I purchased a 1,500-watt modified sine-wave inverter for my boat, that will easily run my keyboard and amp for hours on end. Of course, the boat batteries consist of 4 T-105 golf cart batteries in a series parallel rig and a 400-ampere hour 12 volt battery. I can run an awful lot of stuff with this much power available.
Gary
interesting... could be an option when gigging at a garden party or bbq.. Not many can play where there is no power, it would set you appart from the rest..
But then the question is, what does it weight?