Practical guide
How to Check RV Loads Against a Power Source
Use this guide when checking devices that may run at the same time. Power-source checks compare their combined demand with the ratings you enter for your inverter, generator, or shore power. Daily energy totals answer a different question.
1. Planning equipment or checking equipment you own?
Inverter Size and Generator Size estimate the AC output your selected loads require. They do not recommend a specific model.
If you already own the equipment, use Can I Run This on My Inverter? or Can I Run This on My Generator? to compare your loads with the equipment’s watt ratings.
2. Collect running and starting watts
For each AC device, find electrical input watts from its label, manual or a suitable measurement. Running watts describe normal operation. Starting watts are the total power a device draws during startup, not extra watts to add to its running watts.
Enter starting watts equal to running watts only for a device with no startup surge. The calculator does not estimate startup power using a generic multiplier. If startup is listed only in amps or VA, find the corresponding real power in watts before using a watt-based comparison. These units are not interchangeable.
List only devices supplied by this source and running together. Include a battery charger’s AC input if it is operating in that scenario, not its DC output.
3. Match demand to the right rating
Use continuous and peak AC output W for an inverter; running and starting W for a generator. Find these ratings in the equipment manual for the operating conditions you plan to use.
The result separates continuous demand, one unit starting while the others run, and all units starting together. For example, one 1,200/2,400 W device and one 100/100 W device need 1,300 W continuously and 2,500 W during startup. These numbers are only an example of the calculation, not preset values for any appliance.
Check peak duration separately. A watt comparison only checks watts; it does not verify apparent power (VA), current, voltage, waveform, or outlet limits. It also does not check battery or battery management system (BMS) capability, or reductions in equipment output under different operating conditions. A result that falls within the entered watt limits does not guarantee that the equipment will operate correctly.
4. Shore power uses running AC current
30 Amp Shore Power adds current for loads operating together and compares it with 30 A. Use each device’s running AC input amps. If you enter real power in watts instead, the calculator also needs the operating RMS voltage and power factor.
Power factor describes the relationship between real power in watts and volts × amps. It must come from device data or a suitable measurement; the shore tools do not assume PF = 1. If it is unknown, obtain running AC amps rather than guessing PF.
50 Amp Shore Power checks L1 and L2 separately. Identify a 120 V load’s leg from the RV panel documentation. A true 240 V load across L1 and L2 adds its current to both legs. Do not infer assignment from an appliance name or combine the legs into a 100 A allowance.
If you do not know which leg a load is on, do not guess. Confirm it from the RV panel documentation before using the calculator. These tools do not predict breaker trips or check branch circuits, adapters, startup or wiring safety.
5. Keep daily energy and power checks separate
A microwave used briefly can consume little energy over a day while still requiring substantial running and startup power. Keep both checks: daily energy use for battery and solar planning, and simultaneous loads for power-source ratings.
Each calculator includes its method, assumptions, and manufacturer references in the calculation details. For the principles shared across the tools, see How It Works.