Calculators
RV power calculators
Sixteen calculators covering the whole RV electrical system, from a daily amp-hour budget through to wire gauge and fuse size. Every one shows its formula, labels published standards separately from planning conventions, and returns nothing rather than a guess when the numbers fall outside the tables.
Where to start
Work in this order: daily amp-hour budget, then battery bank size, then solar array size, then wire gauge and fuse size for the install. Every later number depends on the first one.
Batteries
Battery bank size
Work out the battery bank size your RV needs from your daily amp-hour use, days off grid and battery chemistry, with usa...
nominal Ah = (daily Ah x days) / depth of discharge
Run time at load
Work out how long an RV battery bank runs a given load, with the Peukert correction applied to lead-acid and correctly l...
hours = (nameplate Ah x depth of discharge) / load amps
Usable capacity compared
Compare what you actually get to use from a LiFePO4 bank against a lead-acid bank of the same nameplate capacity, includ...
usable Ah = nameplate Ah x depth of discharge
State of charge by voltage
Read RV battery state of charge from resting voltage for lead-acid and LiFePO4, and see why voltage is a poor gauge on l...
state of charge is interpolated from a published resting vol
Planning
Daily amp-hour budget
Add up what your RV actually uses in a day in amp-hours and watt-hours, appliance by appliance, so you size a battery ba...
daily Ah = sum of (amps x hours per day) for every load
Propane vs electric heat
Compare the cost of heating an RV with propane against electric heat for the same heat output, using published energy co...
propane gallons = BTU / (91,502 x efficiency); kWh = BTU /
Solar
Solar array size
Size an RV rooftop solar array from your daily watt-hour use and local peak sun hours, with a realistic system derate ap...
array watts = daily Wh / peak sun hours / derate
Charge controller size
Size an MPPT solar charge controller from array wattage and system voltage, with the cold-weather headroom that makes co...
controller amps = array watts / battery voltage, then add he
Solar charge time
Work out how long a solar array takes to replace a given battery deficit, using a realistic derate rather than nameplate...
hours = deficit Wh / (array watts x derate)
Inverters
Wiring
Wire gauge and voltage drop
Find the smallest copper conductor that carries your current within both a voltage drop target and a published ampacity ...
drop volts = 2 x run length (ft) x amps x (ohms per 1000 ft
Fuse and breaker size
Size a fuse or breaker for an RV circuit at 125 percent of the continuous load, rounded up to the next standard rating, ...
fuse amps = continuous amps x 1.25, rounded up to the next s
Charging
Generators
Shore power
Air conditioning
Frequently asked questions
- Which RV power calculator should I start with?
- Start with the daily energy budget calculator, because every other number depends on it. Once you know how many amp-hours a day you actually use, the battery bank calculator sizes the bank, the solar array calculator sizes the charging, and the inverter sizing calculator covers whatever AC loads you plan to run.
- Do these calculators use published standards?
- Where published figures exist, yes. Conductor resistance comes from NEC Chapter 9 Table 8, ampacity from NEC Table 310.16 and ABYC E-11, overcurrent sizing from NEC 210.20(A), and shore power ratings from the NEMA device configurations. Planning figures with no standards body behind them, such as depth of discharge, are labeled as conventions on every page that uses them.
- Is a 50 amp RV service twice a 30 amp one?
- No, it is more than three times. A 30 amp RV service is a single 120 volt leg at 30 amps, which is 3,600 watts. A 50 amp service is two separate 120 volt legs at 50 amps each, which is 12,000 watts. This catches a lot of people out, and an adapter between them never changes the amperage available.