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How Many Solar Panels Are Needed To Power A House?

Learn how to calculate how many solar panels you need to power your home. Includes a helpful formula for calculating how many solar panels are required.
Solar Panels
10 minutes
Written by:
Joey Cheek
Updated on:
November 11, 2022

As concerns about the future of the planet and the harm of the climate crisis weigh heavily on the minds of conscientious consumers (as do rising utility bills and electricity bills), solar power and solar panels are gaining momentum. Solar power is a viable alternative to the dangerous, toxic, and unsustainable methods of energy production upon which the world has too long relied.

Every new natural disaster and change in the seasons makes it harder for people who care about the environment to reduce their carbon footprint. We clearly can't go on as we have been, right? With how much electricity the average family uses, many solar experts believe that solar panels are our best way forward. We need a better way to produce energy and to create sustainable energy usage. The planet can't sustain our current mistakes. The benefits of installing a solar system or solar array are numerous.

But no matter how much solar energy catches our attention or how clear it is that solar panels are good for consumers and the environment, it can still be hard to find the information you might need to decide to go solar.

These questions have long stymied the process for consumers interested in beginning the process of going solar. Thankfully, SmartSolar.org has been working to make information more accessible so that interested consumers can feel secure in gathering the information required to make a good decision for their planet, wallet, and family.

Getting Started With Solar Power

As you begin to think about moving forward with solar panels for your home or wondering how many solar panels you need, you might do some cursory research. 

Below, we break down some of the primary questions you will likely be able to answer without having to undergo a site visit or work directly with a solar professional—putting the power back in your hands.

Learn how to calculate how many solar panels you need, what your estimated solar panel wattage should be, what your present electricity usage is (and how that usage relates to how many solar panels you need), and more.

First Things First: Doing The Math

While lots of solar energy companies rightfully spend a lot of time both touting how efficient their products are while also explaining how they work/create energy, that information doesn't help you make a financial decision. There's a lot you can do to cut through the fog of marketing materials and get the necessary information needed to start solar panel installation. For example, one of the most common questions consumers ask while investigating going solar is simply: “How many solar panels will I need?”

Deciding on several solar panels is a big concern and makes total sense as a point of entry. You can't get enough information on pricing or how much energy your panels will provide if you don't know how many panels you'll have.

The good news, though, is that, usually, with a calculator, you can have a good estimate of how many panels you will need to power your home. And because websites usually do list prices per panel, some simple multiplication will get you far in understanding the basic price breakdown.

Be Your Own Detective

Here are the things you'll need to know to make an educated assumption about how many panels your home might need:

  • How much energy does your house typically consume?
  • How much space on your roof can be used for solar panel placement?
  • How many hours of sunlight does your rooftop get per day?
  • What will the wattage and relative photovoltaic (PV) solar panels you're considering be?

Calculating Your Energy Consumption

Your home's energy calculation should include the kilowatts that power everything from your washing machine to the lights to the television to your PS5. The United States Energy Information Administration 2021 report states that most U.S. residential utility customers use just under 11,000 kilowatt hours (kWh) per year (just under 900 kWh per month), which can vary from family to family and house to house.

Thankfully, this information is pretty easy to get by looking at your energy bills from the past year. You'll want to be mindful that energy changes from season to season, so your current month's bill can't serve as a representative snapshot.

If You've Lived In Your Home One Year or More

If you've lived in your home for over a year, you may want to see if your utility company provides a yearly summary of your electricity consumption. If they don't, find your highest-consumption month (usually winter, when we need appliances or lights turned on earlier and more heating devices) and multiply it out by twelve to get an estimate of yearly use. 

If You're a New Homeowner

Reach out to your realtor. As part of your house's MLS listing, you should have access to energy reports for at least the past twelve months.

Once you know how much energy your home uses per year, it's time to investigate the energy production of the solar panels you're considering.

Solar Panel Energy Production

Most solar panels produce 250–400 watts of power. If possible, you'll want to get as close an estimate as you can of the amount of energy produced by the particular brand you're considering.

Additionally, there's very rarely a clear 1:1 ratio of how much energy many solar panels produce and how much energy you'll get to use from that panel. It's more likely that a 10 kW system will produce something like 14 kWh of electricity, which comes out to be a 1.4 (14/10) ratio. So you'll want to adjust your calculations to fall somewhere around there for your expected needs, knowing that most solar panels will perform somewhere in the range of the calculations below.

Use this formula to calculate how many solar panels you need to power your home: 

Number of panels = system size/production ratio / panel wattage. 

Figure Out What You're Working With: Roof, Weather, etc.

Use a conversion chart to be able to estimate the square footage of your home's energy use. You may still need to attempt to measure your roof or ask a professional to do so to learn just how much roof space you have available. Not every inch of your roof can be dedicated to solar panels. 

Plus, some rooftop areas are more often in the shade than in the sun, making them a poor choice for solar panel installation. Do you have an unusually shaped roof? Your needs might then be different from the average American household. An unusual roof shape may necessitate fewer panels—and thus more efficient panels if you still want to generate enough energy output for your home’s usage.

You'll also want to think about the weather and climate where you live. Is it often sunny? Cold? Do you get extreme weather like hurricanes or severe storms often? There are several environmental factors to consider.

You Know Your Home Best

This is where your expertise as a homeowner comes into play. You are familiar with your home, the weather in your region, the peak hours of sunlight, your monthly energy usage, your electricity bill, and your utility bill.

That knowledge is power when deciding on how many solar panels you need, what type of solar panel system to install, what your total solar panel wattage needs to be, and how intense your panel efficiency needs to be.

Another consideration you'll want to take on board as you begin to investigate your solar options is whether or not you'll want your house's panels to be “on the grid” or “off-grid.” On-grid panels are more popular than off-grid because they connect to public utility lines; that means that if/when your panels can't provide sufficient energy for your home, you'll still be able to draw on public utility.

No matter how much solar power the average solar panel can generate or how much energy even high-efficiency solar panels provide, there may be times when your average energy usage outpaces how many watts your solar energy system can provide. Even the best estimates of your annual energy usage can't account for how much sunlight will shine down in the years to come or how much power you'll need to address your annual electricity usage.

Installing solar panels requires some level of estimation of how much energy you'll need and the number of solar panels your solar systems will require. That estimate may be close; it may even be spot on. There's also a chance you'll need more solar panels installed than you initially believed, or that the solar panels or solar system you've chosen won't provide enough renewable energy for your average daily energy usage. Even the most efficient panels with high power ratings may not measure up to how much electricity you hoped they'd produce.

For this reason, it's possible to make errors when calculating how many solar panels you'll need in your solar array. Solar panel systems rely heavily on weather and circumstance for peak performance; the number of solar panels you install may not accurately reflect the number of solar panels required to match your required power rating.

While more panels equal more power, not everyone has the roof space for several solar installations. This is why many solar panel customers choose to remain on the grid: more electricity to support their actual system size, more security, as many panels as they can comfortably afford, and minimal risk of energy shortcomings.

Off-grid solar panels, conversely, are closed systems. This gives you real independence from public utilities, but can also leave you vulnerable to energy shortages. Still, if your property is particularly remote or already not a good fit for public utilities, off-grid panels are a great option. 

Risks of Off-Grid Systems

You'll want to think carefully about the number of panels, the panel wattage, your peak sunlight hours, and the number of solar panels you need to gain sufficient kilowatt-hours. If you install solar panels and only use solar power to power your home, you won't have to pay for your annual electricity use or utility bills. Many people who use solar power see this freedom as a strong reason to get their power from renewable sources.

And for off-grid solar users, there's safety in numbers: the greater the number of panels, the greater the energy output in kilowatt-hours. The more solar panels, the more energy security is. Of course, this type of dependency carries significant risk. If you make an error when trying to calculate how many solar panels you need, you may find you need more electricity than your number of panels can provide.

Joey Cheek

Consider Solar Panel Differences

So, you've calculated the size of your home and its energy usage. You've figured out how much roof space you can dedicate to solar panels. You've decided whether or not your panels will be on-grid or off-grid. Now, it's time to think about which type of panel best suits your needs.

Not all solar panels are created alike; there are three general types of solar panels available to residential consumers: monocrystalline, polycrystalline, and thin film. 

Permanent Solar Panel Options

Monocrystalline and polycrystalline panels are both silicon-based and rectangular in shape and covered by a glass sheet. While monocrystalline solar cells are cut from a single silicon crystal, polycrystalline solar cells are composed of fragments from many silicon crystals. As you might imagine, these manufacturing differences translate into price and efficiency differences. Monocrystalline panels cost more, but they also perform better and rank higher in efficiency. Polycrystalline panels are easier on the wallet but less efficient.

Flexible Solar Panel Options

Thin-film solar panels are thinner than either of the other two options above. Interestingly, the solar panel's energy mechanism itself may not be much thinner than other styles. 

Thin-film panels have a few key advantages: they're portable, and they're more flexible than their thicker siblings. However, they're also less efficient. If you're planning to move and take your panels with you, thin-film panels give you that option; they also may make it possible for you to move panels based on times of the year, etc. The tradeoff for less efficiency may be worth it to have that type of mobility. It all comes down to your needs!

Take The Next Step

Now that you’ve learned everything you need to know to contact a company for a solar panel installation estimate and take the next step in your switch to solar energy. 

Take the SmartSolar.org quiz and learn more about the benefits of installing solar panels.

Meet the author:

Joey Cheek

Joey Cheek spent 10 years on the US National Speedskating Team where he competed in two Olympic Games, winning gold, silver, and bronze medals. He attended Princeton before diving into the startup and tech world. In 2011 he launched a livestreaming platform for sports before leading a team of engineers building next-gen news and content apps for Fortune 100 companies. He is the CEO and co-founder of SmartSolar.org, whose mission is to move the earth to cheap, abundant, carbon-free energy.

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