How much energy does a solar panel produce?


How much energy does a solar panel produce?
A typical single solar panel will produce about 2 kWh per day. But what exactly does that mean?

While many factors 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 kilowatt-hours (kWh) per day, saving 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 $130 a month (or more!).

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

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Key takeaways

  • Most residential solar panels today have a power output rating of between 370 watts and 400 watts.
  • The average-sized solar panel will produce between 1.5 kilowatt-hours and 2.4 kWh of electricity per day.
  • One solar panel generates enough electricity to power small appliances like a TV, lights, or device chargers.
  • How much energy a solar panel produces depends on how much sunlight the panel gets, the panel’s construction, your roof’s characteristics, and even how old the panel is.
  • 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.

How much electricity does a solar panel generate?

The average solar panel is able to output between 370 and 400 watts of power. This works out to a single solar panel producing about 2 kilowatt-hours (kWh) of electricity per day. That’s enough electricity to watch your TV nonstop for almost a full 24 hours.

The following table outlines how much electricity a 400-watt solar panel would produce under ideal conditions over the course of a day, a week, and a month:

Time Electricity production of 400-watt solar panel*
1 day 2 kWh
1 week 14 kWh
1 month 60 kWh
1 year 730 kWh

*Assumes 5 peak sun hours

How many solar panels do I need to power my house?

Let’s be honest, no one is installing just one solar panel on their roof. As mentioned above, one solar panel will produce roughly 2 kWh daily. On the other hand, the average U.S. home uses about 29 kWh of electricity daily. So, you’ll need a lot more than just one panel.

In fact, you’ll probably need at least 15 solar panels on your roof to generate enough electricity to cover your daily energy usage. That works out to about 6,000 watts of solar, or 6 kilowatts (kW). A 6 kW system will produce about 10,950 kWh per year. That’s enough electricity to cover the average household’s electricity usage and potentially eliminate a $135 electricity bill.

The actual number of solar panels you need will largely depend on how much energy you use throughout the year. But it will also depend on your panels' environment and the panels themselves.

4 factors that affect the amount of electricity that solar panels produce

We want to be totally honest with you, most of the time, solar panels won’t produce the maximum amount of energy possible. Solar panel specifications, like power output ratings, are determined by testing the panels in a laboratory under Standard Test Conditions.

Your roof isn’t exactly a lab, and the conditions it’s under aren’t always going to be ideal for your solar panels. There are a number of things that will impact how much energy your solar panel is generating.

1. Amount of sunlight

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

This means you’ll want to install solar panels on an unshaded portion of your roof. You don’t want overhanging tree branches or your chimney casting shadows on your panels. Even dust and debris can cause your panels’ production to drop, so it’s important to clean your solar panels once or twice a year.

It’s more than just if your panels are shaded or not. It also has to do with if where you live naturally gets a lot of sunlight. Scientists use “peak sun hours” to compare how much sunlight different places get. Solar panels will be able to generate more electricity in places that get more peak sun hours.

The following table lays out how much energy a 400-watt panel could produce in states that receive different amounts of sunlight, assuming all other conditions are the same:

State Number of peak sun hours Daily electricity production
Arizona 7.5 3.0 kWh
Alaska 2.5 1.0 kWh
California 6 2.4 kWh
New Jersey 4 1.6 kWh

You can hear more about how weather conditions impact solar panel production in this video from SolarReviews founder, Andy Sendy:

2. Panel characteristics

The panel itself also affects how much energy it can produce. Solar panels are made up of solar cells, which are what actually turn sunlight into electricity. Today, most solar panels use monocrystalline solar cells, AKA the most efficient silicon solar cell made today. If you used a polycrystalline solar panel, it wouldn’t be able to generate as much electricity as its monocrystalline counterpart.

It’s not just about the material the solar cells are made out of – how much electricity a panel produces is also impacted by how many cells there are and how those cells are shaped! Solar panels typically come in two sizes: 60-cell solar panels for homes and 72-cell panels for larger commercial installations.

72-cell panels have more solar cells, so they’re able to generate more electricity, but they’re too large to use on many residential roofs. However, a lot of solar panel manufacturers today are starting to make 66-cell solar panels that are still practical for home solar, but the extra six cells mean the panels can produce more energy!

Manufacturers are also making more half-cut solar panels, where the solar cells are cut in half with a laser before being put into the panel. This increases the efficiency of the panel so it can generate more electricity. Half-cut panels are also wired differently than traditional panels, so shading has less of an impact on how much energy is generated.

Bifacial solar panels: Bifacial solar panels are able to generate electricity from light that hits both the front and the back of the panel. When sunlight hits the ground and bounces back up, bifacial panels can capture that reflected light and use it to make more electricity. These aren’t particularly useful for homeowners with rooftop solar, but they can be a great option for ground-mounted systems.

3. Your roof

The truth is, not all roofs are good for solar. The characteristics of your roof are a major player in how much energy solar panels can produce for your home.

The number one thing you need to consider is the direction of your roof. The best direction for solar panels to face is south, so you’ll want to have a south-facing roof for maximum energy production. This doesn’t mean you can’t install solar panels if your roof faces a different direction. The panels will just generate less electricity because they get less sunlight.

The following table outlines how much electricity a solar panel will generate facing different directions if all other factors are the same:

Solar panel direction Estimated output*
South 2 kWh
East 1.7 kWh
West 1.7 kWh
North 1.4 kWh

*Assumes 400-watt solar panel and 5 peak sun hours

4. The panel’s age

The panel’s age is often forgotten, but it’s important to remember that your solar panels won’t produce the same amount of energy for their whole life. As solar panels age, they lose a bit of their ability to generate power. You can think of it as any other electronic you have - your laptop probably doesn’t work as well as it did the day you bought it.

Solar panels, on average, degrade at a rate of about 0.5% per year. So, by the end of a panel’s typical 25-year warranty period, they usually operate at about 85% of what it was initially. Don’t worry – your solar panels will still generate enough electricity to help lower your utility bills.

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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 - figuring out how much power solar panels will produce for your home.

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:

All you need to do is multiply the wattage of your panel by the number of daily peak sun hours. A homeowner in Florida who installs a 400-watt solar panel can expect about four peak sun hours in a day. That means this panel would produce 1,600 watt-hours of electricity per day. Electricity is usually measured in kilowatt-hours, so you simply divide your 1,600 watt-hours by 1,000 to get 1.6 kilowatt-hours.

400 watts x 4 peak sun hours = 1,600 watt-hours per day 1,600 watt-hours /1,000 = 1.6 kWh per day 1.6 kWh x 30 days = 48 kWh per month 1.3 kWh x 365 days = 584 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 the factors mentioned earlier. Use our solar panel calculator to get a more accurate view of how much electricity you can expect solar to produce on your roof.

Solar panel model Power rating Estimated daily power production*
SunPower M-Series 440 W 2.20 kWh
REC Solar Alpha Pure 430 W 2.15 kWh
Candian Solar HiKu6 420 W 2.10 kWh
Qcells Q.PEAK DUO BLK ML-G10+ 410 W 2.05 kWh
Jinko Eagle 66TR G4 400 W 2.00 kWh

*Estimated production of a single panel assuming 5 peak sun hours at STC.

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, but you’ll need fewer panels to meet your energy needs.

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 discussed earlier could save the average American homeowner around $130 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 depends on many factors. The easiest way to determine 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, but you can also choose to get in contact with vetted local solar installers to start getting real solar quotes for your specific home.

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 - Author of Solar Reviews

Catherine Lane

Written Content Manager

Catherine is the Written Content Manager at SolarReviews. She has been researching and writing about the residential solar industry for four years. Her work has appeared in Solar Today Magazine and Solar Builder Magazine, and has been cited by publications like Forbes and Bloomberg.

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