Standby generators. Episode seventy-six of the Gas Service Animated series.

The fastest-growing gas appliance in America sits on a pad beside the house and runs eight days a year — and it draws more gas than the furnace and water heater combined. Standby generators are a sizing story, a placement story, and a pressure story. Miss any of the three and it fails on the exact day it exists for.

Start with the appetite. A typical twenty-two-kilowatt air-cooled unit burns about two hundred twenty-eight cubic feet an hour at half load — and three hundred twenty-seven at full load. That's over three hundred thousand Btu: roughly a furnace, a water heater, a range, and a dryer, running at once, in one machine. Smaller units are gentler but still big: a fourteen-kilowatt pulls around two-fifty at full song.

Now the trap, squared. The pipe run to the pad is sized at full load by longest-length — and pad placement means long runs, so twenty-plus-kilowatt units routinely want inch-and-a-quarter pipe. But the pipe is only half: the meter and service regulator were sized for the house before the generator existed. A standard residential meter often cannot carry the house plus the generator — and that's a utility upgrade conversation, not a bigger pipe. Total the whole load, then check the meter's badge before you run an inch of pipe.

The spec that decides everything: fuel pressure at the generator inlet — typically three-and-a-half to seven inches of water column on natural gas, ten to twelve on propane vapor — at all loads. That means measured dynamic: during crank, during transfer, at full electrical load, with the house appliances running too. A static reading that looks perfect can collapse at crank and drop the unit offline in the first storm minute.

Know the derates. The same unit makes less power on natural gas than on propane — a twenty-two on propane is roughly nineteen-and-a-half on natural. Altitude trims about three-and-a-half percent per thousand feet; heat trims about one percent per ten degrees over sixty. The nameplate is a ceiling with conditions.

Placement is a life-safety code of its own. The engine standard wants outdoor units at least five feet from openings — doors, windows, intakes — and listed residential units are allowed closer to the wall itself per their listing, commonly around eighteen inches, but never closer to openings. The exhaust is an engine's exhaust: the carbon-monoxide season applies in full, and a generator running under a bedroom window is an incident with a schedule.

On propane, the appetite meets the tank physics from the LP season: nearly four gallons an hour at full load is a serious vapor draw, and a small or low tank in cold weather will frost and starve exactly when the outage hits. Size the tank to the generator's full-load draw at winter design — the wetted-surface math, with the power out.

Generators self-test — a five-to-twelve-minute exercise weekly, biweekly, or monthly. That's a routine gas draw the piping already handles if it was sized right, and a routine noise the customer should expect. An exercise that fails is the system telling you about fuel pressure or ignition on a calm day — read it as the storm-day rehearsal it is.

Generators in one breath. Three hundred-plus cubic feet at full load. Size the pipe at full load, then check the meter can carry the whole house plus the machine. Prove pressure dynamic, through crank. Respect the derates, the five-foot rule, and the exhaust. And listen to the exercise. Next: the future of the fuel itself.