Off grid solar system calculator

off-grid pv systemJPG

Our Off-Grid Solar Panel System Calculator helps you size the battery bank, watts of solar panels and the solar charge controller you need. The calculator assumes you will need to size your system to get you through average amount of sun-light in the least sunniest month of the year for your location.

Battery Bank Sizing

This calculator will help you size the battery bank for your system.

Step 1:

Your Daily Energy Usage

Watt Hours per Day:

This value is usually printed on your electric bill. Take your monthly kilowatt-hour usage from your electric bill and divide it by 30 to get your daily kilowatt-hour usage. Since it's in kilowatt (1000's of watts) you'll need to multiply that number by 1000 to get the number into watt-hours. If you don't have a bill, or don't know your consumption, please use our Load Calculator to go through the steps to determine this value.

Step 2:

How Many Days Should Your System Run without Sun?

How many days of backup power do you want in case of cloudy/rainy days?
(when your solar panels will produce little energy)

Step 3:

Adjust the Effective Capacity of Your Battery Bank Due to Low Temperatures

What is the lowest temperature your battery bank will experience?


Results :

Select a battery bank voltage:

Note: All calculations assume only a 50% discharge to your batteries to optimize battery life.

  Solar Panel and Solar Charge Controller Sizing

This calculator helps you size the solar panel's and charge controller's needed for your system.

Step 1:

Determine the Solar Exposure for Your Site

You need to determine the average number of sun-hours per day during the least sunniest month of the year.

Manually enter the average sun-hours for your location.

Step 2:

Sizing Your Solar Panel Power Needed

The total wattage of Solar Panels that you need is:

Watts, or kilowatts

This value takes into account losses due to system inefficiencies.

Step 3:

Determine How Many Solar Panels You Need in Your Array

How many solar panels do you need? That depends on the panel you choose.

Select the wattage of the panel your interested in, and see the results below:

watts per panel



Results :                                                                                                                  

You will need panels for a total of watts.

Sizing your Solar Charge Controller

You will need a charge controller that can handle amps