One more answer to Niner's questions -- my old inverter was 400 watts, but it died of old age and overuse. I bought an 800 watt unit, thinking bigger is better, but it gives a low voltage reading when I am running my pump and my furnace at the same time. (When I read voltage at the battery, I have 12.7, but the inverter sometimes shows 12.0 or less.) . That is why I think this is a wiring problem -- it is like drinking a thick malt through a thin straw.
I use the inverter for minor things, like recharging my laptop and phone. So we still do need a little 120v power, even when boondocking. And yes, it has an on/off switch, to kill the parasitic draw when not in use.
