Is the drill battery powered that needs recharge or an 12 amp 120v industrial hammer drill?
Otherwise for small stuff I use 300w Go Power sine wave inverter.
Plug the main cord in is fine as long as fridge and water heat are set to propane only and converter, microwave, air conditioner stay off. You need 1800 watts and four batteries to run the microwave.
I power my tv, dvd, laptop and charge small items with a Go Power 300w sine wave inverter. You might be fine with 150 watts.
I mounted the inverter hidden behind the fuse-breaker panel. 12v connects to the main battery feed to the panel. 120v is wired into the entertainment area circuit with an automatic transfer switch. The wiring is very straight forward if you have done any home wiring before. The Go Power 300w has a provision for a remote power switch so with the touch of a button I have instant power.
GP 300w SW $160
Xantrex 15 amp switch $49
So all in maybe $250-$300 for self install.
Morningstar also makes a good 300w inverter.