At 03:09 PM 2/14/2010, george jannini wrote...
>if it came down to a situation when we might want to run, say,
>an electric heater in addition.

An electric heater would be, arguably, the worst use of a generator,
due to multiple levels of efficiency loss (there's probably more heat
going out the exhaust/engine/generator, than there is being produced by
the heater). Look into a propane or kerosene catalytic, if heat is a
concern.

A 110V electric heater will typically have 750/1500W (2500/5000 BTU)
settings. That's a significant portion of generator output. One of the
small propane catalytics which fits on a 1 lb bottle will put out 8000+
BTU for a couple of hours. A kerosene heater can do better still in
BTU/runtime.

The BA-6 gasoline heater, an option on some Vanagons, is rated at about
22,000 BTU (~6400 watts), at over 3 hours per gallon of gas. Try to
find a 6500 W generator which will do more than a small fraction of
that.