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How Many Solar Panels Do I Need on My Roof? Here's What the Experts Say

The question "How many solar panels" on top of an aerial view home with rooftop solar panels.
PublishedApril 5, 2024
UpdatedMay 24, 2024
AuthorCory O'Brien HeadshotCory O'BrienSenior Director - Growth MarketingEditorRyan Barnett HeadshotRyan BarnettSVP, Policy & New Market Development
In this article
01.
4 Factors that Impact the Correct Number of Solar Panels for Your Home
02.
How Can I Calculate the Correct Size of My Solar Panel System?
03.
The Number of Solar Panels You Need Depends on You
04.
Key Solar Panel Installation Takeaways

You'll need more than one solar panel to provide enough power to your home and most families will require several solar panels connected together into a highly efficient solar installation to meet their energy needs. But exactly how many solar panels do you need for your home?

The truth is that calculating the number of residential solar panels you need on your roof depends on a wide variety of factors, including energy use, peak sun hours, roof facing and suitability, panel output, and your solar goals.

The experts here at Palmetto have created this article to help you understand how many solar panels you will need, so you can optimize your solar panel cost and save as much money as possible, and also efficiently minimize your carbon footprint. To find the right number of solar panels for your family, we’ll investigate all the elements that go into the solar power system design process and explain how each impacts the necessary size of your solar energy system.

Whether you’re a solar enthusiast and want to learn more about the entire solar design process, or you're comparing different options to find the right number of panels for your needs, there's a lot of information here that you’ll find helpful.

See how much you can save by going solar with Palmetto

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4 Factors that Impact the Correct Number of Solar Panels for Your Home

A typical home needs 18-26 solar panels to cover 100% of its electricity usage. While there are many elements you can analyze to determine the ideal size of your future system, these four are most worth your time:

  • Your household energy consumption
  • Peak sun hours for your area
  • Output of each solar panel
  • Your solar goals

Here's a deeper look at each of these elements.

1. Energy Consumption

When people begin thinking about home solar, the questions they ask are often similar:

  • "How much energy does a solar panel produce?"
  • “How many solar panels can I fit on my roof?"
  • "How large of a solar system do I need?"
  • "How many solar panels to power a house?"
  • “What is the number of solar panels needed for my family?

When determining the number of panels you need, it all boils down to one crucial factor: The amount of energy you use (or plan to use) in your home.

To begin the process of figuring out the right number of solar panels for your house, you should first determine how much electricity you use during an average month. Start by viewing your previous utility bills. Once you locate your last twelve monthly electric bills, add up your total usage in kilowatt-hours (kWH) and divide by 12.

Both your 12-month total energy consumption and your 12-month average energy consumption are the baseline information you need about your energy consumption, because everything else depends on your electricity usage.

2. Peak Sunlight Hours

Solar panels rely on direct sunlight to generate electricity. To perform as efficiently as possible, your panels need maximum sustained exposure to sunlight, a concept called “peak sun hours." Where you live can determine how much energy your solar panels will produce in a day. For example, the American Southwest regularly receives well over six hours a day of peak sun hours, while the American Northwest struggles to get four peak sun hours on a good day.

The best way to learn the amount of sustained sunlight your area receives is to speak with a solar energy system expert, like the ones at Palmetto. Our experts can help you determine the right number of panels for your roof based on the number of peak sun hours in your area, as well as the angle at which they should be installed and additional tips that will maximize your electricity generation.

You can also consult the U.S. Energy Information Administration or use tools like the U.S. State Solar Resource Map from the National Renewable Energy Laboratory to determine peak sun hours in your area.

3. Solar Panel Output

Different solar panels have different electricity generation capabilities, based on factors that include the the number of solar cells in that panel and whether they are efficient panels. Additionally, how many square feet of space is available, a panel's installation direction, and shade from trees or a chimney may impact how much electricity your solar panels produce.

The output of each solar panel also depends on the angle of installation. Solar panels are installed in a solar array, which is just the name for a group of solar panels that are all installed together. The simplest and easiest array to install is a single rectangular shape. However, a single rectangular array requires a basic rectangular roof for suitable installation, so it’s incompatible with complex roof designs.

If your home features an unusually shaped roof that doesn’t allow for a single array that meets your solar needs, the correct number of panels for your home will instead be arranged in multiple groups in different areas of your roof. If different arrays face in different directions, their electricity output will vary due to differing exposure to sunlight, even if the panels are identical.

4. Your Solar Goals

People switch to solar for different reasons. Some want to save money on electricity costs and energy bills, others want to have a plan to avoid frequent utility brownouts or power outages, and others want to minimize their carbon footprint and be part of a sustainable energy solution that benefits everyone. Those are all good considerations to help you determine the number of panels to achieve your desired power output.

Let’s consider three common options:

  • If you plan to participate in net metering, you may want to install solar panels that can generate more electricity than you consume. This allows you to receive credits for excess electricity production and realize the maximum amount of savings on your energy costs.
  • If avoiding power outages is your goal, a good solar panel battery storage system will ensure you store enough electricity that you can use later. When the local utility is struggling, you'll have a dependable reserve of power to tap into.
  • If you want to use solar to help the planet, you will need enough solar panels to produce 100% of your electricity needs so you don’t consume dirty electricity from the utility. This option also allows you to maximize your energy savings and be protected against unreliable utilities.

Having a clear goal makes it easier for you and your solar installer to arrive at the right number of solar panels for your home, which is key to your ultimate satisfaction.

See how much you can save by going solar with Palmetto

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My electric bill is $290/mo

How Can I Calculate the Correct Size of My Solar Panel System?

Palmetto has an online solar calculator to help customers determine the size of the solar energy system they need and the correct number of panels. Try our Solar Savings Estimate tool to see how much you can save by going solar, based on your recommended solar energy system size. It's a simple but powerful tool that can help you understand your options and make the right decision for your goals.

Alternatively, you can use a simple formula to determine the size of the system you need to power your house:

(Monthly Electricity Usage / Monthly Peak Sun Hours) x 1,000 / Solar Panel Wattage

Let's break this formula down further to help you better understand what it means.

1. Determine Your Energy Consumption

Review your 12 most recent utility bills to learn your monthly consumption. Simply total the last 12 months of usage from your electricity bills and divide by 12 to get your home's average. For our purpose here, we will use 1,200 kWh per month as an example.

2. Determine How Much Sunlight You Receive in Your Area

You need to determine how many peak sun hours the average house your area receives. Keep in mind, average daily peak sun hours aren’t merely the hours when the sun is in the sky. They are the hours when the sun delivers the most sustained exposure of sunlight, which means the hours when your solar panels will be most productive.

Peak sun hours directly impact the number of solar panels you need. If you live in a place that receives a lot of sunlight, such as Arizona, a smaller solar power array might fulfill all your needs. You would need a bigger system to achieve the same amount of energy production if you live in an area with less available sunlight, such as Massachusetts.

For our example, we will use Arizona, which receives an average of 7.42 peak sun hours per day.

3. Plug Consumption and Peak Sun Hours into the Formula

1,200 kWh / (7.42 × 30) = 5.4 kW Solar System

Note: We multiplied Arizona's average peak sun hours by 30 to get a ballpark estimate of peak sun hours that the state gets per month.

4. Convert kW to Total Watts

Since 1 kW equals 1,000 watts, we will multiply 5.4 kW by 1,000:

5.4 × 1,000 = 5,400 Watts

5. Determine the Generation Capacity of Your Potential Solar Panels

Different solar panel designs have different power generation capacities, according to expected solar panel output efficiency. Some companies sell designs at 320 watts in the standard solar panel size, others at 280 watts, or even 250 watts. Some high efficiency panels can produce up to 400 watts or more per panel. Panel wattage is one factor that determines whether a given system requires more panels or fewer panels.

We'll use 280 watts for this example, which is a good measure for most solar panels. Simply divide the total watts above by the total wattage output of your solar panel design to determine how many solar panels you will need:

5,400 / 280 = 19.3 solar panels needed to cover total electricity usage

In this example, the homeowner would need a system with around 20 solar panels to provide all of their energy needs. Solar installers typically factor in many additional variables when sizing a solar power system; however, this number provides an appropriate baseline when thinking about your own solar power plans.

When you work with Palmetto to design your perfect solar power system, we take care of the entire process, including the calculations required for the solar panel type, panel wattage, roof space, production ratio, energy usage vs. energy bills, and estimated energy output, to find out how many solar panels you need. We provide a comprehensive and accurate assessment, so you don't have to worry about the details of too many or too few panels.

The Number of Solar Panels You Need Depends on You

You now have a rough idea of the solar system size you need to power your home. Great! There are a few more details to set yourself up for success, including your budget and solar goals. We recommend you engage a solar panel professional to address the following questions about solar array size.

How many solar panels do I need for my roof design?

The design of your roof determines how the solar panels will be installed, and how much sunlight they will get. If your roof is well-angled and features enough usable roof space, it can accommodate more panels and a large solar panel system. If there is only a small available area, you may be forced to install a reduced system with costlier panels to generate the solar power you want.

The direction your roof faces also impacts the amount of sunlight your solar panels will receive. Better exposure (typically south-facing) requires fewer solar panels. However, if your roof faces in a direction that receives less sunlight, your solar company might have to adjust the orientation of your system to provide you sufficient electricity. That's why it is important to consult with a professional solar installation company like Palmetto when assessing how many panels you need and installing a solar system.

How many solar panels do I need for home appliances?

Do you know how much power you're using each month? Just knowing the monthly energy consumption on your power bill isn't always enough to help you make the right decision. You need to look around your house to learn where and when you use electricity, especially for your appliances.

For example, you may notice higher-than-average consumption when using a washing machine or playing video games during the daytime. Understanding how your appliances use electricity gives you insights into when you are likely to need more electricity.

To track the energy usage for individual appliances, you can install an electricity usage monitor or smart plug between the outlet and the appliance. Leave the usage monitor on for a week and use that data to calculate the total number of kilowatt-hours per day that your appliances use.

Home appliances with the highest average electricity consumption include:

  • Refrigerator
  • Heater
  • Air conditioner
  • Dehumidifier
  • Dishwasher
  • Electric oven
  • Washing machine
  • Dryer
  • PCs (especially gaming computers)

Once you know the energy consumption of your appliances and when they’re used, you can figure out the size of the solar panel system you need to install to generate sufficient electricity for your energy usage.

How many solar panels do I need if I have a lot of trees?

The beautiful trees around your home can impact how much solar energy your solar panels generate. Even if your area enjoys a high amount of peak sunlight hours, tree coverage may diminish your total energy generation.

You may have to trim trees so your solar panels can generate as much electricity as you need, which is a more cost-effective solution than adding more solar panels. If you don’t trim them, your roof might be shaded during certain times of the day and that would require a larger system to compensate for the decreased production.

Sometimes you can’t trim trees to improve your energy production, such as tall trees on the edge of a neighbor’s property. In this case, your system design will have to account for this decrease in morning or afternoon production.

How many solar panels do I need for my future energy plans?

Is your electricity consumption rate likely to increase in the coming years? When assessing your solar panel requirements, you need to think about any big changes in your electricity usage that might develop. This includes purchasing an electric car, larger HVAC system, or hot tub, leveraging net metering, and anything else that affects the size of your electricity bill.

In short, the greater your future energy needs, the more solar panels you may want to install now to account for that future consumption.

Key Solar Panel Installation Takeaways

There’s a lot to consider before installing solar panels on your home, however the factors we discussed will help you estimate the size of the system you need. Keep in mind this is simply an estimate of how much solar power you need—use it as a guide, not as the final figure.

Once you have your system size estimate, the best way forward is to speak to Palmetto. Our experts will assess your needs, situation, and budget to help you settle on the number of solar panels that will work for you.

We’ll help you figure out the number of solar panels that are enough for your home, answer any questions you might have (including about options to profit from excess energy and advanced solar batteries), and calculate how much you can save by going solar. Get in touch today to begin a conversation about achieving your home solar system dreams.

See what solar can do for you:

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About the AuthorCory O'Brien HeadshotCory O'BrienSenior Director - Growth Marketing

Cory brings over 8 years of solar expertise to Palmetto, and enjoys sharing that knowledge with others looking to improve their carbon footprint. A dog lover residing in Asheville, NC with his wife, Cory graduated from UCSB. If you run into him, ask him about the company he founded to rate and review beer!

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