How Much Energy Do Solar Panels Produce For Your Home?

Before installing solar panels in their home, every homeowner must first calculate how much electricity they will produce and whether this amount will be enough to meet long-term household needs. One typical solar panel generates about 2kWh per day in the US, saving $0.36 per day on electricity costs. Installing an entire system of 16 panels on average will save you $0.36 x 16 x 30 = $172.8 per month. The solar power generated by the panels will give you independence from utilities that do not have to charge you for electricity1.

How to determine how many solar panels to power a house will be optimal? The performance of installations is affected by their physical characteristics and the total amount of absorbed sunlight. The amount of electricity generated by a power system depends on its rated power output – the total energy that the panel will produce under laboratory conditions called Standard Test Conditions (STC)1.

The nominal power of a modern solar panel for residential buildings ranges from 250 to 400 watts per hour. The higher it is, the more electricity the panel can produce. A household of 4-5 people will need a 4 to 5 kW system. A typical American household needs a 10,000 kWh power grid of 20-30 panels to cover its annual electricity needs. The amount of electricity produced also depends on weather conditions, the size and condition of the roof, hours of peak sunlight exposure, and the number of panel installed.

How Do I Calculate How Much Power Does a Solar Panel Produce?

To calculate the amount of electricity that a solar panel generates per day, you need to know its size and efficiency, the number of hours of sunshine in your area. The more sunlight hits the panel, the more power it will generate. To do this, you need to know the number of hours of daily peak solar activity. This figure is different in different places on our planet. The panels generate energy when exposed to 1,000 watts of sunlight per square meter of surface for an hour under standard laboratory conditions1.

Other factors that affect the amount of energy produced by panels are their temperature, shading, and the direction and angle of the roof. The more the solar panel heats up and the more it is shaded by trees, the less energy it produces. Maximum performance is achieved when the panels are placed on the south side and the roof pitch is between 30 and 50 degrees. Since all conditions for home panels are never perfect, their efficiency is usually 20%. Higher efficiency panels (40-50%) cost more but take up less roof space2.

To find out how much energy one solar panel produces per day, you need to multiply its size (in square meters) by 1000 and then multiply the resulting figure by its efficiency indicator and by the number of hours of sunshine per day in your area. The resulting figure should be divided by 1000. 

For example, the panel has a size of 1.6 square meters. We make the calculation: 1.6 x 1000 = 1600 m2. Most panels are 20% efficient, so 1600 x 20% = 320. Let’s say your area has 4.5 hours of sunshine per day. Therefore, 320 x 4.5 = 1440: 1000 = 1.44 kWh per day. The amount of electricity generated by one solar panel per month will be 1.44 kWh x 30 = 43.2 kWh.

If the power of one panel is known, the calculations of the energy it produces will be even simpler. You just need to multiply this figure by the number of sunny hours in your area per day. For example, New York City averages 3.5 hours of sunshine per day. A homeowner living in this city installs a 370W panel. The amount of electricity it generates is 370 W x 3.5 = 1,295 watt-hours per day or 1.295 kWh1.

What Happens if My Home Produces More Electricity Than I Need?

Now we know how much electricity one panel produces. But to cover the cost of electricity, one panel is not enough. A typical solar power system in the US has 16 to 18 panels and a capacity of 6 kW, generating 720 to 900 kWh per month (the average household consumes 893 kWh of electricity monthly)3. Different households use different amounts of produced energy. If the panels generate more electricity than your household consumes, you can make money from it. Your power system may generate excess energy in such cases:

• reducing your family’s energy consumption;

• a large number of sunny days;

• installation of more panels than necessary;

• prolonged exposure of the panels to direct sunlight.

Surplus electricity returns to the grid and the local utility company buys it from you. This process is called net metering. Net meters can help you establish independence from the local power grid. But since this payment is capped at 50%, excess energy can be stored in a battery and used at night.

How effective are solar panels?

Factors affecting the efficiency of solar panels include:

• rated power – the maximum amount of energy that the system can produce, being in ideal conditions (equal to 1 kW of solar energy per 1 m2 of surface);

• the amount of sunlight that the panels can convert into electricity (depending on the influence of external factors);

• the material from which the panel is made (mono crystalline cells contain higher quality silicon, which improves performance);

• slope of the roof (the southern direction is better illuminated by the sun);

• angle of inclination (the best is from 30 to 50 degrees);

• the presence of shade, pollution and anything that blocks the light.

The power rating is the most important among these factors.

How do I check that my solar panels are working efficiently?

You can check the efficiency of solar panels using a home display – a wireless control panel to control the amount of energy generated. If you are concerned about their insufficient performance, you should contact the installer or manufacturer. It is not recommended to tamper with the solar panels as this may damage the system and void the warranty. High-quality solar panels for homes,  installed by, will provide you with reliable and efficient energy, saving you money.

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