What Is the Output of a Solar Panel?

Solar panel output explained

Whether you’re installing solar shingles or solar panels, or any other device that harnesses sunlight to generate electricity, solar output measurements can usually be broken down into voltage, amperage and wattage ratings, which are all just units used to measure different aspects of the flow of electricity.

You can calculate how much energy your solar panels produce if you know their combined wattages and how much sunlight your property gets.

Generally, a solar panel’s potential output is rated in terms of wattage (W). That’s why you’ll see references to 300- or 400-watt solar panels as a shorthand for how powerful they are. However, if you’re looking at how much electricity a solar panel actually produces, expect to see the answer measured in kilowatt-hours (kWh). This is the same unit that’s likely used to measure your home’s energy consumption on your electricity bill.

The 250- to 400-watt solar panels on most homes produce 250- to 400 watt-hours (Wh) of electricity for each hour they’re exposed to direct sunlight. Since 1,000 watt-hours are equal to 1 kilowatt-hour, you can calculate how much energy your solar panels can produce if you know their combined wattages and how much sunlight your property gets.

» CALCULATE: How many kWh does a solar panel produce?

Below, we’ll explore voltage, amperage and wattage in greater detail.

Solar panel voltage

While a solar panel is producing electricity, its voltage refers to the rate, speed or pressure at which the electricity can be transported from the panels to the rest of your energy system.

Today, most solar panel systems have a potential output voltage of 12, 24 or 48 volts, representing the maximum speed of the electricity. Higher-voltage systems allow for more solar energy to flow to your home, battery or the electric grid at once.

Solar panel amperage

Solar panel output amperage (or amps) is a measure of electrical current used to quantify the amount of electricity “flowing” from your solar panels. Much like how river speeds are rated in cubic feet of water per second, solar panel amperage is used to measure the amount of electricity that flows out of a solar panel over time.

Solar panel wattage

Although amperage and voltage are important, wattage is the most common measurement used to predict a solar panel's output because it’s a product of the two. Solar panel electricity generation and home electricity consumption are measured in watt-hours or kilowatt-hours (1 kWh = 1,000 Wh) because these are the units used to quantify energy, which is power multiplied by time.

Basically, a solar panel’s wattage is a measure of how much energy it’s capable of producing at a given moment, while kilowatt-hours are used to measure how much energy it actually produces in an hour, day, week or year.

What influences a solar panel’s output?

It can be hard to predict a solar panel’s exact output at any moment because it’s affected by many internal and external factors. These include, but are not limited to:

Temperature

Both ambient and operating temperatures can affect solar panel output. While solar panels can work efficiently in a wide range of temperatures, most solar panels prefer cooler climates and will output slightly less energy on extremely hot days.

Panel efficiency

In addition to wattage and voltage, panels are sold with a solar efficiency rating that measures how well the solar cells can absorb sunlight and create usable electricity. Today’s best solar panels are generally rated at between 20% and 25% efficiency. Solar panels slowly become less efficient with age, though.

Sunlight intensity

While solar panels can generate marginal amounts of electricity in the early morning and late evening, solar panels work best in the late morning and early afternoon when sunlight is at its most direct and intense.

Weather and air quality

A solar panel’s output may be limited on cloudy days or while covered in snow because there’s less direct sunlight to harness. The same goes for when there’s excessive particulate matter in the air, such as smoke from a forest fire.

Solar equipment variables

Before you can use the power generated by your solar panels, the electricity will likely first need to travel through a significant amount of wiring as well as an inverter system. That means your solar panels' total potential output will be affected by the efficiency of the other hardware within your solar energy system.

» MORE: Solar energy pros and cons

How to calculate solar panel output

When looking at solar equipment ratings, think of wattage as representing how many kilowatt-hours of energy a solar panel will produce in ideal operating conditions over one full hour. For instance, if you have a 300-watt solar panel receiving full sun on a cool day, you can expect your solar panel to output 300 watt-hours (or 0.3 kilowatt-hours) of electricity for every hour it is actively producing.

Solar panels can be expected to efficiently produce electricity for three to seven hours per day, depending on your location and the time of year. For example, let’s say your 300-watt solar panel above was exposed to five peak sun hours during one day in April. With this, you could expect an average daily output of 1,500 watt-hours (300 x 5 = 1,500), or 1.5 kilowatt-hours.

To calculate the potential output of your full solar energy system, consider using the PVWatts calculator from the National Renewable Energy Laboratory (NREL) or talking to a solar installer near you. By working with a professional, you can design a solar panel system with confidence in its expected potential output and ability to reduce your energy bills.

FAQ

Bottom line

A technical understanding of solar output terms usually isn’t necessary to reap the benefits of solar power. While you can calculate your solar panels’ output if you know their wattages and how much sunlight they’re exposed to, among other factors, you may want to consider working with a solar panel professional to learn your solar panel system’s exact output.