How Much Energy Does a Solar Panel Produce?

There’s a short answer and a long answer to the question “How much energy does a solar panel produce?”

The short answer is, it depends.

The long answer is it depends on everything from the panel’s size, efficiency, age, location, orientation, and tilt, to the weather conditions and the intensity of the sunlight at the moment you want to know. Understanding these factors will give you an answer to your question and help you maximize the electricity production of your solar panel system.

How to Calculate the Energy Output of a Solar Panel

Most solar panels are sorted by their energy output. If you see a solar panel listed as 400 watts, you know its output under ideal conditions is going to be 400 watts. 

If it is math that you are after, you can use the following formula to calculate the potential energy output of a solar panel (or set of solar panels) at any given moment in time: Power (W) = Area (m2) x Efficiency (%) x Solar Irradiance (W/m2). 

Let’s break it down piece by piece, and then illustrate a few examples. 

• Power: Electricity is measured in watts, whether produced by your solar panels or consumed by your dishwasher. 1,000 watts is equal to 1 kilowatt, and electricity use over time is measured in watt-hours or kilowatt-hours. 
• Area: Measured in square meters, area refers to the amount of space occupied by photovoltaic (PV) cells. In the US, residential solar panels measure about 17.5 square feet on average, which is equivalent to 1.62 square meters (m2). 
• Efficiency: The efficiency of a solar panel determines how well it can convert sunlight into usable electricity. Today’s top solar panels generally have efficiency ratings near or above 20% and slowly lose efficiency over time.
• Solar Irradiance: Solar irradiance refers to the intensity of the sunlight shining on solar panels. On average, rooftop panels receive solar irradiance of 1000 watts, or 1 kilowatt, per square meter (1000W/m2 or 1 kWh/m2) during peak sun hours. Although panels still work during the morning and early evening, the majority of solar output occurs during these peak sun hours as illustrated in the chart below. 

So while a solar panel’s output is measured in watts, the electricity it produces is measured in watts-hours. Calculating watt-hours is easy, as a simple measurement of energy output over time. If your solar panel produces 400W of energy for an hour, this would create 400 watt-hours (Wh) or 0.4 kilowatt-hours (kWh) of solar electricity.

Okay, now the fun part: a look at how much energy the same solar panel could produce in a few scenarios.

• Clear day vs overcast day: At noon on a cloudless day, a 1.6 square meter solar panel with a 20% efficiency rating would receive approximately 1,000 W/m2 in the US, and therefore produce 320W (1.6 x 0.2 x 1,000). On a cloudy day at the same time, there may only be half of the solar irradiance available, reducing power output to 160W (1.6 x 0.2 x 500).
• Summer vs winter: While temperature changes have slight effects on power output, solar panels can theoretically produce the same amount of electricity in the winter or summer when exposed to direct sunlight. Instead, the biggest seasonal difference in solar potential lies in peak sun hours per day. For example, in Austin, Texas, peak sun hours per day can range from over six in the summer to under three in the winter. Here, the solar panel from above could generate over two kWh per day in the summer (320W x 6.5 hours) or less than one kWh (320W x 3 hours) in the winter.
• Location: Location is one of the most important factors in determining how much electricity can be generated in a year. Solar irradiance per day is greatest in the Southwest and lowest near the Canadian border, according to the National Renewable Energy Laboratory. In our example, the same 320W solar panel would theoretically produce 584 kWh annually in Florida (320W x 5h x 365 days) or 467 kWh in Chicago (320W x 4 hours x 365 days).

For a more detailed and interactive way to see how much energy a solar panel can produce on your property, visit NREL’s PVWatts Calculator.

How to Maximize the Energy Output of a Solar Panel

Solar panels deliver value with every watt-hour they generate. By maximizing the energy output of your solar panels, you can further reduce utility bills, shorten your payback period, and increase your return on investment. To maximize your solar power production, we recommend the following.

1. Install premium equipment. Choose the right solar panel quality and quantity for your home’s energy needs and roof space. In the US, the average home solar energy system is about 7.15 kW in capacity, or approximately 20 solar panels rated at 350W each.  
2. Utilize your usable installation space. On rooftop systems, solar panels should be placed flush against sloped, south-facing roofs or on any face that receives direct sunlight most of the day. For ground-mounted solar panels or homes with flat roofs, you can maximize your solar panel energy output by tilting panels towards the sun at the optimal angle for year-round production. 
3. Avoid power loss from shade. Shade can dramatically affect solar panel performance. As such, installations should be placed out of any shade from trees, neighboring buildings, chimneys, or other obstructions. 
4. Clean panels regularly. As solar panels require direct sunlight to produce electricity, any dust, dirt, or debris covering an installation can seriously impact energy production. Homeowners can clean solar panels once or twice per year to maintain maximum energy efficiency, though rain and snow do a decent job of cleaning panels, too.
5. Keep an eye on things. Tracking solar power output on a smart meter or solar monitoring app can help you discover interruptions in ordinary production from a malfunctioning panel or inverter. Noticing immediate changes in energy production can help you quickly order repairs and keep things running smoothly. Some monitoring services, like Palmetto Protect, will proactively monitor the system for you.
6. Integrate other energy upgrades. You can use your solar power to its fullest potential with additional upgrades for your home’s energy management and efficiency like integrated battery storage, smart thermostats, energy-efficient appliances, and interconnected EV chargers. 

Lengthy warranties and performance guarantees can ensure that, if something does go wrong, you’re not on the hook for underperformance or expensive repairs. Palmetto customers with a LightReach Energy Plan get monitoring and maintenance throughout the life of their plans.

Final Thoughts

Estimating how much energy a solar panel or set of solar panels will produce can help determine whether or not an installation will be worth it for your home. A solar panel installation that delivers long term savings can take many different forms, but its design and how you monitor and maintain it can boost the amount of energy it produces.

If you’re interested in exploring how solar panels might work at your home, contact Palmetto today or explore your savings with Palmetto’s solar savings calculator.

About the AuthorBrian ChurchWriter

Brian is a writer, NABCEP PV associate and outdoor enthusiast living in Denver, Colorado. As a freelancer, Brian has written hundreds of articles to help individuals, businesses and our planet benefit from solar power and sustainable energy systems.