Yeah I mean they're not great, but for that much money one could buy a pair of the Honda 2000w inverter generators and run them on natural gas and cycle between them quite handily. Have the "on" generator and the "just off of the latest rebuild cycle" generator.

I've also thought that if one could figure out some of the power electronics a wrecked Prius engine just ticking over at idle would probably provide most of your off-peak power and charge batteries and then during peak times it could just ramp up a bit. I've never heard of a natural gas conversion though so it would be a long road I suspect.