power output of a solar panel

How much energy does a solar panel actually produce? Electricity output explained

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Power output or wattage is an important factor to consider when comparing solar panel options. You may hear your solar installer say, “it’s a 255 Watt panel” or “the panel I am recommending is has a wattage of 300.” Or, when you are reading a quote from a solar installer, you might see numbers like 245W, 300W, or 345W next to the name of the panel. They are all referring to a solar panel’s wattage, capacity and power output.

How much energy does a solar panel produce?

For the sake of example, if you are getting 5 hours of direct sunlight per day in a sunny state like California you can calculate your solar panel output this way: 5 hours x 290 watts (an example wattage of a premium solar panel) = 1,450 watts-hours, or roughly 1.5 kilowatt-hours (kwh). Thus, the output for each solar panel in your array would produce around 500-550 kWh of energy per year.

All solar panels are rated by the amount of DC (direct current) power they produce under standard test conditions. Solar panel output is expressed in units of watts (W) and represents the panel’s theoretical power production under ideal sunlight and temperature conditions. Most home solar panels on the market today have power output ratings ranging from 250 to 400 watts, with higher power ratings generally considered preferable to lower power ratings. Pricing in solar is typically measured in dollars per watt ($/W), and the total wattage of your solar panels plays a significant part in the overall cost of your solar system.

What can you power with a single solar panel?

In the example above, the solar panel is producing 1.5 kWh per day, which ends up being about 45 kWh per month. That’s enough energy to power some small appliances without too much issue, but if you want to cover the energy used by your property’s climate control systems or large cooking appliances, you’ll need more solar panels.

solar panel output

Why does solar panel output matter? How to calculate panel wattage

Power output is an important metric for your home or commercial solar panel system. When you buy or install a solar photovoltaic (PV) energy system, the price you pay is typically based on the total power output of the solar panels in the system (expressed in watts or kilowatts).

Solar panel wattage represents a solar panel’s theoretical power production under ideal sunlight and temperature conditions. Wattage is calculated by multiplying volts x amps where volts represents the amount of force of the electricity and amperes (amps) refers to the aggregate amount of energy used. The financial savings you derive from the solar system is a result of the electric energy that it generates over time (expressed in kilowatt-hours).

Size vs. quantity: typical solar panel ratings and capacity

Power output on its own is not a complete indicator of a panel’s quality and performance characteristics. For some panels, their high power output rating is due to their larger physical size rather than their higher efficiency or technological superiority.

For example, if two solar panels both have 15 percent efficiency ratings, but one has a power output rating of 250 watts and the other is rated at 300 watts, it means that the 300-watt panel is about 20 percent physically larger than the 250-watt panel. That’s why EnergySage and other industry experts view panel efficiency as being a more indicative criterion of solar panel performance strength than solar capacity alone.

In practical terms, a solar panel system with a total rated capacity of 5kW (kilowatts) could be made up of either 20 250-Watt panels or 16 300-Watt panels. Both systems will generate the same amount of power in the same geographic location. Though a 5kW system may produce 6,000 kilowatt-hours (kWh) of electricity every year in Boston, that same system will produce 8,000 kWh every year in Los Angeles because of the amount of sun each location gets each year. (Read our blog on how electricity production and electricity prices you pay to your utility impacts your savings.)

The electricity generated by a solar PV system is governed by its rated power output, but it’s also dependent on other factors such as panel efficiency and temperature sensitivity, as well as the degree of shading that the system experiences and the tilt angle and azimuth of the roof on which it’s installed. As a general rule of thumb, it makes prudent financial sense to install a solar system with as much power output as you can afford (or that your roof will accommodate). That will ensure you maximize your savings and speed up the payback period of your solar energy system.

Find out more about average prices for solar across the country for 3kW,4kW5kW6kW, 7kW8 kW and 10kW solar systems. The EnergySage Solar Marketplace makes it easy for you to compare your savings from solar panels with various power output ratings.

solar panel output

How many watts of energy does a solar panel produce?

The two graphics below present different views of power output from the leading manufacturers who supply solar panels to the U.S. market. Because panel manufacturers often produce more than one line of solar panel models, the power output of most company has a significant range. The image below lists the minimum, maximum, and average power outputs of the solar panels within each manufacturer’s portfolio.

Electricity output (in Watts) of solar panel manufacturers

Solar Panel Manufacturer
Minimum
Maximum
Average
Amerisolar240330285
Axitec250350287
Canadian Solar225350292
CentroSolar250320278
ET Solar255340296
Green Brilliance230300266
Hanwha Q CELLS285390324
Hyundai265375346
Kyocera260330295
LG315375346
REC Solar275380236
Silfab290380329
SunPower320435353
Trina Solar Energy260370320

Three Tips for Solar Shoppers

1. Homeowners who get multiple quotes save 10% or more

As with any big ticket purchase, shopping for a solar panel installation takes a lot of research and consideration, including a thorough review of the companies in your area. A recent report by the U.S. Department of Energy’s National Renewable Energy Laboratory (NREL) recommended that consumers compare as many solar options as possible to avoid paying inflated prices offered by the large installers in the solar industry.

To find the smaller contractors that typically offer lower prices, you’ll need to use an installer network like EnergySage. You can receive free quotes from vetted installers local to you when you register your property on our Solar Marketplace – homeowners who get 3 or more quotes can expect to save $5,000 to $10,000 on their solar panel installation.

2. The biggest installers typically don’t offer the best price

The bigger isn’t always better mantra is one of the main reasons we strongly encourage homeowners to consider all of their solar options, not just the brands large enough to pay for the most advertising. A recent report by the U.S. government found that large installers are $2,000 to $5,000 more expensive than small solar companies. If you have offers from some of the big installers in solar, make sure you compare those bids with quotes from local installers to ensure you don’t overpay for solar.

3. Comparing all your equipment options is just as important

National-scale installers don’t just offer higher prices – they also tend to have fewer solar equipment options, which can have a significant impact on your system’s electricity production. By collecting a diverse array of solar bids, you can compare costs and savings based on the different equipment packages available to you.

There are multiple variables to consider when seeking out the best solar panels on the market. While certain panels will have higher efficiency ratings than others, investing in top-of-the-line solar equipment doesn’t always result in higher savings. The only way to find the “sweet spot” for your property is to evaluate quotes with varying equipment and financing offers.

For any homeowner in the early stage of shopping for solar that would just like a ballpark estimate for an installation, try our Solar Calculator that offers upfront cost and long-term savings estimates based on your location and roof type. For those looking to get quotes from local contractors today, check out our quote comparison platform.

solar panel output

35 thoughts on “How much energy does a solar panel actually produce? Electricity output explained

  1. Steve Goldfield

    Some of my 320W LG solar panels were producing 327W today. In other words, they were producing more than their rating. I would not have thought that was physically possible.

  2. M Hrywnak

    this article does not address the size i.e. square footage of the solar panels, in other words if I have a 600 sf roof what is the total power it could produce?

  3. Kevin

    So i have 12 300 watt panels on my riof facing due south. My system has a sunnyboy 6.5kw inverter which shows output. I live in northern California. In mid day i expect 3600 watts to be produced but have not seen over 2700. My installer says it is because it is so hot outside. Seem fishy to you?

  4. Stephane Menand

    Kevin,

    While 3600 to 2700 is a lot it is not impossible if your panels are really hot which is most likely at Solar noon at your location in the summer. unfortunately most solar panels voltage will drop considerably when they get too hot. The watts rating of your solar panels is calculated from STC 1000/square meter and at 25 Celsius ambient temp. Each time they are a degree Celsius over the 25 the voltage will drop by a certain pourcentage.your panels will often be running at the high of the day at 20 to 30 degrees above the 25 c which means their voltage could drop by 5 to 10 percent easily and therefore the watts will go down accordingly.
    Best for you is to get someone to check your panels temperature with a solar gun and take also the irradiance at the same time and see what the expected production should be at that time and comparing to what your inverter is showing at the same time. Remember that your inverter shows AC and that therefore there will be also a small loss between The DC side of your solar panels and of your AC side of the inverter.
    I hope the explanation helps you understand where the discrepancy may be coming from. I wish your installer would have explained to you what to expect and that he would do a test as I explained so you know if the descrapency is justified or not.
    Good luck!

    Stephane

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