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How Many Solar Panels Do I Need To Power A House? What You Need To Know!

house powered by solar energy

There are many factors that determine the number of solar panels you will need to power your full house. The biggest determining factors are the amount of power you use, the efficiency and power output of the solar panels, and the amount of sun your house receives.

A typical home requires takes around 20 to 25 panels at $20,000 for the whole system, and it is important that you get the figures right, or you could end up with redundant panels that generate power you can’t use or not enough panels so that you still have to draw some power from the grid.

Fortunately, it is quite easy to determine the exact number of panels you require, as long as you have access to certain pieces of information.

Read on to see how to calculate the number of panels you need and whether there is anything you can do to reduce the cost of a solar system installation.

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How Do Solar Panels Work?

A solar panel is a collection of photovoltaic cells. As particles of light, called photons, pass into the cell, they knock electrons from atoms which generates electricity. This passes through an inverter and is passed into the house, where it is converted to alternating current energy and can be used to power the electrical devices in your home.

Modern solar panels are much more efficient than earlier models and can work in areas with low sunlight, although the more sunlight the cell receives, the more power it will ultimately generate.

To get the most efficiency, it is common to have solar cells installed on the roof of the property where they will be exposed to more sun. A professional installer will be able to determine the best placement for solar cells and should be able to help you determine the exact number of cells you need. But, if you’re looking for a guide so that you can determine the price of a solar system, or the amount of space your solar panels will take up, you can use existing power demand and sunlight figures to make a basic calculation.

solar panels on the field
Image Credit: Pixabay

Calculating The Number Of Solar Panels You Need

Use your energy bills, solar panel power output ratings, and the number of sunlight hours your home receives, to calculate the number of panels you require.

Home Power Usage

Electricity usage varies greatly from one property to another, but also from month to month and day to day. Most homes use more electricity in winter when lights are on longer and heating systems and heaters draw more power.

Electricity usage is measured in kilowatt-hours, or kw/h, and is the number of kilowatts of electricity you use in an hourly period. Your energy bills should include this information. Use your bills to calculate how much energy you used in the past 12 months and try to get a more detailed breakdown so that you can see your maximum 24-hour usage.

An average US home uses just over 10,000kWh per annum or around 20kWh per day.

solar panels on house roof
Image Credit: Pixabay

Solar Panel Power Output

Not all solar panels are the same and while there are some highly effective and productive panels on the market, there are smaller devices with a lower output. A typical panel will generate anywhere between 200 and 400 watts of power. This is how much power the panel can output at any time, and you will need to multiply that figure by the number of hours of daylight you experience in a day. If you get four hours of sunlight per day and have a 250-watt panel, it will generate 1,000 watt-hours per day or 1kWh.


The exact amount of sunlight that a solar panel is not necessarily the number of daylight hours per day. Factors such as cloud coverage do have an effect, and you have to bear in mind that you will enjoy fewer daylight hours in winter than in summer. Even the height above sea level of your property will have an effect, and if your home is surrounded by large trees, these will reduce the amount even further.

For the sake of calculating your solar requirements, assume that your panels will receive four hours of sunlight, on average, per day. You can use solar insolation maps to help get a better picture of exactly how much sunlight you can expect.

technician fixing solar panel
Image Credit: Pixabay

How Many Panels Do You Need?

Assuming that you are installing 300-watt panels, you receive four hours of usable sunlight per day, and you use 10,000 kwh per annum, this means that a single panel would generate 1.2kWh per day or 438kWh per annum. 10,000 divided by 438 equals 22.8, so you will need 23 solar panels to generate the amount of electricity you use every year. Replace the figures with your own to determine exactly how many panels you need.

Cutting The Costs

A typical solar system costs around $20,000 to install, so if you spend $180 per month on electricity, it would take nearly 15 years to cover the cost of the solar installation, assuming that you don’t have to pay for any repairs or general maintenance to the system and that you do manage to generate all the electricity you require throughout the year.

Energy Efficiency

Short of moving somewhere sunnier, there are other ways that you can improve the cost-efficiency of a solar system. For a start, you should ensure that you are using more energy-efficient appliances and lights and run your heating and air conditioning less.

solar panels on house roof
Image Credit: Robert Kneschke, Shuterstock

Tax Credits And Rebates

There are also tax credits available for those that install a new solar system, and some local authorities offer rebates and other savings that can reduce the cost of installation by thousands. A good installation company will be able to point you in the right direction for these rebates., and you should always shop around to ensure that you’ve getting the best deal.

How Many Solar Panels Would Be Needed To Power The U.S.?

The U.S. uses approximately 4000 billion kWh of electricity per annum, which means that you would need approximately 7 to 8 billion solar panels to generate enough electricity.

Can You Run A House Entirely On Solar Power?

As long as you do your calculations correctly and have enough solar panels installed, it is entirely possible to run an entire house and all of its appliances, heating, and air conditioning, using solar power.

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The exact number of solar panels needed to power a house varies according to the power used in the house, the amount of sunlight the house receives, and the power output of the panels. On average, a U.S. home would take 23 solar panels and the system would cost approximately $20,000 to install, although there are grants and tax credits available that reduce this cost. Using the calculations above, you can get a more accurate picture of exactly how many panels you require.

Featured Image Credit: Robert Kneschke, shutterstock

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