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.
Go Solar
Solar and other types of onsite renewable generation can add up to savings. But since it’s based on your rooftop characteristics, your electricity use, and available tax credits and incentives, take time to assess what it means for you.
Check out these resources to help guide you through the process and browse our FAQs to get answers to the most commonly asked questions.
Solar Energy
The future of solar is bright in Georgia, and we are leading the way in making our state a national leader in solar energy. To help meet our customers’ growing electricity needs, we’re committed to using reliable, cost-effective and renewable energy sources that work best in our state.
Business Solar Solutions
To help meet our customers’ growing electricity needs, Georgia Power is committed to using reliable, cost-effective, renewable energy sources that work best in our state.
What solar solution is right for you?
Use our solar adviser tool to explore considerations and estimated costs for a solar panel installation on your home. Get real life figures to help you determine the best solar program for you and your goals.
Two ways to get solar energy
Solar Electric Power
In this approach, electricity is converted directly from solar energy through solar cells known as photovoltaic cells – photo for light and voltaic for energy.
Normally mounted on the roof or in a location with maximum sun exposure, the photovoltaic (PV) array components convert energy from the sun into electric current to power appliances and other household devices.
A PV system requires little maintenance and can produce power for more than 20 years.
Solar Thermal Energy
Heating water using electricity can make up 14-25% of the average home’s utility bill. A residential solar water heating system can be designed to meet between 50 and 80% of a home’s water heating requirements.
A solar water heating system requires collectors to absorb the sun’s energy and a storage system to hold the energy until it is needed. The systems used to store thermal energy are similar to conventional water heaters. The heated water is circulated through the home or building using pumps.
Georgia’s Solar Potential
The potential for solar energy use in Georgia is dependent upon the amount of sun shining on the earth’s surface called solar insolation. Several factors such as weather patterns, humidity and haze can affect local insolation levels.
As can be seen on this solar map, insolation values in Georgia are significant enough to support solar energy systems in our state, with the southern two-thirds of Georgia having solar insolation values equivalent to most of the state of Florida.
What to know before you start shopping for solar panels
There’s fierce competition in the booming residential solar industry. Solar companies employ a variety of sales strategies, from in-house sales teams to third-party companies. Tesla’s solar arm relies solely on online inquiries. While there are industry guidelines for consumer protection, tactics vary from company to company and, as the report from Detroit showed, they can verge on dishonesty. Going in with a strong understanding of some key solar topics can help you spot when a salesperson is flouting those guidelines.
The federal solar tax credit
Salespeople are likely to tout the federal solar tax credit. When you install solar panels (and certain other related technology) you receive a portion of the cost back on your taxes. For 2023, the portion you get back is 30% and will stay there through 2031 as laid out in the Inflation Reduction Act.
The tax credit isn’t a check the government will send you, or a rebate. Instead, it’s a credit you can count against the taxes you need to pay each year. To take full advantage, you’ll need to pay federal income tax and pay enough of it to match 30% of your system’s cost.
The effect of solar on your utility bill
If a salesperson says your electricity bill will disappear after installing solar and that you can kick your utility company to the curb, that could also be an exaggeration. Your bill will vary depending on your net metering agreement with your utility, your electricity usage and the base rate utility customers pay to keep up grid infrastructure. Solar panels installed and operating correctly will reduce the electricity you use and can save you a bunch of money, but the effect on your bill will vary.
Before going solar, be sure you understand how your utility compensates you for the electricity you produce. These rates aren’t necessarily set in stone. In California, regulators recently changed net metering in the state. Typically, there will be a hard deadline for any big change to net metering, and if you have your system installed before that date, you’ll receive the older (and often richer) terms.
What free solar really means
If you see ads that claim you can put solar panels on your house for free, make sure you understand what free means. Likely, it means the product advertised is either a power purchase agreement (PPA) or a solar lease. Though this means you don’t pay a large up-front cost for the panels, you will pay monthly to the company that owns them. These are legitimate services and part of the reason residential solar has exploded in the last decade. You’re likely to save more money overall with a purchase than a solar lease or PPA. Still, the low up-front cost of these two options may make solar more available and still save you money in the long run, even if the solar electricity isn’t exactly free.
With leases and PPAs, you save money if the amount you pay doesn’t rise faster than the cost of electricity from your utility.
Does your home work for solar?
Siting solar panels on your roof is another potential issue. In the northern hemisphere, panels produce the most electricity facing south, though east- and west-facing panels work too. Panels facing west might be useful in areas with time-of-use rates, where afternoon and evening solar production can offset more costly electricity.
That’s one of the biggest things when anybody wants to consider solar: Is this something that is good for your house? said McGovern, who added that a solar company had reached out to her about installing solar panels on her completely shaded roof.
If your roof is shaded, make sure an installer has a plan for addressing that. For solar to work well, you may need to cut back trees or install panels somewhere other than your roof. Your roof should be in good shape, too. Taking panels off to fix the roof likely carries additional costs. It’s important to address these issues before a contract is signed and panels are installed on your roof.
For all of these issues, any installer should give you clear answers. An installer pushing you to sign before you’ve read a contract or had all your questions answered is a red flag. If you do sign something you later regret, by law you have three days to cancel most door-to-door sales, according to the US Federal Trade Commission.
Solar sale red flags to avoid
A pushy salesperson is.- besides rude.- a sign that their sales pitch might not hold up to scrutiny.
Legitimate companies will answer your questions, McGovern said.
Here’s a quick list, from Solar United Neighbors, the US Department of Energy and others, of additional red flags and questionable claims that should prompt you to do some research.
-
The federal solar tax credit is going away soon. The federal tax credit was increased and extended in 2022. It now sits at 30% through 2032 and is slated to drop to 26% in 2033 and 22% in 2034.
Resources for getting a fair deal on solar
There are plenty of organizations, including industry groups and governments, aiming to help people go solar with the best possible experience.
- The Department of Energy: The DOE has a guide to going solar that has a long list of things to consider before settling on an installer.
- State offices: Many states run consumer protection offices with state specific advice, sometimes specifically for solar.
- The Federal Trade Commission: The FTC also offers advice on how to get a good solar deal.
- Advocacy groups: Groups like Solar United Neighbors and GRID Alternatives help people go solar. If you qualify for their programs, you may score an expert guide through the process.
- The Better BusinessBureau: The BBB grades companies based on their responsiveness to complaints. It also has an accreditation process companies can go through. Checking a company via the Better Business Bureau is a good idea, if possible.
- Certifying boards: You can find certified installers by checking with the North American Board of Certified Energy Practitioners.
- Your neighbors: If you have friends, family or neighbors who’ve had a recent solar panel installation, ask them about their experience with their installer.
Because many people haven’t had an experience with solar energy, selecting an installer can feel like a daunting task. But it’s possible to go solar and start saving money on your energy costs. There were 1 million solar installations (not just residential ones) from 2016-2019. If you plan on adding to that number, with a bit of work you can make sure it’s a positive experience.
Correction: An earlier version of this article misstated how companies get grades from the Better Business Bureau. They receive grades regardless of whether they’ve paid to go through the bureau’s accreditation process.