Adding high-wattage 120 volts to the tow vehicle

I've had low-wattage inverters in my vehicles for about 15 years, very nice to recharge cell phones and laptops on long trips when you don't have the car adapters.  I've run household fans at drive-in theaters, powered lights and a small television (on the road before LCD televisions were available, and when the power went out at our last house).  Even powered a crock pot once when we were running late for a family dinner and it needed another 30 minutes to cook, so it cooked on the road.  The car smelled like a kitchen for a week. 

 

Primary uses for this mod would be to run the "big stuff" on the 'pod at times, and to run an electric chainsaw when I need it away from home.  I have a stationary 12kw generator and a 6kw inverter, so I'm no stranger to backup power.  The whole-house inverter was a home-built project, repurposing a UPS from eBay and doing all the wiring and conversion myself including creating a 22kw battery bank.

 

My options are roughly the same for under-the-hood.  There are a few 120 volt add-on generators available.  Custom fabrication is necessary to create a mount, which isn't cheap.  The generators aren't cheap either.  I just found one that puts out 5kw but it also costs $5k.  Ouch.  I didn't look very hard for something in the 2kw-3kw range.

 

I could also go with an inverter.  A high-output alternator to drive it would be around $300 and would be bolt-on in place of the existing alternator.  Extra-heavy-duty versions with more complex rectifiers have good output at idle and don't cost much more.  A 3kw full-sinewave inverter can be bought for $1500.  So about $2000 complete after adding wiring.  Advantage here is I can run low-wattage items when the vehicle is off.  When I get a new tow vehicle I can take the inverter with me.  I can't use the inverter I have at home.  It is very large and doesn't run off of 12 volts like a standard automotive electrical system.

 

I could just buy a Honda or Kipor 3kw genset for $2000-$3000.  But its an extra brick to haul around and move around, keep gassed up, maintain, etc.  Not quiet, either.  Not an option for me.

 

Stats I've found online say vehicles use about .15 to .2 gallons per hour idling.  Found a few that said its 1 gallon an hour but that sounds high to me.  While not ideal that wouldn't be much gas if an overnight stop at a truck stop or Wal-mart was needed and it was still 90F outside at 10 o'clock at night.  We could cook dinner with the microwave and then turn on the A/C.  Since the tow vehicle would be quiet we could even do this at campsites with no hookups.

 

3kw comes out to 4 horsepower, probably less than a 250 hp engine wastes when idling, and even if it is a bit of a load modern engine computers automatically compensate when accessory loads start so the engine doesn't stall.  So I think mechanically its doable w/o modification. 

 

One problem is how to ensure the tow vehicle stays immobile since it will be sitting there with the key in the ignition.  I understand steering wheel locks are useless because they can be removed with a can of refrigerant in seconds (spray, freeze the metal, crack with hammer).  So something else will have to be obvious to deter, and effective if it isn't enough of a deterrant that they smash the window and hop in.

 

Ok, your turn.  Poke some holes, make some suggestions.  Point and laugh!