Costco has a sale on a Firman dual fuel 7500 watt generator for $499 and I'm thinking about picking one up for hurricane season. It says that it can run at 50% capacity for 12 hours on 8 gallons of gas but nothing about how long it runs on a tank of propane. Does anyone have a dual fuel generator and if so, how long do they run on a tank of propane? Is this a good deal? My neighbor has rigged his generator to power through his panel and run everything in his house except for A/C. Is this doable for this size unit? Thanks for any feedback.