Solar Panel Sizing Calculator

The 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. This calculator assumes and adds for inefficiencies in batteries, panels, and wiring. It is only an estimate.

Battery Bank Sizing

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

Step 1:

Your Daily Energy Usage:

Example: 14 amps x 240 volts for 8 hours = 27000 wh

 

 

Watt Hours per Day: (Amps x 240 volts x hours) You can take monthly kwh from electric bill and divide by 30 for daily wh total

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?

Step 3:

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

What is the lowest temperature your battery bank will experience?

Degrees (Florida and Bahamas choose 80F)

Results:

Select a battery bank voltage:
Note: All calculations assume a 50% discharge to your batteries to optimize battery life and 10% inefficiency

 

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. This is the 'Isolation Value'

Select the State-City Closest to your location (currently only US states are provided)

or

Manually enter the average sun-hours for your location.
Florida and Bahamas = 5

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

You will need panels for a total of watts.

Sizing your Solar Charge Controller

You will need a charge controller that can handle amps

A Flex 80 from Outback can only use 5000 watts of panels at 80 amps, so if your total wattage exceeds 5kw you need to add additional charge controller.

 

 

Energy Requirements

To sustain your entire house, you need to average your daily use of electricity. Your electric bill probably details your average daily use or presents a one-year total. Dividing the one-year total by 365 calculates your daily average. As an example, if you used 6,000 kilowatt-hours (kWh) in a year, divide by 365 to calculate your 16.4 kWh daily average.

Target Daily Average

Solar panels do not always operate with maximum efficiency. The system may lose stored power or inefficiently collect solar energy. There may also be sustained periods of insufficient sunlight. Therefore, adding a 25-percent cushion protects your system from running out of juice. Multiplying your 16.4 daily average by 1.25 calculates a target daily average of 20.5 kWh.

Daily Peak Sunlight Hours

Solar panels rely on the sun to capture electricity, so your panel needs are directly related to the amount of sunlight you get. TheRenewable Resource Data Center provides this information for your state and further breaks it down by major city. Dividing the daily requirement by the number of daily peak sunlight hours calculates the amount of energy your panels need to pick up every peak sunlight hour. Continuing with the example, if you lived on Daytona Beach, FL, with 5.2 daily peak sunlight hours, divide 20.5 by 5.2 to calculate 3.94 kW required per hour. Multiply KW by 1,000 to convert the measurement to watts. In the example, multiplying 3.94 times 1,000 converts the figure to 3,940.

Number of Panels

Solar panels are available in a wide range of wattages, such as 100-W or 200-W models. The wattage of your panels determines the number of panels you need. Dividing your hourly requirement by the solar panels wattage calculates the total number of panels you need. In the example, dividing 3,940 W by a panel's 200-W rating calculates 20 panels needed to sustain your entire house.

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