Portable generator hookup cost

Hooking up a portable generator properly costs $600 to $2,000, typically around $1,100. That is a transfer switch or an interlock kit, an inlet box on the outside wall, and the wiring between them.

It is a fraction of the $7,000 to $20,000 a standby generator costs, and it is the answer for most households that lose power a few times a year.

What it costs

Never backfeed

The reason this page exists.

Backfeeding means running a cord from the generator to a dryer outlet or another receptacle to energize the house wiring. It is illegal, it kills utility workers restoring the line, and it can kill you.

With no transfer switch or interlock, power from the generator goes back through the house panel, out to the service drop, and through the utility transformer, which steps it back up to several thousand volts on the line a lineman is working on. It also means that when utility power returns, it arrives at a running generator, which usually destroys the generator and can start a fire.

Two legal ways to do it:

An interlock kit is a sliding metal plate at the panel that makes it physically impossible to have the main breaker and the generator breaker on at the same time. It is the cheapest correct method, $400 to $1,000 fitted, and it lets you use any circuit in the panel, one at a time within the generator's capacity.

A transfer switch is a separate switch, manual or automatic, that disconnects the house from the utility before connecting it to the generator. A manual switch serving six to ten selected circuits is the common residential product.

Both include a power inlet box, a weatherproof outdoor receptacle the generator cord plugs into, so no cable runs through a window.

Sizing it

Add up what you actually need running at once. Starting loads matter more than running loads for anything with a motor.

A 5,000 to 7,000 watt generator covers a fridge, a freezer, a furnace blower, a well or sump pump and lights, which is what most households need. Central air and electric heating are what push you toward a standby unit.

Running it safely

Outdoors only, at least 20 feet from the house, away from windows, doors and vents. Carbon monoxide from a generator in a garage, even with the door open, kills people every winter. Fit CO alarms.

Under cover but ventilated, in a purpose-made canopy rather than a tarp draped over it.

Fuel. Gasoline goes stale in three to six months. Use a stabilizer, rotate the supply, and store it properly. Propane and dual-fuel generators avoid this entirely and are worth the premium for occasional use.

Exercise it. Run it under load for half an hour every three months. A generator that has sat for two years will not start on the night you need it, and that is the most common failure of all.

Frequently asked questions

Interlock or transfer switch?

An interlock is cheaper and gives access to every circuit, with the discipline of managing the load yourself. A transfer switch is simpler to operate and limits you to its selected circuits. Both are correct; the interlock is better value if your panel accepts a listed kit for that brand.

Do I need a permit?

Yes, for either. It is a change to the service arrangement and the inspection is the only check that the utility cannot be backfed.

Can I use an extension cord instead?

Running individual cords to a fridge and a lamp is legitimate and safe, and it is what many households do. It does not power hardwired equipment: the furnace, the well pump, the sump pump. Those are what an inlet and interlock are for.

Is a standby generator worth the extra?

It starts itself, runs on natural gas or propane so there is no fuel to store, and powers the whole house. It costs $7,000 to $20,000 installed. If you lose power for days rather than hours, or someone in the house depends on power, it is a different calculation.

How long can a portable generator run?

Eight to twelve hours on a tank for most, longer for inverter models at partial load. They are not designed to run continuously for days; plan on shutting down to refuel and to let it cool.