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How Many Solar Panels Do I Need?

Updated for 2023

How Many Solar Panels Do I Need?

Two of the main reasons people consider solar energy for their homes is because they want to save money on their energy costs and reduce the impact they’re making on the environment. Solar panels are a significant investment and can cost between $15,000 and $20,000. 

If you decide you want to go solar, it’s important to do your research. Be familiar with how solar panels work and are installed and determine how many you may need to provide ample energy to your home. You’ll also want to get a few estimates, but only from trusted, reputable companies who are experts in solar power installation.

How Do You Determine Your Energy Requirements for Solar Panels?

There’s no one size fits all solar panel installation. Each system is highly individualized and depends on several factors including the size of your home and roof, the amount of direct sunlight your home receives and how much energy your home uses. 

But you can get a good idea of what you’ll need before talking to a professional installer. It’s important to note, the square footage of your home is not necessarily the most important factor, but how much energy your home uses on a daily basis.

A watt is the basic unit of measurement for electrical power. Kilowatts are used to measure residential power and one kilowatt (kW) equals 1000 watts (W) of electrical power. So, one kilowatt hour (kWh) is equal to 1000 watts of energy use over the course of one hour.

The U.S. Energy Information Administration says U.S. residential utility customers, on average, used 866 kilowatt hours a month in 2021. How many kWh you use will be on your electric bill. How much you used for that month, as well as a year-to-date amount should be on your latest utility bill. To figure out how much kWh you will need each month – divide the year-to-date amount by 12. So, for a home that’s used 12,000 kWh for the year, it would be 1000 kWh a month.

  • 12,000 / 12 = 1000

Your solar panel system will need to produce 1000 kWh a month to generate enough electricity for your home to be 100% solar.

What Size Solar Panel System Will I Need?

Once you figure out how much energy you consume a month, you’ll want to determine what size solar panel system you will need. To do that, take the same year-to-date number on your electric bill and divide it by 1200 to determine what size solar panel system you will need to produce 100% of your energy use. For example, if you used 12,000 kWh for the year, then you’ll need a 10 kW system. 

  • 12,000 / 1200 = 10

Residential solar panels can give you between 150 – 370 watts. Aim to install panels that produce 350 watts or more. Keep in mind, the lower the number – the less efficient the panels are. So, that means you will need more solar panels. That’s where your roof space will become important. If you have a chimney, rooftop air conditioning unit or skylights that will take up space and lower the number of panels you will be able to install.

To determine how many panels you need, divide the wattage of your system by the wattage output of your solar panels. So, a 10 kW system produces 10,000 watts. If your panels generate 350 watts, you’ll need about 29 solar panels.

  • 10,000 / 350 = 28.5

What Affects Solar Panel Output Efficiency?

Just because the sun hits a solar panel doesn’t mean it will result in energy production. According to the U.S. Department of Energy most of it is lost because of the way solar cells are designed, limiting their ability to produce energy from the sunlight they receive. Researchers around the world are working on improving this.

Cloud cover can also, obviously, effect the amount of energy your solar panels produce. But the intensity of the sun can also hurt efficiency. When higher temperatures hit the solar cells, it can decrease the voltage and not produce as much energy. Higher temperatures can also damage the cells and result in a shorter lifespan for the panel.

Gridlines on solar panels can cause a decrease in efficiency because they reduce the active surface area. Gridlines can also peel, which can cause problems for energy output.

It’s important to make sure you get your solar panels from a reputable company who are experts in solar panel installation because subpar construction can cause the panels to corrode, crack and not effectively absorb sunlight.

Which Regions of the U.S. Are Solar Power Most Effective?

Solar panels can be installed on any home in the United States. But some parts of the country are better for generating solar power than others. And while much of it has to do with places that see the most sunshine, the incentives that states offer to encourage homeowners to go solar also plays a significant part. 


The Golden State enjoys sunny or partly sunny weather for most of the year and it offers several incentives for residents who want to go green, allowing solar panel systems to pay for themselves in about ten years. California also invests more money in solar technology than any other state – to the tune of more than 70 billion dollars – and has more job opportunities in the solar power industry.


Arizona’s desert climate gives it plenty of sunshine for much of the year. The state offers tax credits, as well as sales and property tax exemptions to encourage residents to invest in renewable energy. Homeowners will see the system pay for itself in roughly seven years.


Colorado was the first state in the country to put a statewide renewable energy portfolio standard into place. The state offers several incentives that result in the solar panel system paying for itself in about eight years.


The state of Connecticut is encouraging solar power usage by requiring its utility companies to generate 27% of their power from renewable energy. It also offers homeowners some nice incentives that will help the system pay for itself in about eight years.

New York

New York is one of the states leading the way in solar power initiatives, requiring utility companies to generate at least 30% of their energy from renewable resources. Homeowners can take advantage of several incentives, which helps the solar panel system pay for itself in about eight years.

There are several factors to consider when deciding whether to go solar. Doing your homework on solar power systems, knowing what your state offers in tax incentives and understanding how much energy your home consumes will go a long way in ensuring you make the best choice for your family.