What size generator do I need to run my home's essentials?

For most homes, a portable generator in the 5,000 to 8,000 running-watt range covers the essentials people actually want during an outage: the refrigerator, the furnace blower, the well pump, some lights, and the internet. You size for the circuits you want to run at the same time, not for the entire house. If you need a large central air conditioner or an electric range too, you may want more, and we can walk through it.

What is the difference between running watts and starting watts?

Running watts is the steady power a device draws once it is on. Starting watts is the brief surge a motor needs to spin up, often two to three times its running watts. A refrigerator, a well pump, and an air conditioner all surge on startup, so your generator needs enough starting-watt headroom to handle the biggest motor kicking on while everything else is already running.

Do I need a 30-amp or a 50-amp inlet?

It depends on your generator's 240-volt outlet and how much you want to run. A 30-amp inlet supports roughly up to 7,500 watts and pairs with most mid-size portable generators. A 50-amp inlet supports more and suits a larger generator or a home that wants more circuits at once. We match the inlet to your generator and your needs.

Can a portable generator power my entire house at once?

Not all at once, and that is by design. A portable generator powers your selected essential circuits through the panel, not every circuit in the house simultaneously. That is exactly what the inlet and interlock setup is for: you choose which essentials to run. If you truly want automatic backup for every circuit, that is a whole-home standby generator, which is a different and much larger investment.

What Size Generator Do I Need? (Sizing by Circuits, Not Square Feet)

A completed Backup Power Pro generator inlet and interlock install — **Size to the circuits, not the house.** The inlet and interlock let you run your chosen essentials. The generator just needs to cover those, not every breaker at once.

Start with what you actually need on

The mistake is sizing for everything. During an outage you do not need the entire house, you need the handful of things that matter: keep the food cold, keep heat or air moving, keep water running if you are on a well, keep some lights and the internet on. List those, and you have your real load.

Running watts vs starting watts

Every appliance has two numbers, and both matter:

Running watts is the steady draw once it is on.
Starting watts is the brief surge a motor needs to spin up, often two to three times its running watts. Fridges, well pumps, and air conditioners all surge.

You add up the running watts of everything you want on at once, then make sure the generator has enough extra starting-watt headroom for the single biggest motor to kick on while the rest is already running.

Typical essentials and what they pull

These are rough, typical ranges to plan with. Your exact appliances will have their own labels, always check those.

Essential	Running watts (typical)	Surge on start
Refrigerator / freezer	150 to 800	Yes, brief
Furnace blower (gas heat)	600 to 800	Yes
Well pump (1/2 to 1 HP)	1,000 to 2,000	Large, 2 to 3x
Window AC unit	1,000 to 1,500	Yes
Lights (LED, several rooms)	100 to 400	No
Internet + phone charging	50 to 150	No
Sump pump	800 to 1,200	Large

Add up your list, then add headroom for the biggest surge. For most homes the essentials land in the 5,000 to 8,000 running-watt range, which is why generators in that size are the sweet spot.

Bigger is not automatically better. A larger generator burns more fuel, makes more noise, and costs more up front. Size it to your essentials plus a sensible buffer, not to a "just in case" number you will never use. We would rather you buy the right size than the biggest one.

How the inlet size ties in

Your generator's 240-volt outlet and the inlet we install set a ceiling on how much you can pull through one cord:

30-Amp inlet

Supports roughly up to 7,500 watts. Pairs with most mid-size portable generators.

50-Amp inlet

Supports more. Suits a larger generator or running more circuits at once.

We match the inlet to your generator's outlet and to the load you described, so the cord, inlet, and breaker all line up. You are never paying for more than your setup can use.

What the install costs

$1,197 to $1,497

Flat, all-in, for the inlet box + interlock. Permit and inspection included.

Weatherproof inlet box (30A or 50A)
Listed interlock kit for your panel
Generator breaker installed
All wiring, conduit, weatherproofing
The permit and inspection
One-day labor, no return trips

The honest scope

This connects the portable generator you size and own to power your selected essential circuits through your panel. A portable is not meant to run every circuit in the house at once, and that is fine, the whole point is to pick the essentials and keep them on. If you want automatic backup for the entire house, that is a whole-home standby generator, a different and much larger investment we are happy to be honest with you about.

Not sure what your essentials add up to? Tell us what you want to keep running and we will help you match a generator and the right inlet. Read the full inlet and interlock guide, or get your price below.

Get your exact all-in price

Tell us your generator's outlet and we text you your flat price, usually within minutes. No pushy sales.

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My generator has at least one 240-volt, 30-amp or 50-amp outlet.

30-Amp

50-Amp

If your generator has either of these, you qualify. If not, or you're still shopping, reach out once you have a 240V generator and we'll get you connected.

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