Heating Economics?

40,000 BTU's of furnace versus 27,000 BTU's of heat pump. The furnace will output HOTTER air and IMO, will heat the Rv quicker and then shut off. The HP's will take longer to heat the RV as the heat oputput from the HP's is lower. BUT, running the genset for the HP's keeps all the 12 volt systems fully charged and supplies all the 12 volt and 120 power while it is running. Running the LP furnace's on 12 volts will deplete the coach batteries a little and you will have to run the genset at times to recharge the batteries. My vote is the HP's during the day and the furnace's at night. The furnace's deplete the batteries during the night as well as other 12 volt systems and during the day, when the genset is running the HP's the system batteries get recharged fully. Use a mix of both. Doug

I think you'll find that using the generator to make electricity is VERY expensive.

Say it's a 7000 watt generator. At half load you'll easily use .5 gallons per hour, or $1.88/3500 watts. That's $0.54 per kilowatt hour, like 4 times what shorepower sourced electricity might cost.

Someone else can take the math further, but I'd vote get a large propane tank. That might help your propane cost per gallon down too.

Well to clarify the situation a bit, in order to run the heat pumps, the genny has to be set to auto. The genny will then cycle on and off as required to run the heat pumps. To answer one of the other posters, there is no availability of park electric, as I am boondocking. Genny maintenannce is pretty minimal as I do all my own maintenance, and the parts and oil are not all that expensive. I am looking at it purely from a fuel source point of view. Sourcing the 2 fuels is not a factor, as propane and diesel is readily available, although I can run substantially longer between fills off of diesel rather than the propane.

Heat pump might be more efficient but the generator will drive the cost up.
A little Honda 1000 or some solar to keep the battery charged and furnaces running would be more efficient IMO.
If the big generator is running anyway to power the microwave or hair drier etc then you may as well run the heat pumps.

Are you asking for general info or are you planning to do this for an extgended time such as a week or longer? If it's going to be for a longer period and up to 24 hours per day (168 hours per week) then you'll also get into generator maintenance costs. There's not really any cost to running the furnaces other than if something breaks.

Could the answer be someplace in the middle?

Since you're talking about running the genny, we'll assume you don't access to commercial power and your profile doesn't say anything about having solar to charge batteries. Assuming the above, you'll have to run the genny probably a couple hours a day to recharge what the heat pumps and other electrical needs have used each day anyway.

I would run the furnaces set low at night. When I got up, start the genny, run the heat pumps, plug in a electric heater since you'll have spare amprage and charge the batteries. Make coffee, run the microwave, the water pump etc. With the MH warm and the sun comming up, you should have heat for several hours. Run the same routine at night for an hour or two.

I think this is the most practicle way to operate. I'll leave it to someone else to calculate the actual BTUs and pennies.

Bill

Heat pumps are a lot more efficient (even below 45) than a gas furnace. Having done the math for propane at $2.50 and elect at 12 cents it makes no difference if the electric is resistive and propane in even a 90% furnace... the cost is the same. Fortunately at home I heat almost entirely with a geothermal heat pump.
In the MH I have found that heating with my heat pumps is cheaper than using my diesel AquaHot. Even subtracting 20% for running the generator I'd still say the heat pumps are more efficient.
Since you put lots of miles on your coach I'd look into putting in a aux hot water heating unit that runs off your engine when going down the road and off the generator when parked.