I have a 28'5" Class C It is equipped with ducted air conditioning and a heat strip.
To test how well it heats I deliberately ran only the heat strip last night.
Outside temperature was 5C (41 F) and inside was 17 C (62.6F) . So a delta of 12 degrees C (21.6 F).
The thermostat was set at 20 C (68F).
Fan speed was set on low.
The RV started out at 6 C (42.8 F) and rose to 17 C (62.6F).
Run time was 100% duty cycle for 7.5 hours.
Start time was 11:00 p.m. so there was no "solar gain" happening.
Overnight Low was 3 C (37.4 F) and at 6:30 a.m. out door temperature was 5 C (41 F).
No one was inside the RV so no gain from the human factor.
Converter was on--no other devices active. The batteries were fully charged, so I ignored any waste heat from it.
RV was plugged into a single 15 amp circuit.
I decided to do some measurements on the air conditioner and heat strip in watts. The readings were the peak over a five minute run time. The fan on low readings seem to be stable. All readings include a 4 watt parasitic load (probably from the display on the microwave?)
222 watts fan on low no heat
250 watts fan on high no heat
1408 watts heat strip on with fan set to low
1422 watts heat strip on with fan set to high
It would appear that the heat strip is about 1186 watts maximum, or 3186 btu's.