Generator Wattage Chart

How to Use This Wattage Chart

This chart is your starting point, not your final answer. Generator wattage planning is all about knowing your actual load — and that requires understanding both the running watts and the starting watts for every appliance you intend to power.

Step 1: List Every Appliance You Need to Run

Start by making a list of every appliance that must stay on during a power outage — or that you need to run on a job site. Prioritize ruthlessly. Do you really need the electric dryer during a two-day outage? Probably not. The refrigerator, sump pump, and a few lights? Absolutely.

The appliances you select determine whether you need a 2,000W inverter generator or a 10,000W open-frame unit. A 3-ton central AC alone needs up to 10,000 starting watts — which immediately rules out every portable generator under $1,500.

Step 2: Add Up Running Watts

Find each appliance in the chart above and note its running watts. Add them all together. This sum is your continuous load — the minimum your generator must sustain without overheating.

Example: Refrigerator (150 W) + Furnace fan (800 W) + TV 55" (100 W) + 10 LED lights (100 W) + phone chargers (20 W) = 1,170 W running.

Step 3: Find Your Peak Starting Watts

Now look at the starting watts for each motor-driven appliance on your list. You don't add all the starting watts together — instead, find the single largest starting surge and add that to your total running watts.

This works because motors don't all start simultaneously. In practice, your furnace fan turns on; 20 minutes later, the refrigerator compressor cycles; an hour later, the sump pump kicks on. Each starting event is isolated.

Using the example above: Furnace fan starting watts = 2,350 W. Surge above running = 2,350 − 800 = 1,550 W extra. Peak starting demand = 1,170 + 1,550 = 2,720 W. A 3,500W generator handles this comfortably.

Step 4: Apply a Safety Margin

Never run a generator at 100% capacity for extended periods. Most manufacturers recommend staying at or below 80% of rated wattage for sustained loads. If your calculation says 3,400 W, a 3,500W generator is technically sufficient but leaves almost no headroom. Go up to 4,000W or 5,000W to run cooler and extend the generator's life.

Why Starting Watts Matter So Much

The starting surge is temporary — typically 2 to 3 seconds — but it's real, and generators that can't supply it will bog down, trip their circuit breaker, or fail to start the motor entirely. A generator that "almost" handles your AC compressor might work on a cool day but fail on a hot one when the compressor is under maximum load.

For appliances with large motors — well pumps, central AC, compressors — always prioritize a generator with a starting watt rating well above what the appliance requires. The chart starting watt figures are averages; some motors in poor condition or with worn capacitors may draw more.

Why Numbers Vary Between Sources

You'll find slightly different watt figures in different charts, and that's normal. A "500W window AC" might actually draw anywhere from 400W to 700W depending on the brand, age, and ambient temperature. The numbers in this chart are calibrated to be realistic mid-range estimates — useful for planning, but not a substitute for reading the yellow EnergyGuide label on your specific appliance.

For critical equipment like well pumps, medical devices, and large HVAC systems, check the nameplate data (usually on a sticker on the back or inside the door panel) for the exact amperage draw. Convert amps to watts with simple math: Watts = Volts × Amps. Most household circuits run at 120V; large appliances like dryers and ranges use 240V.

Inverter vs. Conventional Generators: Does It Matter for Wattage?

Yes and no. Both types are rated in watts and the math above applies to both. The difference is power quality. Inverter generators produce cleaner, more stable power (low THD — total harmonic distortion), which is critical for sensitive electronics: laptops, CPAP machines, modern TVs, and medical equipment. Conventional open-frame generators are fine for motors, heaters, and lights but can damage sensitive electronics over time.

If your load is primarily electronics and small appliances, choose an inverter generator. If you're running heavy motor loads and power tools, a conventional generator offers more wattage per dollar.

Use the Calculator for a Personalized Result

This chart is a reference. For a precise recommendation based on your specific list of appliances, use our free generator size calculator. It does the surge math for you and recommends the right standard generator size, plus links to top-rated models in that wattage range.