My inlaws have had a natural gas Generac for +20 years now and it has been used to run the whole house for 5-8 days in a row several times with absolutely no issues. Depending on natural gas costs it can be expensive - I want to say they were out for 8 days with Super Storm Sandy and I think they used $700 worth of natural gas in those 8 days. It starts automatically once per month, they have it serviced yearly and to my knowledge, it has never failed to start when they needed it. It is not the quietest thing in the world even with the external cover but it's also 20 years old so newer models may be quieter.