How much energy do solar panels produce per square foot

While there are many factors that affect the amount of energy a solar panel can produce, you can expect a typical single solar panel in the United States to generate about 2 kWh per day, which saves an average of $0.36 on electricity costs per day. 

Now, $0.36 doesn’t seem like a lot, but that’s just the energy savings for one panel over the course of one day. Installing a whole solar panel system, on the other hand, would save you more like $132 a month (or more!). 

What exactly determines how much electricity a solar panel will produce, and how can you figure out the amount of one solar panel’s generation? Let’s find out.

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Key takeaways

• A 370-watt solar panel will produce between 1.4 kWh and 1.9 kWh of electricity on average, per day, in the United States - which is enough to run a few small electrical loads like a TV, lights, and device chargers.
• There are two main things that influence solar panel production: the physical characteristics of the solar panel and how much sunlight the panel has access to.
• The SunPower A Series panel has a power rating of 425 W, meaning it can produce more electricity than any other residential solar panel on the market.
• Installing a whole solar panel system allows you to power your home with renewable energy, decrease reliance on your utility, and most importantly, lower your electric bill.

What affects the amount of electricity that solar panels can produce? 

There are several factors that affect the amount of power that will be produced by a solar panel, but there are two categories that have the most influence: 

• Characteristics of the solar panel itself
• How much sunlight the solar panel has access to

Panel characteristics 

When it comes to power production, the most important thing to look at is the wattage, or power rating, of the panel. The wattage represents the amount of power that a panel will produce under a specific set of lab conditions, called Standard Test Conditions (STC). 

Most residential solar panels used today have a power rating of somewhere between 300 and 370 watts in size. The higher the wattage of a panel, the more electricity it can produce. 

The wattage of a panel has to do with the way the panel is constructed. The type of solar cells used, for example, influences the wattage of a panel. This is why most solar panels today use something called monocrystalline solar cells, because they’re able to generate more electricity than older solar cell technologies (namely polycrystalline solar cells). 

The number of solar cells within a panel will also impact how much energy it can produce. Typically, solar panels will either have 60 cells or 72 cells. 72-cell panels produce more electricity simply because there are more solar cells, however, they are much larger in size so they’re rarely used for residential solar. 

Amount of sunlight 

The amount of sunlight that hits a solar panel is another big factor in how much electricity it will generate. The more sunlight available to the panel, the more electricity it can produce. 

When tested in a lab, solar panels are exposed to 1,000 watts of sunlight per meter squared over an hour. This is what is known as a “peak sun hour”, and scientists out there have figured out the amount of daily peak sun hours that various places on earth receive. Solar panels are able to produce more electricity in places with a higher number of peak sun hours. 

The following table shows how much energy a 370-watt panel could produce in different states that receive different amounts of sunlight, assuming all other conditions are the same: 

As you can see, a solar panel can produce double the amount of electricity in sunny states like Arizona and California than it can in a not-so-sunny state like Alaska. 

You can still install solar in Alaska - this just means you would need to install three solar panels in Alaska to produce the same amount of electricity that one panel produced in Arizona. 

Other factors 

There are a bunch of other things that go into how much electricity a solar panel will produce. Take panel temperature for example: as a solar panel gets hotter, it actually produces less electricity. Crazy, right? You can read more about how temperature affects solar production here.

If the panel is covered in any way, whether by the shade from a tree or by dust that settles on the panel’s surface, it will produce less electricity. 

Even the slope and the direction of your roof will change the amount of solar electricity generated. In general, south-facing roofs are able to produce more electricity simply because of how the sun travels in the sky. You can learn more about whether your specific roof is good for solar here.

How to determine how much electricity a solar panel can produce 

So, now that we’ve covered what impacts a solar panel’s ability to produce electricity, we can get into the good stuff, aka how much electricity a panel produces. 

We’ve already established that there are a number of factors that are going to impact how your solar panels generate electricity. So for the sake of simplicity, we’re only going to take a couple of things into account for the below example, including: 

• The wattage of the panel
• The peak sun hours in your area - which you can find here

All you need to do is multiply the wattage of your panel by the number of daily peak sun hours for your area. 

A homeowner in New York who installs a 370-watt solar panel can expect about 3.5 peak sun hours in a day. That means this panel would produce 1,295 watt-hours of electricity per day (typically, you’ll see electricity measured in kilowatt-hours, so you simply divide 1,295 watt-hours by 1,000, to get 1.3 kWh per day):

370 watts x 3.5 peak sun hours = 1,295 Watt-hours per day

1,295 watt-hours /1,000 = 1.3 kWh per day

If you wanted to know how much that panel would produce in a month, multiply 1.3 kWh by 30 days:

1.3 kWh x 30 days = 39 kWh per month

What about for a year? It’s easy - just take that 1.3 kWh and multiply it by 365 days:

1.3 kWh x 365 days = 475 kWh per year

Bear in mind, this is a really simplified way of calculating how much electricity a solar panel produces. The actual amount will fluctuate day by day, even hour by hour, based on all of the factors we’ve mentioned earlier. To get a more accurate view of how much electricity you can expect solar to produce on your roof, use our solar panel calculator. 

Which solar panels can produce the most electricity?

Like we said before, higher wattage solar panels can produce more electricity. The following table lists out some popular high-wattage solar panels that will be able to produce the most electricity for you:

*Estimated production of a single panel assuming 5 peak sun hours, 25*C cell temperature, and 1.5 air mass. 

Keep in mind, high-wattage panels tend to come with high price tags, too. This means you may have to pay more upfront for your system. You can still get the same overall system production by installing a greater number of lower-wattage panels, so long as you have the roof space. 

Should you install high-efficiency panels to produce more electricity? 

If you’ve ever looked up “How much energy can a solar panel produce” you’ve probably come across solar panel efficiency somewhere. Here’s the deal - it’s way more important to look at a panel’s wattage than it is to look at its efficiency rating. 

Why? Because the panel’s efficiency is taken into account when the power rating is calculated. You see, the power rating of the panel serves as the cap of how much electricity the panel can produce (give or take a few watts). 

So, if Panel A is 370 watts with a 19% efficiency rating, and Panel B is 360 watts with a 21% efficiency rating, it doesn't matter that Panel B has a higher efficiency rating - it will only produce 360 watts. Panel A, despite having a lower efficiency, will be able to produce more. 

You can read more about the importance of solar panel efficiency (or lack thereof) when choosing solar panels here. 

How much electricity can an entire solar panel system generate? 

Now we know how to figure out how much electricity one panel can generate, but let’s be real, no one is installing just one solar panel on their roof. One solar panel could run a few lights, charge your phone, and keep your TV on, but if you’re really looking to cover your energy costs, one panel just won’t cut it. 

A typical solar panel system in the U.S. is around 6 kW in size, or between 16 and 18 solar panels, depending on their wattage. A 6 kW system will generate somewhere between 720 kWh to 900 kWh per month (for reference, the average American household uses about 893 kWh of electricity monthly).

A 6 kW solar system won’t work for everyone though, because every household uses electricity differently! You can check out our step-by-step guide on how to figure out how many solar panels you need, or you can watch this video from SolarReviews’ in-house solar expert Will White:

Power your whole home with solar to save money 

Now you know how much solar electricity you can expect one solar panel to produce, and how much a whole system can, too. 

But the best part is that installing solar does way more than just let you power your home with renewable energy - it helps you save money. By using the electricity generated by solar panels on your roof, you don’t have to take electricity from your utility, which means they don’t have to charge you. 

Most of the time, you can install enough solar panels to cover all of your electricity costs. In fact, that 6 kW solar system we talked about earlier could save the average American homeowner between $90 and $100 a month! 

But of course, this is just an estimate. Just like with how much electricity a panel produces, how much solar panels can save you is dependent on a lot of factors. The easiest way to find out how much solar panels can save you is by using our solar panel savings calculator below. Not only will you get a free solar savings estimate, you can choose to get in contact with vetted local solar installers to start getting real solar quotes for your specific home. 

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