United States Energy Information Administration (EIA) reports that in 2021, the average American residential consumer used 10,632 kilowatt hours (kWh) of electricity to power their homes .
Realistically, a well-maintained 10kW solar panel array in the prime of its life can be expected to generate between 10,800 and 14,400 kWh of electricity annually in most locations, given the amount of sunshine they receive .
The good news is that this is clearly enough to meet the needs of the average homeowner. The better news is that there is a list of sun-drenched states where a 10kW system could produce a whopping 18,000 kWh of electricity annually, at minimum .
These lucky localities include:
- New Mexico
Unsurprisingly, five of these seven are among the top ten states for solar energy consumption per capita .
How much electricity does a 10kW solar energy system produce on a daily basis?
The amount of electrical power a single solar panel can produce is directly proportional to the number of peak sun hours it is exposed to over the course of a day.
A peak sun hour is defined as 60 minutes of time in which a solar panel on your rooftop would be bombarded with 1,000 watts of energy per square meter of sunlight . In real-world conditions, a solar panel would only be exposed to one full peak hour of sunlight if it were around midday and there were no clouds in the sky. When this takes place solar panels function at 100-percent efficiency, meaning a 400-watt solar panel would produce 400 watt-hours of energy over the course of one peak sun hour.
During most of the day the sun’s irradiance will be less. In those instances what hits a panel’s surface will be measured as a fraction of a peak sun hour. So, if the sun were shining at half of its potential intensity between five and six o’clock in the evening, that would be calculated as 0.5 peak sun hours of exposure for each solar panel in a rooftop array.
Peak sun hours are generally charted on a daily basis, which means all of these fractions are added up to cover a single 24-hour time period. The final number represents the peak sun hours experienced on a particular day, and it can be used to determine how much energy a solar panel array would have produced on that day.
The mathematics of this is simple, requiring just basic multiplication. If five peak sun hours were experienced on a certain day, it would mean that a 10kW solar array produced 50 kilowatt-hours (kWh) of electricity over the course of that day (5h x 10kW = 50 kWh).
According to the latest estimates, an average American home will use around 30 kilowatt-hours of electricity a day . This means that a 10kW solar array would require just three peak sun hours a day to guarantee an adequate supply of electricity to the owner of an average-sized residence.
For a detailed information about your area, check the Global Solar Atlas. It is a detailed database, enabling you to access data on annual solar irradiation in any location around the world. It is a very useful tool to go through when considering investing in photovoltaic solar panels.
How many solar panels make up a 10kW solar system?
Solar panels in 2023 are more efficient than those manufactured in the past. Over the last few years average panel conversion efficiency has risen from 15 percent to above 20 percent, and as a result the typical power rating of a standard-size home solar panel has increased from 250 watts up to 400 watts .
This is great news for homeowners, because it means you’ll need to purchase fewer solar panels to reach the 10kW plateau than would have been necessary in the past. If you purchased solar panels rated at 400W, you’d need exactly 25 to achieve 10kW of capacity.
You could of course choose to purchase lower- or higher-capacity panels, which would alter that number in one direction or the other.
You might be interested in lower-capacity models, if the discounts on price were enough to make that your overall cheapest option. And in fact, as of 2023 solar panels in the 300 to 350-watt range are still the best sellers. Conversely, you might prefer upper-range 440W—480W panels if you were a bit short on roof space.
Monocrystalline solar panels would be your high-efficiency but higher-priced option, while less-efficient polycrystalline panels would occupy the opposite end of the solar cost spectrum .
Further reading: Best Solar Panels for Homes
How much roof or ground space will be required for a 10kW solar system?
The standard solar panel is 5.5 feet long and 3.25 feet wide. This means each one will cover 17.875 square feet of space once it has been installed.
Should you decide to install 25 400W panels, you would need at least 446.875 square feet of open roof or lawn space to make your solar array fit. However, industry professions often recommend that you keep up to 25 percent of your roof space clear when you install solar panels, for safety purposes and to ensure easy access .
If you follow this advice, you would need 594. 34 square feet of roof space for your solar panels, instead of 446.875. This would be the equivalent of a roof or ground area that was approximately 30 feet long by 20 feet wide, if that helps you visualize this more easily.
How much can you save on your electric bill with a 10kW solar power system?
The average price of electricity in the United States in December 2023 was 14.96 cents per kilowatt-hour . Meanwhile, a recent study cited by the U.S. Environmental Protection Agency (EPA) showed that the average American household consumed 10,715 kWh of electricity on an annual basis, which is an average of 893 kWh per month .
Performing the appropriate calculations, we can then determine that a homeowner in the United States who installs a 10kW solar power system could save as much as $1,603 each year on electricity bills, if they were consuming electricity at an exactly average rate.
This entire amount could be saved if the homeowner went off grid and used solar to meet 100 percent of their electrical power needs. They could accomplish the same with a grid-connected system, if net metering practices in their state allowed them to sell enough excess solar back to the utility company during peak production hours to make up for what they were taking from the grid after sundown.
The total potential for savings will vary significantly by location. Consumers living in states with higher electricity rates and/or above-average annual energy consumption levels would pay more for grid-produced power, which means they would enjoy even more savings by going solar.
How much does an average 10kW solar energy system cost?
As of February 2023, the average cost of solar panels in the United States was $2.86 per watt of capacity . At this price a 10kW solar panel array would cost you $28,600 to purchase and install, if tax credits and rebates are not included.
But they should be included. All new solar homeowners in the United States can now deduct 30 percent of the cost of their solar installations from their federal taxes, thanks to a new law passed by Congress in August of this year that increased the Federal Renewable Energy Investment Tax Credit from its previous level of 26 percent .
That would amount to a savings of $8,580 based on the average cost of a 10kW solar array, which would drop the total price to $20,020.
In some states, including California, New Mexico, Rhode Island, New Hampshire, and a few others, you can receive additional tax credits of between $1,000 and $6,000 for installing solar panels, reducing your costs even further . In the most generous states you could literally cut the purchase and installation price of your solar energy system in half.
How long does it take for a 10kW solar photovoltaic system to pay for itself in energy savings?
As established during a previous calculation, the average homeowner could conceivably save more than $1,603 each year by installing 10kW worth of solar panels on their rooftop. Putting the numbers together, it would take you, as the embodiment of that average homeowner, 12 years to pay off the price of your solar photovoltaic system in full.
This assumes you’ll be investing in the neighborhood of $20,000 to cover the total cost of your solar equipment installation project, as would be expected if you were taking your federal tax credit. If you live in a state where energy prices are higher, or are using more than the typical 893 kWh per month, your payoff time could be faster, possibly dropping below the magic 10-year mark if your savings were significant enough.
Even if it took you the full 12 years to pass the payback threshold, it should be noted that this period is less than half the lifespan of the typical solar panel array, which can be expected to last from 25 to 30 years with proper maintenance .
What size battery storage do I need for a 10kW solar system?
With a 10kW solar energy system, you might very well have the opportunity to go completely off-grid to power your home. To do so, however, you’ll need to connect your system to a battery bank, so you can store energy for use during those times when sunshine is unavailable or weak (at night and on cloudy or rainy days).
To determine your battery needs, you have to first divide the amount of energy you plan to store (in watt-hours) by the voltage of the battery (48 or 24 volt batteries would be standard). The answer to this equation will be expressed in amp-hours, which quantifies the amount of energy a battery would be able to discharge while in use. This will tell you how many batteries you need to include in your battery bank .
If you want to store enough energy to cover your electricity needs for three full days (a decent standard for a fully off-the-grid system), and you use 30 kilowatt-hours of energy each day (a typical amount for the average homeowner), you’d need a battery backup system capable of storing 90kWh worth of energy. This translates to 90,000 watt-hours, and it is this number you would divide by the voltage of your battery (to generate an answer in amp-hours).
So if you planned to purchase either 48-volt or 24-volt solar batteries, you would perform one of the following calculations:
90000/48V = 1875 amp-hours, or 90000/24 = 2750 amp-hours
In the first instance, you could meet your storage needs by purchasing five 48-volt solar batteries with a 400 amp-hour capacity (2000 amp-hours provided in total), or eight of these batteries with a 250 amp-hour capacity (multiple amp-hour options are available).
If you wanted to install a battery bank of 24-volt batteries, you’d need 10 batteries if they had an amp-hour production potential of 300 amp-hours each (300 x 10 = 3000, which is greater than 2750).
If you stay connected to the grid, you won’t need a battery bank. But some solar homeowners will add a battery or two to their solar energy system anyway, as a hedge against power outages or as a way to avoid using grid-produced electricity during more expensive peak hours.
With solar power, personalized solutions offer the best value
When you install solar panels on your rooftop, you should do so with a clear idea of what you’re hoping to accomplish.
If you’re interested in lighting, healing, and cooling a garage, studio or work shed, your equipment requirements will be fairly limited. If you plan to install a grid-tied system that will meet only 40 to 50 percent of your electricity needs, with the grid taking care of the rest, your solar array can be of modest size, and if it ends up performing either better or worse than you expected, it won’t have that much of an impact on your bank account.
But if your goal is to meet 100 percent of your electricity needs through solar, the stakes will be higher and your needs more precise. You’ll have to make a significant investment in solar panels in order to achieve that goal, and that’s why you’ll want to get it right the first time.
If your rooftop panels come up short, you may be forced to spend extra on expensive and time-consuming upgrades. On the other hand, if your solar array features notably more capacity than you really need, your upfront investment will have caused you unnecessary financial pain.
To avoid costly miscalculations, you should consult with solar installation professionals who can give you an accurate and detailed estimate of your home’s year-round energy requirements. They may very well tell you that a 10kW system is the perfect size for residence, but whatever they say you should rely on their expertise to guide your decision-making processes.