Our household is using LESS energy ... ONLY because we're more efficient. Our PV setup was based off our former usage ... using an inefficient washing maching, AC, fridge, and incandecent lighting. Ergo, we have a surplus credit with the electric company. We ARE less anal about clicking lights off now days ... and feel less paranoid about gazing into the fridge daydreaming ... because we have surplus. For the most part, our hours of daily use remains pretty much static. Agreed ... as a general rule. Exceptions 1) No space to store fuel or generater 2) Periodic maintenance on generater's ICE ... filters, oil, etc ... yuck. 3) Noisier 4) More costly. A commercial UPS cost can be had "on the cheep". It seems AT&T/Verizon etc are quick to upgrade to the latest & greatest UPS setups ... leaving lots of used equipment bargains for those on the prowel. The electrical engineer who set up the PriUPS website has had his UPS grid tied now, for over 4 years ... and it was "years" used when acquired. The sealed lead acid battery used in a commercial grade UPS is pretty robust. Using a commercial UPS in this fashion is atypical. It's not to provide backup power per se, for a house. Rather, it's using the UPS like an intermediary ... like a capaciter ... passing the Prius' 240 DC volts onto the UPS, which then converts it to AC. That's super simplifying it, but plugging your hybrid into the UPS (which then plugs into the house) means the UPS's batteries don't take huge charge/recharg hits ... and that's the reason the the Prius traction pack lasts long, too. You're basically using the Prius as the generater. The hybrid traction pack dips low when powering your house, and then the ICE starts up for a few minutes to recharge the traction pack. Using a hybrid as a generater means you don't have to double up by buying a 2nd generater ... you just have to buy a big UPS. Here's ours: You can see it's like two big ol' computer towers ... that weigh 100's & 100's of pounds. Check out how LOW the Prius sat, hauling it home: Again, the down side. In order to work, and remain charged, it has to be kept plugged in. 200 watts per hour ... 4.7Kwh per 24hr day. THAT's our addition to Jevon. We would be reluctant to go forward with this project ... but for our having over a two thousand Kwh surpluss. Now you know where to come to keep your ice cream frozen, during the next brownout. .