How to Choose a Generator for Home | Match Watts To Needs

Power goes out, and suddenly you’re weighing comfort against cost. The right backup power plan for your home comes down to four decisions made in order: what you need to run, how long outages typically last, which fuel you can keep on hand, and whether portable, inverter, or standby backup fits your situation. A typical home needs around 5,000 watts, according to Consumer Reports, while basics like heat and a few lights often fit in 3,000–5,000 watts. The five-step process below builds your exact number from your actual appliances.

Step 1: List What You Need To Power

Start with paper or a notes app. Walk through the house and write down every appliance and system you’d want on simultaneously. Essentials usually include the refrigerator, sump pump, heating system, lights, and well pump if you have one. Comfort extras—window air conditioner, portable heater, computer—go on a second list you can skip when fuel runs low.

For each item, check the data plate or manual for two numbers:

• Running watts — what the device draws to stay on.
• Starting watts — the short surge motor-driven appliances need at startup. For these, the guideline is running watts x 3, then add that to the running total.

Rough starting points: a refrigerator runs about 600 W, a sump pump 750–1,500 W, a portable heater 1,500 W, a window air conditioner 1,000 W, each light bulb 5–80 W, and a computer 60–300 W. These vary by model, so the label always wins.

Step 2: Add Watts And A Safety Margin

Add the running watts for everything you’ll run at once, then add starting watts for any motorized items that kick on during that window. The total is your minimum. Consumer Reports and others recommend buying roughly 10–20% above your calculated demand, so a 5,000-watt calculated need points to a 5,500–6,000-watt generator.

This margin matters because motors surge when they start. A fridge that runs at 600 W can draw more than 1,800 W for a split second on startup, and if that moment hits while the sump pump is kicking on, an undersized generator stalls or trips.

Step 3: Choose Portable, Inverter, Or Standby

The size you need and the comfort you want decide the type. Homeowners wanting only heat and a few lights usually do fine with a portable generator. Those wanting whole-home power should look at an automatic standby unit wired into the house.

Three main categories:

• Portable generators run on gasoline, propane, or dual fuel, cost about $1,000–$1,500, and need to be wheeled out and connected with extension cords each outage.
• Inverter generators are also portable but produce cleaner power with lower noise and better fuel economy—worth it when powering sensitive electronics like computers.
• Standby generators connect through a transfer switch, start automatically, run on natural gas or propane, and cost roughly $3,500–$7,000 installed.

Step 4: Sort Out Fuel And The 240-Volt Question

The first thing to decide is how you plan to fuel the generator, then how many watts it must carry. Gasoline is cheap and easy but goes stale and runs out during long outages. Propane stores indefinitely. Natural gas never needs refilling but requires a standby installation and pipe capacity. If you expect multi-day outages, check how long each unit runs on a full tank—the spec that matters most after watts.

If you need to power 240-volt appliances like a well pump, electric water heater, or central AC, you need a generator with at least a 30-amp/240-volt output and, for whole-home backup, a transfer switch installed by an electrician. A transfer switch is required for whole-home or any 240V setups; it prevents backfeeding, which can kill a lineman and damage the generator.

Step 5: Weigh The Practical Factors

Beyond watts, size and storage space, noise, price, runtime, and features decide the final pick. Look for automatic starts on standby units, wheels and an economy mode on portables, and enough outlets to run your cords without adapters. Monthly runs, manufacturer-scheduled service, and stabilized fuel or an empty tank keep the generator ready when an outage hits.

Safety first: never run a fuel-based generator indoors. Use outdoor-rated extension cords.

If you’re ready to compare specific tested electrical generators for home backup, our hands-on roundup lines up the top picks by watts, fuel type, and noise. For a quick estimate, Consumer Reports’ generator sizing guidance walks through the same wattage math with appliance examples.