Backup power FAQ

Total the running watts of everything you need on at the same time, add only the single largest additional start-up surge, then divide the running total by 0.8 for continuous-running headroom. Most houses land between 3,000 and 7,500 running watts. Our load calculator does this with published figures in about two minutes.

Just the biggest one. Both published charts we cite specify adding only the single largest additional surge to the running total, because motors do not all start in the same instant. Adding every surge can easily double the figure and is the most common sizing error.

The Eugene Water & Electric Board chart lists a refrigerator or freezer at 700 running watts; Champion lists a refrigerator at 400. Both agree on a 2,200 watt additional surge to start the compressor, and that surge is usually the largest single number in a whole outage plan.

Only its blower, igniter and controls — EWEB puts a 1/3 HP furnace fan blower at 700 running watts with a 1,400 watt additional surge. That is the best news in home backup: during an outage the gas is still flowing and all that is missing is a few hundred watts.

No. An oversized generator costs more, burns more fuel at light load, is heavier and louder, and often cannot deliver its extra capacity anyway — a 30 amp transfer switch caps throughput at about 7,200 watts regardless of the engine.

Usually yes, and not for the reason normally given. It is not cheaper to run — propane carries fewer BTU per gallon. It is worth it because propane stores indefinitely while gasoline degrades within months, and stale fuel is the most common reason a stored generator will not start.

About 10%, remarkably consistently. Every machine that publishes both fuels lands within a point of it: Westinghouse's WGen9500DF goes from 9,500 to 8,500 running watts, Champion's 11,500 W from 9,200 to 8,280.

15 to 25%. Champion's 12,500 W tri-fuel drops from 10,000 running watts on gasoline to 8,000 on natural gas; WEN's TF-1450X from 11,500 to 8,750. If gas is your primary fuel, that lower figure is your sizing number.

Only if a natural gas connection is realistic at your house. If it is, a plumbed supply removes refueling from your plan entirely, which is the single most consequential feature in a multi-day outage. Without a gas supply the third fuel is capability you will never use.

You need one — or an interlock kit — to power hard-wired loads like a furnace, well pump or sump pump, because there is no plug to run a cord to. For individual plug-in appliances a cord is fine. Back-feeding through a dryer outlet is never an acceptable alternative.

Yes. Both make simultaneous utility and generator connection mechanically impossible, and Eaton's own interlock kit states that it meets National Electrical Code Article 702 requirements. The differences are cost, circuit access and who manages the load — not safety.

Match it to your generator. A 30 amp switch passes about 7,200 watts at 240 volts; Reliance states a 7,500 maximum running watt ceiling for its 30 amp kit. Above that you need 50 amps, which raises the cost of the cord, inlet and conductors too.

In most US jurisdictions, no. It is permanent wiring on the supply side of your panel, which is licensed work requiring a permit and an inspection. This site covers what to buy; your electrician installs it.

For a 30 amp connection, 10 AWG four-conductor with L14-30 twist-locks at both ends. At least 25 feet, because CPSC guidance puts the generator 20 feet from the house. Note that L14-30 and L5-30 look similar and are not interchangeable.

At least 20 feet, per CPSC guidance, outdoors, with the exhaust pointed away from doors, windows and vents. Never in a garage, basement or crawlspace, even with the door open — carbon monoxide accumulates faster than an opening clears it.

Yes. The generator's shutoff monitors its own operating area, not your house. You need battery-powered CO alarms indoors on every sleeping level — and battery-powered specifically, because a plug-in alarm is dead during the outage you bought the generator for.

Yes, with a purpose-made running cover that sheds water away from the electrical components while leaving the exhaust and air intake fully open. Not under a tarp, and never by moving it into a garage or shed — those are enclosures.

A battery is better for small loads, short outages and anyone needing to run indoors or quietly. A generator is better for motor loads like well pumps and for multi-day outages. The surge requirement of your largest load usually decides it.

Roughly 15-20 hours for a 1 kWh unit and 30-40 hours for a 2 kWh one, on our arithmetic at 88% inverter efficiency and an assumed cycling average. Check the surge rating too — you need about 3,000 watts to start a compressor.

It depends on your load, your machine's consumption and your local fuel price, so any single figure would be a guess. Our fuel cost calculator takes your numbers and shows the arithmetic. The key insight: consumption tracks load closely — one machine publishes 14 hours at quarter load and 9.5 at half load from the same tank.