When I go for a motorhome, I'm debating on a 1000 watt model, just because it is lighter and saves space. If I need more than 1500 watts, it may be easier for me to just flip the onboard genset on. A 1000 watt model is nice for saving fuel, if one just needs enough power to keep batteries charged. It also comes in handy should the house batteries be so low that they can't start the onboard generator.
For an auxiliary generator, a 1000 watt model can come into handy. However, if one is needing a "main" source, I'd steer them towards two 2000 watt models, or even a 3000 watt model (although they are back-breakers if one doesn't have a ramp to get them in place and out.)
Whatever you do, unless money is a dire situation, do not go for the 800-1000 watt ET800 clones that are sold for about $100-$150. Almost all are unregulated, and are not engineered to handle electronic devices, so can cause damage with electrical spikes. Those ET800 clones might be useful if using an external charger, but that is it. I'd never want one near my rig's electrical system.
