We have a 25kw Gererac whole house generator, natural gas. It is a Mitsubishi 4 cylinder car engine, liquid cooled, with an automatic transfer switch. Have had it 13 years, has been a good unit. The General folks promote an excessive amount of routine maintenance, I think. With some research you can get auto parts oil filter and air cleaner filters. We had an ice storm 16 years ago , and were out of commercial power 11 days, some in our county were out 22 days. During that outage we used a 3500 watt portable unit to power freezer , refrigerator and a few lights. Worked, some days we use what we got......