Running Watts vs. Startup (Surge) Watts Explained
Every appliance has two different wattage figures that matter for generator sizing:
The steady-state power draw while the appliance operates normally. This is what your generator must supply continuously. Also called "rated watts" or "continuous watts."
A brief power spike when an electric motor starts. Can last less than 1 second but reaches 3–6× the running wattage. Your generator must handle this spike or it will stall.
Only appliances with electric motors produce a startup surge. Resistive loads (toasters, incandescent bulbs, space heaters) have no surge — their startup watts equal their running watts.
When sizing a generator, add all running watts together, then add the surge delta (startup minus running) of your single largest motor. This is your peak load. Apply a 20% buffer. Use our Generator Size Calculator which handles this math automatically.
🌡️ HVAC & Cooling
| Appliance | Running Watts | Startup Surge | Notes |
|---|---|---|---|
| Central A/C — 1.5 ton | 1,800W | 5,400W | Startup is ~3× running |
| Central A/C — 2 ton | 2,800W | 8,000W | Most common residential unit |
| Central A/C — 3 ton | 3,800W | 9,800W | High surge; requires large generator |
| Central A/C — 4 ton | 5,000W | 12,000W | Needs standby generator |
| Window A/C — 5,000 BTU | 500W | 1,500W | Small bedroom unit |
| Window A/C — 10,000 BTU | 900W | 2,700W | Living room / large bedroom |
| Window A/C — 14,000 BTU | 1,400W | 3,800W | Large room unit |
| Portable A/C | 1,000–1,400W | 2,800W | Less efficient than window units |
| Furnace Fan (gas furnace) | 400–900W | 2,000W | Fan only; burner is gas |
| Heat Pump — 2 ton | 2,200W | 7,200W | Dual use: heating and cooling |
| Electric Space Heater 1,500W | 1,500W | 1,500W | No motor = no surge |
| Whole-House Fan | 300–500W | 1,200W | Attic venting only |
| Ceiling Fan | 10–75W | 75W | Negligible load |
| Box Fan / Tower Fan | 40–200W | 400W | Low surge |
🏠 Essential Appliances
| Appliance | Running Watts | Startup Surge | Notes |
|---|---|---|---|
| Refrigerator (full-size) | 150–400W | 800–1,200W | Cycles on and off; use peak for sizing |
| Chest Freezer | 100–200W | 600W | Very efficient per cubic foot |
| Sump Pump — ½ HP | 800W | 2,150W | Critical during storms; high surge |
| Sump Pump — 1 HP | 1,500W | 3,900W | Larger basement sump |
| Well Pump — ½ HP | 900W | 2,500W | Rural homes; high priority load |
| Well Pump — 1 HP | 2,000W | 5,000W | Requires large generator |
| Oxygen Concentrator (5 LPM) | 300W | 600W | Medical — always verify amp draw on label |
| CPAP Machine | 30–60W | 60W | No surge; some include battery backup |
| Home Security System | 15–40W | 40W | Negligible |
| Garage Door Opener (½ HP) | 350W | 875W | Brief run cycles only |
| Sewer Ejector Pump | 800W | 2,200W | Basement bathroom ejector |
🍳 Kitchen Appliances
| Appliance | Running Watts | Startup Surge | Notes |
|---|---|---|---|
| Microwave (1,000W) | 1,000–1,500W | 1,500W | Resistive; no motor surge |
| Coffee Maker | 600–1,200W | 1,200W | Short brew cycle |
| Toaster | 1,000–1,500W | 1,500W | Resistive; no surge |
| Electric Kettle | 1,200–1,500W | 1,500W | Short 2–3 min cycle |
| Refrigerator compressor startup | 150–400W | 800–1,200W | See Essential Appliances above |
| Dishwasher | 1,200–1,800W | 1,800W | Mostly resistive heating; low surge |
| Food Processor | 400–1,000W | 1,400W | Motor load; moderate surge |
| Stand Mixer | 300–575W | 1,200W | Motor startup surge |
| Blender | 300–800W | 1,500W | High-power blenders draw more |
| Electric Stove (single burner) | 1,500W | 1,500W | Resistive; no surge |
| Electric Stove (full range) | 5,000–8,000W | 8,000W | 240V; needs large generator or skip |
| Slow Cooker / Instant Pot | 150–1,000W | 1,000W | Efficient low wattage option |
💻 Electronics & Office
| Appliance | Running Watts | Startup Surge | Notes |
|---|---|---|---|
| Laptop Computer | 45–100W | 100W | Negligible load |
| Desktop Computer + Monitor | 150–400W | 500W | Gaming PCs can reach 500–800W |
| WiFi Router | 5–20W | 20W | Very low; keep on |
| Smart TV (50") | 70–150W | 150W | Modern LCDs are very efficient |
| Phone / Tablet Charger | 5–20W each | 20W | Budget 50–100W for all devices |
| Cable DVR / Set-Top Box | 15–50W | 50W | Low continuous draw |
| Gaming Console | 100–200W | 200W | Non-essential; skip during outage |
| Inkjet Printer | 30–50W | 50W | Negligible |
| Laser Printer | 400–600W | 1,000W | Fusing element is high draw |
💧 Laundry & Water Heating
| Appliance | Running Watts | Startup Surge | Notes |
|---|---|---|---|
| Washing Machine | 500–1,000W | 2,250W | Motor surge; hot water adds load |
| Electric Clothes Dryer | 5,000–6,000W | 6,000W | 240V; skip during outages if possible |
| Gas Clothes Dryer | 300–700W | 1,800W | Motor only; burner is gas |
| Electric Water Heater (40 gal) | 4,000–5,500W | 5,500W | 240V high draw; skip during outages |
| Tankless Water Heater (electric) | 7,000–27,000W | 27,000W | 240V; very high demand — not practical on generator |
| Portable Washing Machine | 200–500W | 1,000W | Countertop or compact unit |
🔧 Power Tools & Workshop
| Appliance | Running Watts | Startup Surge | Notes |
|---|---|---|---|
| Circular Saw (7¼") | 1,400W | 2,800W | High startup; don't run simultaneously with other loads |
| Electric Drill | 400–800W | 1,800W | Surge on hard starts |
| Shop Vacuum | 750–1,200W | 2,400W | Motor surge on startup |
| Air Compressor (1 HP) | 1,000W | 3,000W | Very high surge; size carefully |
| Air Compressor (2 HP) | 1,800W | 5,400W | Requires dedicated large generator |
| Angle Grinder | 900–1,800W | 3,000W | High surge on startup |
| Table Saw (10") | 1,800W | 4,500W | Very large motor surge |
| Battery Charger (car) | 50–200W | 300W | Low load; leave running during outage |
| EV Vehicle Charger (Level 1) | 1,400W | 1,800W | 120V standard outlet; slow but works on generator |
💡 Lighting
| Bulb Type | Running Watts | Startup Surge | Notes |
|---|---|---|---|
| LED Bulb (60W replacement) | 8–10W | 10W | Best choice for generator use |
| LED Bulb (100W replacement) | 13–16W | 16W | Very efficient |
| CFL Bulb (60W replacement) | 14W | 14W | Being phased out; fine if already installed |
| Incandescent Bulb (60W) | 60W | 60W | Replace with LEDs before next outage |
| LED Strip (per 16 ft roll) | 30–50W | 50W | Efficient accent / emergency lighting |
| Outdoor Flood Light (LED) | 50–100W | 100W | Security lighting |
Practical Tips for Reading Appliance Labels
Most appliances have a label — usually on the back, bottom, or inside the door — that lists electrical specifications. Here's how to read them:
- Watts (W): Already in the unit you need. Use this directly.
- Amps (A) at 120V: Multiply by 120 to get watts. Example: 8.5A × 120V = 1,020W.
- Amps (A) at 240V: Multiply by 240. Example: 24A × 240V = 5,760W.
- HP (horsepower): Multiply by 746 to get running watts. A ½ HP motor = 373W running. The startup surge is typically 2.5–3× this.
- BTU (air conditioners): Divide by 10 to get approximate watts. A 12,000 BTU unit ≈ 1,200W running.
Can't find a wattage label? Search "[appliance brand + model] wattage" or check the manufacturer's spec page. For the most accurate figures, use a Kill A Watt meter (about $25) to measure actual draw before a storm season begins.
Frequently Asked Questions
A full-size refrigerator draws 150–400W while the compressor runs. However, the compressor starts and stops throughout the day — it doesn't run continuously. For generator sizing, you must account for the startup surge of 800–1,200W. Modern Energy Star refrigerators are at the lower end; older units can exceed 400W running.
A 10,000 BTU window A/C draws about 900W running with a startup surge near 2,700W. A 5,000 BTU unit runs at ~500W (1,500W surge). Rule of thumb: watts ≈ BTU ÷ 10. Always size your generator using the startup surge figure, not the running watts.
The highest continuous draws are: central air conditioning (2,800–5,000W), electric water heater (4,000–5,500W), electric dryer (5,000–6,000W), and electric range (5,000–8,000W). For generator purposes, skip the water heater and electric dryer/range unless you have a large standby generator. Focus on HVAC, refrigeration, lights, and pumps.
Yes, for motor-driven appliances. A well pump motor draws more current pumping against higher head pressure. A refrigerator compressor draws more in a hot kitchen than a cool basement. The wattage values in this guide represent typical operating conditions. When in doubt, add 10–15% to the running wattage shown for safety margin.
Ready to size your generator?
Use these wattage figures in our interactive calculator. Add appliances, get a recommendation in seconds.