Watts, volts, amps & time

Fill in any two of watts, volts and amps and the third is solved. Add hours to see the energy as Wh (what home systems are rated in) and Ah (what 12 V van and RV batteries are rated in).

Watts, volts, amps & time

Type any two of W / V / A. The third fills in. Hours turn it into energy.

Watts (W)

Volts (V)Battery 12 / 24 / 48 · AC 120 / 240

Amps (A)

Run time, hours per day

Battery / bus voltage	Ah per day	Amps while running
12 V	-	-
24 V	-	-
48 V	-	-
120 V	-	-
240 V	-	-

Same energy, different voltage: a 1,200 Wh load is 100 Ah at 12 V but only 25 Ah at 48 V. Battery labels quote Ah at the battery's own voltage, so compare Wh when shopping across voltages.

Enter two of watts, volts, amps.

Next: add up everything you want to run with the power consumption & battery sizing tool.

Planning figures, not a design. These calculators give you ballpark numbers to shop and plan with. They are not an electrical design, they cannot see your site, your loads or your local code, and they may be wrong. Wire sizing, over-current protection, grounding, rapid shutdown and interconnection must follow NEC 690 and your local code. Have any design checked by a licensed electrician before you buy or energize anything. You use these tools at your own risk.More on safety.