Off-Grid Solar Calculators

Appliance-specific

RV Air Conditioner Solar Sizer

A 13,500 BTU rooftop unit often runs around 1,200–1,800 W after start-up and needs several thousand surge watts. Four hours of afternoon cooling is already 6 kWh — a large lithium bank and array.

Inputs

W
h
W
h

Usable fraction of rated capacity.

System voltage of the battery or series string.

Results

Daily energy
6,000Wh
Battery capacity
526Ah
Array size
1,600W
Inverter surge to meet
3,500W

Recommended gear

Engineering methodology

Daily watt-hours = running watts × hours (Wh = P × t). Battery amp-hours = daily Wh ÷ (voltage × DoD). Array watts = daily Wh ÷ (peak sun hours × derate). Surge watts are passed through as the inverter surge you must meet; they are not added to daily energy.

Frequently asked questions

How many watt-hours does a 13,500 BTU RV air conditioner use?

Running power is often about 1,200–1,800 W after start. Four hours at 1,500 W is 6,000 Wh—before inverter losses. Start/surge (often a few thousand watts) must be met by the inverter but does not add those watts for four hours to the daily total.

Does a soft-start kit reduce the solar array I need?

Soft-start mainly cuts inverter surge, not running watt-hours. Array and battery still follow run watts × hours. You may downsize the inverter surge rating, not the daily energy.

Can I run RV air conditioning only from solar with no battery?

Only while the array and a grid-forming inverter can supply both running watts and surge with sun. Clouds and compressor starts usually still need a battery buffer. This tool always sizes a battery from daily Wh.

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