How Many Solar Panels Do You Need: Panel Size and Output Factors (2023)

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:

  1. Your average energy requirements

  2. Your current energy use in watts

  3. The climate and amount of sunlight in your area

  4. The efficiency of the solar panels you’re considering

  5. 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.

How Many Solar Panels Do You Need: Panel Size and Output Factors (1)

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 Many Solar Panels Do You Need: Panel Size and Output Factors (2)

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.

Related posts

  • Solar 101: How Does Solar Energy Work?

  • How a Southern California Family Went Solar to Save on Summer Electric Bills

  • How Home Solar Panels are Installed

Interested in high-efficiency solar panels for your home? Contact SunPower for more information.


How Many Solar Panels Do You Need: Panel Size and Output Factors? ›

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).

What is the standard solar panel size and output? ›

Usually, 60-cell solar panels are about 5.4 feet tall by 3.25 feet wide and have an output of about 270 to 300 watts. On the other hand, 72-cell solar panels are larger because they have an extra row of cells, and their average output is somewhere between 350 to 400 watts.

Does the size of a solar panel affect power output? ›

For example, a small solar panel may be highly efficient but not have a high wattage rating because of its small size. Likewise, a relatively large solar panel with a low efficiency will not necessarily have a high wattage.

What size solar panel setup do I need? ›

The rule of thumb for working out solar system size is to divide your average daily electricity usage by 3.5.

What is the formula for calculating solar panels? ›

Suppose you live in an area that receives 4 hours of peak sunlight, and your panel has a 200-watt rating. In this case, the solar panel output will be: Daily watt hours = 4 × 200 × 0.85 = 680Wh. That means one solar panel with a 200-watt capacity can produce around 680 Wh, depending on its efficiency.

How many solar panels do I need for a 2000 sq ft home? ›

The average cost of solar panels for a 2,000 square foot home is $36,000. To achieve this goal, you'll need approximately 20 solar panels – which means that the total cost of installing solar panels on your home will be around $532 per panel.

What size is a 72 cell solar panel? ›

Standard Solar Panel Sizes

72-cell panels: 39″ x 77″ (3.25 feet x 6.42 feet)

How do I know if my solar panels are producing enough power? ›

Read Your Solar Meter

Typically, your meter will cycle through different screens. You should pay particular attention to the one that displays the total kilowatt-hours that your solar panels are generating. As long as your kilowatt-hours are increasing, your solar panels should be working fine.

Are larger solar panels more efficient? ›

Key Takeaways. The size of solar panels certainly matters, but larger solar panels are not necessarily better. In order to provide more power with less space, you want a panel with a higher power rating and a lower physical size.

Does a bigger solar panel charge faster? ›

Simply, the larger the solar panel the more electricity generated, and therefore the faster the charge or the greater the ability to charge higher capacities. This is an important practical consideration as there will always be a limited amount of day, or sunlight.

Do you need a 200 amp panel for solar? ›

Most homes need a 200-amp electric panel as a minimum. A new solar-ready panel will have enough circuits to accommodate your new solar panel system. It will also have space for clearly marked ratings and locations of all the components that the solar technicians installed.

Is 5kW enough to run a house? ›

Yes, a 5kw solar system can provide enough power for a small home or apartment. It will not be able to run a larger home or all of the appliances in a home. However, it's important to note that a 5kW solar system may not be sufficient to power a larger home or to run all of the appliances in a home.

What is the average number of solar panels needed? ›

The average household in the U.S. consumes 886 kilowatt-hours (kWh) of electricity per month, or 10,632 kWh of electricity per year. To generate that much electricity, the average U.S. household would need about 15 to 20 solar panels. However, this number varies by state and individual needs.

What is the average output per day of a solar panel? ›

Multiply 5 hours of sunlight x 290 watts from a solar panel = 1,450 watts or roughly 1.5 kilowatt hours per day. That's about 500-550 kilowatt hours of energy per year from each panel on your roof.

Is there a solar calculator? ›

EcoWatch's solar calculator is one of the best tools to help you determine your potential solar energy savings for the new year.

How many solar panels do I need for 500 kWh per month? ›

How many solar panels do you need based on your kWh usage?
Monthly kWh UsageTypical System Size# of panels (315W)
5003.58 kW12
6004.30 kW14
7005.02 kW16
8005.73 kW19
15 more rows
Nov 26, 2019

What is the normal size of a solar panel? ›

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.

What is normal solar panel output? ›

Most residential solar panels have power output ratings from 250 to 400 watts, depending on panel size and how well they convert sunlight into energy. While higher power ratings are considered preferable, power output is not the sole factor in judging a solar panel's performance.

Is there a standard size for solar panels? ›

The standard solar panel size, the 60-cell is structured as a 6×10 grid and measures 3.25 feet by 5.5 feet. The average 72-cell solar panel size measures 3.25 feet by 6.42 feet and is laid out as a 6 x 12 grid, making them almost a foot taller than the 60-cell standard size panels.

What is the typical output of a 100 watt solar panel? ›

The 100-watt solar panel typically produces 300-600 watt-hours per day, depending upon the peak sun hours you receive.

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