Solar panels kWh calculator shows you how manly solar panels you will need to power your home and how much they will cost
Written by Andrew Sendy
Updated August 12, 2021
10 minutes read
Categories: Solar 101, Solar efficiency, Solar energy, Solar panels, Solar power, Utilities
The number of solar panels you need to power your specific home depends on your location and how much electricity your home uses.
The estimator above will calculate how many solar panels your specific house needs and other key solar information such as cost, payback period and savings.
The mini-estimator below will also show how many solar panels are needed to power your home and how much electricity they will produce, but will not show the other information.
How much will the solar panels I need to power my home cost?
The average cost of resdiential solar panel installation in 2020 is just under $3 per watt before the federal 26% tax credit. This makes a 7 kW system approximately $20,000 before the tax credit or approximately $15,000 after the tax credit. The solar calculator above will show you the average cost of solar panels in your city and the individual offers of solar companies near you.
How many solar panels does it take to power the average US home?
The average American 2000 square feet home uses approximately 1,000 kWh's of electricity per month and requires a 7.36 kW (7,360 watts) solar power system to offset this usage.
The most commonly used models of residential solar panels today are in the range from 300 watts to 360 watts. If we assume production from a 360-watt solar panel then it takes 20 solar panels to power an average 2000 square foot American home.
This is less than it was 2-3 three years ago when the wattage of the average panel was only 250 watts -280 watts, and so a few more panels were needed to get the same power output.
How does the calculator work out how many solar panels you need to power your specific home?
Each calculator converts the $ value of your electricity bill to kWh's of electricity used. It uses the current rates charged by your electric utility company to reverse engineer this figure.
It then uses NREL solar production data for each of the 3,000+ weather stations around America to work our how many kWh's of power 1kW of solar panels will produce on your roof.
If you use the calculator at the top of the page it will take into account the direction and tilt of your roof to more accurately calculate production and the number of panels you need. The mini-calculator does not do this.
The calculator at the top of the page also offers additional information such as panel placement, local prices on the size system you need and savings and payback period calculations for that system.
Can we calculate how many solar panels you need without needing to see your electric bill?
Yes. From the $ value of the electric bill, we can deduce your electric use because we have a current database of the electric rates charged by your utility company.
Will the number of solar panels I need to power my home fit on my roof?
It doesn't matter how many solar panels are needed to power a specific home if they do not fit on your roof.
The solar panel calculator at the top of the page also scans your roof, works out how much room you have for panels and lays them out in the best part of your roof.
Do my solar panels on my roof have to face South?
Solar panels facing South will produce slightly more power than solar panels facing other directions. However, only 10-15% more than panels facing east or west and so it is still fine to have panels facing other directions.
In fact, in states with time-of-use billing many installers are now recommending that solar panels be fitted on west-facing roofs to increase production in the afternoon peak electric pricing periods.
How long do solar panels last?
Solar panels last at least 25-30 years. If you use the calculator it will give you what is called a "payback period".
This is the amount of time it takes for the electric bill savings to pay for the upfront cost of the solar panels. After this point, the solar panels produce free electricity and pure profit for you.
What maintenance is required for solar panels?
Solar panels require minimal maintenance. In dry climates or where solar panels have been installed on a roof with a shallow pitch then it may be a good idea to clean the panels once a year or so. however, normally the rain does a pretty good job of this.
It is probably worth checking if junction boxes are still watertight every five to ten years, but other than this there should not be a need for regular maintenance.
Is the home solar calculator above smart enough to account for time-of-use electric plans
Yes. We have integrated with a partner called Genobility for our savings calculations and they maintain accurate rates charts for each of the utilities in America so that they can accurately forecast solar savings.
There are a number of states that are moving towards mandating time of use energy plans as a means to discourage the use of electricity at peak times (which it is more expensive under a time-of-use tariff plan). In California time-of-use electric billing will become mandatory towards the end of 2020.