Off-Grid Solar Calculator

Inputs

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Daily AC energy consumed by the loads. Sum appliance wattage times hours per day, then divide by 1000.
kWh/day
Average full-sun equivalent hours per day for the design month or season.
h/day
Usable daily output after temperature, dirt, wiring, charge controller and other losses.
%
Extra PV wattage after covering the calculated daily DC energy.
%
AC load energy divided by DC battery energy. Used to convert daily AC energy to required DC energy.
%
Number of days the battery should support the daily load without useful solar charging.
days
Higher DC voltage reduces battery current and charge-controller current for the same power.
Fraction of installed nameplate battery capacity assumed usable after depth-of-discharge and reserve derating.
%
Largest continuous AC wattage expected at one time.
W
Highest short-duration surge wattage expected from motors, compressors or tools.
W
Extra continuous inverter capacity above the entered peak continuous AC load.
%
Safety margin applied to the estimated charge-controller output current.
%

Results

Default result
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PV array size (P_pv)
1,383 W
Pass

PV watts after 75.0% derate and 20.0% margin.

Also computed

Battery bank capacity (C_batt) Pass 202.5 Ah

48 V bank; installed Wh divided by 48 V.

Installed battery energy (E_batt) 9.722 kWh

Usable autonomy energy (E_use) 7.778 kWh

2.00 days of DC load before usable-capacity derating.

Charge controller current (I_cc) Pass 36.01 A

estimated MPPT output current at 48 V with 25.0% margin

Inverter continuous rating (P_inv) 1,500 W

Inverter surge rating (P_surge) 3,000 W

entered surge load controls

Method notes 4 notes
  • Daily DC energy is daily AC load divided by inverter efficiency.
  • PV array watts = daily DC Wh / (peak sun hours x array derate) with the entered sizing margin applied.
  • Battery Ah is installed battery Wh divided by DC system voltage after usable-capacity derating.
  • Charge-controller current is a simplified MPPT output-current screen. Final solar design must check module string voltage, controller limits, conductor sizing, overcurrent protection, grounding, disconnects, battery chemistry, temperature, listings, adopted code and permitting.

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