How Much Energy Does a Solar Panel Produce?

When considering solar panels for your home, you probably wondered: How much electricity will they produce? Solar panels are rated by their output in watts, but their real-world performance depends on more than that number alone.

This guide breaks down the science of solar output, explaining the key factors that influence production, such as the panel's efficiency, your location's sunlight intensity, and seasonality. Understanding this calculation is essential for designing a system that matches your home's energy needs and maximizes your financial return for the long life of your panels.

How much power does a solar panel produce?

Most home 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 will be 400 watts.

Power output depends on the solar panel specifications, like efficiency, as well as the panel’s location, orientation, and angle. The current season, weather, and the overall climate where you live also play a role. Designing a system for your specific situation can increase the production and efficiency of your home solar panels.

The solar company designing and installing your solar panel system often seeks to match this output to your yearly consumption as closely as possible.

How to calculate the energy output of a solar panel

If you want to do the math, 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: Solar panel efficiency is how well a panel converts 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 and is measured in peak sun hours. One peak sun hour is the amount of sunlight equal to 1,000 watts of solar irradiance on one square meter over an hour. The more peak sun hours a location receives, the more electricity solar panels will produce.

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

Okay, now the fun part. Let’s look at how much energy the same solar panel produces 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 be half 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 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 reduce electric 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 18 solar panels rated at 400W 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 reduce their 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. Track solar performance. 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. You can find smart and energy-efficient products, plus ways to track your home’s energy usage and spend less by saving energy in the new Palmetto app.

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

Learn how much energy solar panels can produce at your home

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 proper design, monitoring, and maintenance can increase its production.

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

Frequently asked questions

How much energy does a solar panel produce per day?

You can calculate how many watt-hours of electricity a solar panel produces in a day by multiplying the panel’s wattage by the peak sunlight hours. For example, a 400W solar panel receiving 5.5 peak sun hours would produce 2,200 watt-hours, or 2.2 kilowatt-hours, of electricity.

Can solar panels power a house on their own?

Yes, it’s possible to have solar panels power your home on their own, though you’ll need batteries to get you through the night and bad weather. Most homes with solar panels are connected to the grid for when their demand for electricity exceeds their solar panel production.

Do you need a battery if you go solar?

You do not need a battery to go solar. Without a solar battery, the excess power your system generates will go into the utility company’s electricity grid. This can earn net metering credits on your electricity bills, at a value determined by your utility, locality, or state. With a battery, you can store excess solar electricity and use it to avoid buying utility-supplied electricity later.