RV shore-power calculator: total and per-leg loads

Compare running input watts against the stated shore-power source. For 50-A service, enter the leg 1 allocation to check the two legs separately; leaving it blank means neither leg is checked. Treat current estimates as power-factor 1 arithmetic, not an electrical approval.

Use the actual source after adapters and other limits;50 A has separate limits on two legs.

Use safely obtained voltage information. This tool does not decide whether the voltage suits any appliance.

Use the actual documented value for the intended operating conditions.

Running input watts for the exact unit; motor starting and power factor still require separate checks.

Actual electric input; zero if not operating electrically.

Electrical input, not cooking output.

Actual AC input demand under the intended charging load.

All other simultaneous AC input watts. Do not add loads served separately unless they draw from this source.

Optional for 50 A: assign part of the complete entered watt total to leg 1. The remainder is assigned to leg 2. Leaving this blank means neither leg is checked.

This form compares the entered electrical loads locally when JavaScript works. Its server fallback provides the same supply arithmetic on a separate results page.

Supply capacity and actual appliance watts differ

Cummins’ power basics compares 30-A120-V shore supply with 3600 W and 50-A240-V supply with 12000 W nominally. Volts times amps gives apparent power; real watts also depend on power factor. Use actual current and circuit requirements for the installed equipment.

The 80% line is a chosen planning allowance. Required sizing depends on actual equipment, load duration and applicable installation rules. This tool does not automatically declare every load above that line prohibited or every load below it acceptable.

A low average can hide an overloaded leg

Assume 50-A service at 120 V with 8400 W total: 6600 W on leg 1 and 1800 W on leg 2. At power factor 1, the currents are 55 A and 15 A. The average 35 A and total below 12000 VA do not remove the first leg’s overload.

Assumed leg allocationLeg 1: 6,600 W; Leg 2: 1,800 WAssumed leg allocationLeg 1: 6,600 WLeg 2: 1,800 W

Enter 6600 as the leg 1 allocation for that complete 8400-W load list. The tool assigns the rest to leg 2. Do not enter one leg’s load twice by adding it again to Everything else; the allocation divides the existing total.

Check a source before relying on a resultIdentify actual source and approved connection ratingsThen: List every simultaneous running load and its circuitThen: Verify leg allocation, start behavior and exact equipment limitsCheck a source before relying on a resultIdentify actual source and approved connection ratingsList every simultaneous running load and its circuitVerify leg allocation, start behavior and exact equipment limits

Two air conditioners are an equipment question

Two assumed 900-W running loads total 1800 W, so their count alone does not prove a 30-A overload. Startup, power factor, other loads and manufacturer approval remain separate. A soft start does not erase running current or fix a damaged supply connection.

The calculator does not apply a universal 108-V damage threshold. Follow the appliance’s operating limits and the protective device’s actual functions. Stop at damage or repeated trips; do not open a pedestal for live testing.

Script calculation stays on the device; fallback calculation submits entries to this site. Use shore-power connections and generator matching for the decisions this running-load estimate does not settle.