A generator wattage calculator converts your plug‑in loads into a generator rating you can order by. It adds your running watts, factors in the single largest starting surge, and applies a safety margin. The result: the generator size you actually need.
Continuous power your equipment draws during normal operation — the baseline for any sizing calculation.
The brief extra power a motor‑driven appliance needs at startup — often 3–4× its running watts.
Running watts + single largest surge + 20–25% headroom = the generator capacity you need.
The calculator totals your running watts, adds the single largest starting surge (not all of them — motors rarely start at once), applies a 20–25% safety margin, and adjusts for altitude. The final number is your recommended generator size, expressed in watts or kVA.
Supports single‑phase and three‑phase at both 50 Hz and 60 Hz — so the answer works in your country.
Handles kW/kVA loads with power factor, motor starting method, altitude, and temperature derating.
Every result maps to a real model in our 8–4,000 kVA range, with fuel consumption and runtime included.
Results feed directly into a factory‑direct quotation — no extra steps, no guessing.
Choose Quick Mode for appliance‑based sizing or Advanced Mode for industrial load calculations. Both methods total your running watts, add the single largest starting surge, apply a safety margin, and tell you the generator size you actually need.
Pick the appliances you need to run. The calculator sums running watts, adds the single largest starting surge, and applies your selected safety margin.
Enter your connected load, motor starting method, site conditions, and expansion plans for a complete kW/kVA sizing report.
Use this reference table to estimate your own load list before you touch the calculator. Values are typical running and starting watts for common appliances.
| Appliance | Running Watts | Starting Watts |
|---|---|---|
| Refrigerator / Freezer | 600–700 | 2,200 |
| Window AC (10,000 BTU) | 1,200 | 3,600 |
| Central AC (3-ton) | 1,500–3,500 | 4,500–7,000 |
| Sump Pump (½ HP) | 800–1,050 | 1,300–4,100 |
| Well Pump (1 HP) | 1,000–1,500 | 4,500 |
| Gas Furnace Fan | 600–800 | 1,600–2,350 |
| Electric Water Heater | 4,000–4,500 | 4,000 |
| Clothes Dryer (electric) | 5,400–5,750 | 5,400 |
| Washing Machine | 750–1,150 | 2,250 |
| Dishwasher | 700 | 700 |
| Microwave (1,000 W) | 1,500 | 1,500 |
| Electric Space Heater | 1,500 | 1,500 |
| LED / CFL Lighting (per fixture) | 10–20 | 10–20 |
| RV Roof AC | 1,400–1,600 | 2,900–4,200 |
| Circular Saw | 1,500 | 1,800 |
| Air Compressor (1 HP) | 1,600 | 4,500 |
| Refrigerated Trailer (reefer) | 800–1,200 | 2,000–2,800 |
The honest answer: it depends on your loads, not your square footage. A 2,000 sq ft house with gas heat needs far less power than a 1,600 sq ft house running electric heat and central AC. Size by the appliance list, not the floor plan.
Refrigerator, lights, well or sump pump, furnace fan, and a few outlets for phones and a router. This covers the basics during a short outage — keep food cold, stay warm, and stay connected.
Essentials plus a window AC, microwave, TV, and coffee maker. This keeps life close to normal — you can run a small air conditioner, make a meal, and stay entertained during extended outages.
Central AC, electric water heater, electric dryer, and most of the house. This usually means a standby unit, not a portable set. It's the full solution for homes where losing power means losing comfort.
List what you genuinely need during an outage, count the fridge and AC surge, and run it through the generator wattage calculator. The result will be a defensible figure, not a guess — and it will save you from buying too small or paying for too much.
Size by load, not by floor area. Two homes with the same square footage can have completely different power needs. One might need 4,000 W; the other might need 15,000 W. The only way to know is to add up your actual loads. The calculator above does that in seconds.
Add your appliances, get your running watts and starting surge, and see exactly what size generator you need — for essentials, comfort, or whole-home backup. Then request a factory-direct quote with your results pre-filled.
You’ve calculated your running watts and starting surge. Now let our engineers verify your selection and deliver a factory-direct quote — free of charge. With 25+ years of experience and generator solutions from 8–4,000 kVA, Shandong Huali delivers reliable power worldwide.
A:About 600–700 W running and 2,200 W starting. The surge is the number that matters for sizing, because the compressor draws it every time the fridge cycles on.
A:A 10,000 BTU window unit runs at about 1,200 W but needs roughly 3,600 W to start. If you’re powering a window AC during an outage, size the generator for the surge.
A:It depends on your loads, not the square footage. Essentials-only backup runs 3,000–5,000 W; comfort coverage with window AC and a microwave runs 5,000–7,500 W; whole-home backup with central AC can reach 10,000–20,000 W. Run your list through the calculator for a firm number.
A:A modest RV setup (lights, a fridge, water pump, and charging) runs 1,500–3,000 W. Add a roof AC and you’re looking at 3,500–5,000 W, because the AC pulls a heavy starting surge.
A:No. Add the running watts of everything you’ll run at once, then add the single largest starting surge. Motors rarely all start at the same moment, so adding every surge oversizes the generator needlessly.
A:Watts (kW) are the real power your equipment uses. kVA is the total capacity the generator must supply. They’re connected by the power factor: divide kW by 0.8 to get kVA. Our watts to kVA calculator converts for you instantly.
A:Yes. We offer OEM/ODM customization across our full 8–4,000 kVA range. If your calculated size or configuration doesn’t match a standard model, our engineering team builds the unit to your specification (voltage, frequency, enclosure, control system, and more).
