Calculate the number of solar panels you need to power your house

Calculate the number of solar panels you need to power your house

How do solar panels work? Your top 10 solar questions answered

Written by Andrew Sendy

Updated August 12, 2021

10 minutes read

Categories: DIY solar, Solar 101, Solar batteries, Solar efficiency, Solar energy, Solar panels, Solar power, Tesla

How do solar panels work

Solar energy sounds great, it’s good for the environment and can save you a fortune on your electric bills. Unfortunately, to the less experienced it can seem confusing. In this article we’ll address the questions many homeowners have about solar energy and hopefully eliminate any concerns you may have.

1. Do you really save money with solar panels?

Yes — a lot. Many homeowners save $80,000–$100,000 over the 25–30-year life of their solar system.

2. Can I get solar panels for free?

While solar is subsidized by the federal solar tax credit, it isn’t free. Although you can get a variety of zero-down solar loans/ leases, but you’ll still have to pay for the system.

The federal tax credit and declining equipment prices mean that your solar panel installation cost can work out to be less than you’d expect.

3. How many solar panels are needed to power a home?

A residential home on average will need 20–40 panels to wipe out all or most of their owners' power bill. The amount of panels you need can vary substantially depending on your power usage and region.

The map below shows how much power in kilowatt-hours (kWh) solar panels produce for each kilowatt (about 3–4 panels) installed on your roof. An average home uses about 28kWh per day; if you divide 28kWh (or your daily usage) by how much solar produces in your state, you can get an idea of how big your solar installation will be.

If we use this formula in southern California we discover that a home would need a 6.22kW system or about 21–25 panels to produce 28kWh per day.

4. How do solar panels work?

Solar panels are comprised of 60–96 solar cells. When photons (light) strike the surface of a solar cell it dislodges electrons causing them to flow. This is just what electricity is - flowing electrons. The electricity then flows into a solar inverter where the current is changed from DC to AC, which can be used by your home or exported to the grid.

5. How long will it take for solar panels to pay for themselves?

In the United States, solar panels take anywhere from 4–15 years to pay for themselves. The reason for such a variance in repayment times is because solar incentives and solar panel prices change from state to state. You can receive an accurate estimate on the cost of your solar panel installation with local incentives by entering your zip code below.

6. Can you buy and install your own solar panels?

You can — but it’s a murky road to go down. DIY solar kits are available online and at home depot, however, any cost benefits are canceled out by the added hassles. If you aren’t an experienced contractor you could risk injuring yourself or damaging your home. Since DIY solar only works out to about 15% cheaper, the vast majority of time it simply isn’t worth it.

Installing your own solar panels is a path I’d stay well away from.

7. Do solar panels add value to a home?

Homeowners are often concerned if they can sell a home with solar panels on it. But solar panels are actually an advantage instead of a hindrance in this regard. According to a recent report for every 1kW (about 3-4 panels) installed, your home’s value increases by $5,000. Who wouldn’t want to buy a home where they don’t have to worry about power bills?

Even if you don’t live in your home long enough for the system to pay for itself, the increased property value should make up for your solar panel cost.

8. What are the best batteries for solar power?

The Tesla Powerwall is by far the best battery both price-wise and in terms of functionality. That being said, solar batteries aren’t actually necessary, especially if your state offers net metering.  

Net metering is a law that requires your utility to compensate you for excess electricity sent to them by your solar panel system. There are two ways solar arrays save their owners money:

  • Supplying power for your home’s domestic need (replacing power you would have bought from the utility)
  • Exporting energy to the grid to be credited by net metering

Provided your system is sized correctly, your solar panels should actually produce more energy than your home needs. This excess energy is exported to the utility grid and earns you credit on your bill. These credits compensate for the times your home must draw energy from the grid.

In most states, your utility must pay you at the full retail rate you purchase power at!

9. How much is a Tesla Powerwall battery?

The Tesla Powerwall costs $6,700 and then an additional $1,100 for the supporting hardware. The supporting hardware can support up to 10 Powerwalls. In the table below you can compare the Tesla Powerwall price and storage capacity to batteries by Sonnen and LG. All the products below are new lithium-ion batteries, Tesla, Sonnen, and LG no longer manufacture harmful lead-acid batteries for home energy storage.

Battery brand

Tesla Powerwall 2

Sonnen eco



13.5kWh (useable)

10kWh-20kWh (model dependent)




$17,000 (10kWh model)


Don’t view a home battery system as an investment- you won’t receive a good return. Instead, view it as a source of backup power during an outage. Like most new, up-and-coming technology it’s expensive, and early adopters do so out of interest and not for financial gain.

10. Which is the best solar company?

LG, Panasonic and SunPower are the top 3 best-reviewed panel brands. If you’re looking for installer reviews, feel free to visit our solar companies section for thousands of reviews across America.

Author: Andrew Sendy Andrew Sendy LinkedIn

As chairman of Solar Investments Inc and chairman of the largest solar panel installation company in South Australia, Andy is passionate about solar power. With his unique working background he writes on the residential solar industry in America from a unique perspective.