Two numbers matter
Running watts are what appliances consume after startup. Starting or surge watts are the short higher demand some motors and compressors require when they start.
Do not simply add every surge
Not every appliance starts at the same instant. A useful planning approach identifies the expected running load and then considers the largest additional startup event likely to occur while those loads are already running.
Air conditioners need special attention
RV air conditioners can have significant compressor-start demand. Soft-start devices may reduce startup demand, but use actual specifications for the installed air conditioner and soft-start system rather than assuming a generic reduction.
Altitude and temperature can reduce output
Portable engines can produce less power at higher elevation and in demanding environmental conditions. Follow the generator manufacturer’s derating guidance if the RV is regularly used at altitude.
Leave operating headroom
Running continuously at the edge of a generator’s rating can be undesirable. A reasonable reserve also helps when chargers, converters or cycling appliances change the load unexpectedly.
Check connection limits
Generator output, receptacle ratings, RV shore-power configuration, adapters and transfer equipment all need to be compatible. A large generator rating does not make an undersized connector or circuit acceptable.
Common questions
What is the difference between running and starting watts?
Running watts are the sustained load after startup; starting watts are the short surge required by some motors and compressors.
Should I size a generator only from the RV air conditioner?
No. Include the other loads expected to run at the same time and use actual appliance specifications when possible.
Open the related TowAtlas calculator and use your saved Garage setup when available.