To allow people to consider various options for powering appliances and
heating or cooling their vans, I offer the following magic formulas:

1 horsepower = 750 watts
Watts(power) = Volts X Current  Example , 14 volts X 90 amps, = 1290 watts

Factory AC Capacity, 12,000 to 20,000 BTU depending on year and compressor
upgrades.  This is common for all auto AC units.  The 4000 BTU unit will
work well while parked in the shade.  Traveling down the road with air
infiltration and the heat load, (sun, engine), you might be able to tell it
is there.  Remember ventilation must be left open.

For heat, 1,000 watts is 3,200 BTU
Gallon Gasoline 132,000BTU
Gallon Propane  98,000BTU
Gallon Diesel or Fuel Oil, 130,000BTU
12,000 BTU = 1 TON

From this information, you can make many conclusions as to power options for
various accessories.  Remember that to power motors, a large reserve is
necessary for starting.  Particularly AC units that may have to start the
compressor against a high head pressure.  If using an inverter, check that
it is designed to start motors.  Hope this information is helpful to
someone.

Dennis