Off-Grid Battery Calculator

Now that you've seen in our Off-Grid Battery Guide where the calculations come from, we've distilled all of that, and more, into our convenient battery array calculator. To find out more about each parameter and calculated value, hover over each name to see more details.

Continuous Load Continuous Load
The desired 24/7 wattage you want your battery system to deliver.
Battery Service Hours Battery Service Hours
The number of hours each day the batteries must supply the continuous load when the primary source (e.g solar) is not operating.
hours (20 recommended)
Depth of Discharge Depth of Discharge
The maximum allowed state of discharge for the batteries at the end of the battery service day, as a percentage. 1% is hardly discharged at all, 100% is completely flat.

Regularly discharging even deep-cycle batteries below 50% will greatly reduce their service life out of proportion to the delivered charge.
% (50% recommended)
Minimum Watt-Hours Minimum Watt-Hours
The calculated minimum total watt-hours needed by the battery array to meet your continuous load, battery service hours, and depth of discharge requirements.
Wh (calculated)
Battery Voltage Battery Voltage
The voltage of each battery in the array.

Use only similar batteries in each array.
Battery Capacity Rating Battery Capacity Rating
The capacity rating of each battery in the array, usually specified as the "20 amp hour rate".

Use only similar batteries in each array.
20-amp-hour spec
Battery Price Battery Price
Individual battery price, including core charges and sales taxes, if any.

Use only similar batteries in each array.
$per battery, incl. tax
Array Voltage Array Voltage
The desired overall voltage of the battery array. Using 24 volts instead of 12 volts will make most chargers twice as effective. See article for details.

Use only similar batteries in each array.
Batteries Per String Batteries Per String
The number of batteries in series in each string, totaling the array voltage. Multiple strings will be used in parallel to form the overall array.

Use only similar batteries in each array.
Battery Watt-Hours Battery Watt-Hours
The amount of watt hours supplied by each battery, calculated as the battery voltage times the battery rating.
Wh (calculated)
Raw Number of Strings Raw Number of Strings
Calculated number of battery strings needed to meet the design requirements. This number will be rounded up to calculate the total number of batteries.

If this number is just over a whole number, such as "3.100", then consider slightly reducing the continuous load or allowing slightly more depth of discharge to remove a full string of batteries.
(calculated, see hover note)
Number of Batteries Number of Batteries
The total number of batteries in the array needed to meet the design requirements.
Total Battery Cost Total Battery Cost
The total cost of all batteries in the array.
Total Array Watt-Hours Total Array Watt-Hours
The total actual available watt-hours in the array. This will be greater than or equal to the target watt hours.
Wh (calculated)
Actual Depth of Discharge Actual Depth of Discharge
The actual depth of discharge imposed on the batteries. This will be less than or equal to the specified depth of discharge.
% (calculated)
Use this calculator with actual battery values and prices to find out what battery options provide the best total system value for your needs. The lowest-price individual battery may not provide the lowest overall system cost.


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