My wife is pushing for a microwave
in our Boler
, even for use without an outside AC power supply. Her reasoning is that the massive power draw is so brief that the total consumption should be acceptable. If you accept this logic, the only remaining challenges are to select an appliance and to arrange the power supply.
The alternative to an expensive 12V DC appliance is an inverter
supplying an ordinary AC appliance. The DC current draw is the same (actually even worse due to inverter inefficiency), but the wiring should be less of a problem, because the inverter can be right beside the battery: thick and short 12V cables, with a AC power cable (from inverter to appliance) which is not a problem (because it only carries a few amps at the higher voltage). I don't know if the power characteristics of cheap inverters are okay for a typical small microwave (I wouldn't be buying a true sine wave inverter for this), but if cheap units work then enough capacity now costs about a hundred bucks.
I agree with Dan's concern that 50 amps (for instance) is a lot of draw, so the battery needs to be large enough for the current (not just the total stored energy). Deep discharge batteries are better for RV use starting batteries by giving up something, and what they give up is peak current capacity
, but 50 amps is only one eighth of what my old four-cylinder Toyota car pulled while starting, so it might not be unreasonable (for a short time) for some of our battery setups.