In can be quite confusing when you’re choosing solar panels for your home, as there are many different factors to consider.

How many panels do I need? where will they be mounted, will it be enough to power my home? how energy efficient are they? will be in series or parallel?

These are all great questions that I’m about to answer for you now including the formulas.

How Many Solar Panels To Power A House?

The number of solar panels required for a one-bedroom house is six panels, a three-bedroom home requires 10 panels, and a five-bedroom property will require 14.

The amount of electricity consumed by an average household each year is measured in kilowatt-hours (kWh) and ranges from 2,000 to 4,000 kWh.

Note: Most systems only require one inverter and one charge controller.

Related: How Long Does A Solar Panel Installation Take?


How many solar panels to run and power a house off-grid?

A three-bedroom house that is entirely off-grid would require around 4.4 kW of solar panel capacity.

A much smaller property may only need 2.2kW. This means you would need approximately 20-24 solar panels to generate enough electricity to power a three-bedroom house off the grid.

Alongside the solar installation, you would also need some form of battery storage, such as a Tesla Powerwall, to store the electricity generated during the day so that you have power at night.

This is based on the fact that solar panels don’t generate any power during the night.

With this in mind, let’s show you how to calculate the number of solar panels you need to power a house.

Related: Is It Possible To Charge Solar Panels Without Sunlight? MAYBE?

How about a camper van?

Camping vans with a typical electrical system that includes internal lights, a refrigerator, a TV, a laptop (on charge), and a mobile phone on charge use around 20 amps per hour under a full load (all of the above switched on) and 12 amps per hour on average usage.

This means you would need at least 2 x 100-watt solar panels to generate enough electricity to power a camper van.

As always, we recommend you speak to a professional solar installer who can help advise you on the best system.

Solar panel wattage

The majority of today’s residential solar panels are rated to produce between 250 and 400 watts each hour. The average capacity of a domestic solar panel system is between 1 kW and 4 kW.

This means that you would need between 4 and 16 solar panels to generate 1 kWh of electricity, depending on the panel wattage.

Series or parallel?

A series solar panel system is where each panel is connected in a line, with the current flowing from one panel to the next.

This is usually only used for very large systems as it can be more expensive and complicated to install.

A parallel solar panel system is where each panel is connected directly to the next one, with the current flowing from one panel to the other.

This is the most common type of system for domestic properties.

Your solar panel installer will let you know if your system will be series or parallel.

They will also let you know whether your fuse box can support the number of panels you need to reach your target capacity.

How Much Solar Power Will You Need?

Look at previous utility bills to determine your home’s average energy consumption.

Multiply your household’s hourly energy requirement by the highest sunlight hours for your location, then divide by a panel’s wattage, to figure out how many solar panels you’ll need.

To calculate your solar energy production, first, use a low-wattage (150 W) and high-wattage (370 W) example to establish a range.

Note that the size of your roof and the amount of sunshine it receives are also factors.

Don’t stress about the figures too much. Bear in mind that your solar installer will calculate the number of panels you need during the design and evaluation process.

Related: Can Mobile Homes Have Solar Panels?

How Many Watts Do You Currently Use?

Ok, take a look at your electricity bill and look for “Kilowatt Hours (or kWh) Used” or something similar. Take note of the length of time represented (usually 30 days).

There may be some of you who do not have this charge on your bill. If this is the case, look for the beginning and end meter readings on your bill to subtract the previous reading from the most recent one.

If you want hourly and daily usage numbers for our calculations, simply divide the monthly or annual average by 30 or 365 days before dividing it again by 24 to come up with your hourly average electricity usage.

Your answer will be in kilowatts. (And just to clarify, a kWh is the amount of power you consume at any one moment multiplied by the total time the electricity is being consumed.)

A house in a moderate climate might consume 200 kWh per month, whereas a large home in the south where air conditioners account for the majority of home energy use may require as much as 2,000 kWh or more.

The average American residence consumes approximately 900 kWh each month. That’s 30 kWh each day or 1.25 kWh each hour, for an average U.S. home.

Your target daily average is the average energy consumption you need your solar system to produce each day.

That’s the number of kilowatt-hours your solar system must generate if you want it to cover the majority of your power needs.

Solar panels, like any other energy source, have a minimum and maximum efficiency rate. Solar panels don’t function at peak efficiency 24 hours a day, which is why it’s critical to keep them clean.

Weather conditions are one example of this; your system’s efficiency may be temporarily reduced due to the weather. As a result, experts recommend adding a 20-25% buffer to ensure your system can still meet your needs.

How Many Hours Of Sunlight Can You Expect In Your Area?

The maximum amount of sunshine your location receives will have an effect on the energy your solar power system can produce.

Solar panels produce more electricity when they are exposed to direct sunlight. The amount of sunlight available in your area is measured by the solar insolation, which is a measure of the solar irradiance over time.

The Renewable Resource Data Center, which is run by the United States Department of Energy’s National Renewable Energy Laboratory (NREL), provides data on sunlight in all 50 states and major cities.

To convert your hourly energy consumption to watts, multiply it by 1,000.

For your region’s average daily peak sunshine hours, divide your average hourly wattage requirement by the number of daily peak sunshine hours.

This is the amount of electricity your panels will consume every hour to generate.

So, in a location that receives five peak sunshine hours each day, the typical U.S. home (900 kWh/month) would require 6,000 watts.

In the UK you can find out how many hours of sunlight your area gets from The Met Office.

What Affects Solar Panel Output Efficiency?

The following have an effect on solar output efficiency:

  • Temperature.
  • Energy Conversion Efficiency.
  • Solar Shadings.
  • The Orientation, Inclination, Latitude of the place, and Climatic conditions.

What Is The Effect Of Solar Panel Size?

If you have a small roof, or an unusually shaped one, you might not have the space to install as many solar panels as you need to meet your energy requirements.

As a result, you may want to consider installing larger solar panels.

Larger solar panels can generate more electricity than smaller ones, but they also take up more roof space.

Solar panel dimensions

Today’s typical solar panel sizes are 65 inches by 39 inches, or 5.4 feet by 3.25 feet, with some variation among manufacturers. The average solar panel weighs about 40 pounds.

As you can see, larger solar panels can take up a fair amount of space on your roof.

How big is one solar panel?

Solar panels are installed in arrays, with the number of panels varying based on the amount of space available and the quantity of power you want to produce.

A single panel usually has an area of 1.3-1.7m2, with 1.6m2 being the most frequent size.

The average home roof can hold a maximum of 12-15 solar panels.

In Summary

Now you know how many solar panels you need to generate the electricity you consume each month.

You also know the average size of a solar panel, and how much space you’ll need to install them.

If you have any questions about solar panel installation, or if you’re ready to get started, contact a solar installer in your area.

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About the Author

Passionate about helping households transition to sustainable energy with helpful information and resources.

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