Worth buying a Hymer Sunlight and upgrading it?

The engine needn't run ALL the time... only if you have an excessive need for 120v power. It comes with lots of battery power (most seem to have the lithiums), so perhaps only at times of extreme heat to run the AC. Your batteries will even handle a short microwave run.

I've read various comments on fuel usage when idling to use this. Some say it uses less gas and it is certainly much quieter and dependable than an Onan.