Generator sizing
Generator Wattage Chart 2026: Running + Starting Watts for 50+ Appliances (NEC 702)
Wattage chart + calculator Based on NEC 702 (NFPA 70) & manufacturer specs Reviewed by the WhatSize editorial team
Last reviewed June 2026 • Sources: NEC 702, DOE Energy Use Chart, manufacturer spec sheets (Generac, Honda, Champion)
Quick answer
Generator size = your appliances’ total running watts × 1.25 + the largest single starting surge. A typical 2,000 sq ft home needing fridge, sump pump, furnace blower, and lights requires a 5,000–7,500 watt generator. Use the chart below to add up your appliances, then use our free calculator to get an exact size in 60 seconds.
Appliance Wattage Chart: Running & Starting Watts
All figures are typical for modern US appliances. Starting watts (surge) are 2–7× running watts for motors; resistive loads (heaters, lights) have no surge.
| Appliance | Running W | Starting W | Notes |
|---|---|---|---|
| Refrigerators & Freezers | |||
| Refrigerator/freezer (20 cu ft) | 150–200 | 600–800 | Surge 3–4× running |
| Chest freezer (15 cu ft) | 100–150 | 500–700 | |
| Side-by-side fridge w/ ice maker | 200–250 | 800–1,200 | |
| Sump & Well Pumps | |||
| Sump pump 1/3 HP | 400–500 | 1,200 | |
| Sump pump 1/2 HP | 800–1,000 | 2,100 | |
| Sump pump 3/4 HP | 1,100–1,500 | 2,800 | |
| Well pump 1/2 HP | 1,000 | 2,000 | |
| Well pump 1 HP | 2,000 | 4,000 | |
| Heating & Cooling | |||
| Furnace blower 1/3 HP | 600–800 | 1,200–1,500 | |
| Central AC 2.5 ton | 3,500 | 7,000 | Surge 2× running |
| Central AC 3 ton | 3,500–4,000 | 7,000–8,000 | |
| Central AC 5 ton | 6,000 | 12,000 | |
| Window AC 6,000 BTU | 600–750 | 1,200–1,500 | |
| Window AC 10,000 BTU | 1,200–1,500 | 2,400–3,000 | |
| Major Appliances | |||
| Electric water heater (50 gal) | 4,500 | — | Resistive, no surge |
| Electric dryer | 5,400 | — | Resistive, no surge |
| Electric stove (per burner) | 1,500 | — | |
| Microwave oven | 1,000 | — | |
| Dishwasher | 1,200 | — | |
| Washing machine | 500 | 1,500 | |
| Electronics & Lighting | |||
| LED lights (10 bulbs) | 100 | — | |
| TV (50″ LED) | 100 | — | |
| Desktop computer + monitor | 200–400 | — | |
| WiFi router + modem | 10–20 | — | |
| CPAP / medical device | 60–150 | — | |
How to Calculate Generator Size: The NEC 702 Formula
Total Required Watts = (Σ Running Watts × 1.25) + Largest Single Starting Surge
Add up running watts of all appliances you want to power simultaneously.
Multiply by 1.25 — the NEC 210.20(A) continuous-load margin for circuits expected to run 3+ hours.
Add the largest single starting surge — only ONE motor starts at a time. NEC 702 doesn’t require summing all surges.
NEC 701 vs NEC 702: Which Applies to Your Generator?
You may see both “NEC 701” and “NEC 702” cited in generator sizing guides. Here’s the difference:
NEC Article 701
Legally Required Standby Systems. Applies to hospitals, fire pumps, elevators, sewage treatment — systems that must run by law during outages. Requires automatic transfer switch. Not applicable to typical residential generators.
NEC Article 702 — Residential Standard
Optional Standby Systems. This is the code that applies to your home generator. Covers portable and standby generators used voluntarily during outages. All wattage recommendations on this page follow Article 702.
Generator Size Guide: What Each Wattage Tier Can Run
| Generator Size | Can Run | Best For | Typical Price |
|---|---|---|---|
| 2,000–3,500W | Fridge, lights, phone charger, 1-2 small appliances | Camping, RV, short outages | $400–$800 |
| 5,000–7,500W | Fridge, sump pump, furnace blower, lights, window AC | Home essentials backup | $800–$1,500 |
| 10,000–15,000W | Most home circuits, well pump, central AC (with soft start) | Whole-home portable | $1,500–$3,000 |
| 20,000–26,000W | Entire home including central AC, electric appliances | Whole-home standby | $5,000–$12,000 installed |
Best Generators by Size: Our Top Picks
Each pick is verified to meet or exceed the NEC 702 wattage requirements. We sort by specs, not commission. Read our product policy.
Best Portable Generators
Best Standby Generators
Disclosure: WhatSize Appliance earns a commission when you buy through Amazon links. This doesn’t affect which products we recommend. Read our full disclosure.
Generator Wattage FAQ
What’s the difference between running watts and starting watts?
Running watts (rated watts) is the continuous power a device draws while operating. Starting watts (surge watts) is the short burst needed to start motors — typically 2–7× running watts, lasting 2–3 seconds. Always size your generator for the running total plus the largest single starting surge.
What size generator do I need for my house?
For essential circuits (fridge, sump pump, furnace, lights): 5,000–7,500 watts. For most of a 2,000 sq ft home including window AC: 7,500–10,000 watts. Whole-home including central AC: 20,000–26,000 watts (standby). Use our free calculator for your exact number.
Do I add ALL starting surges together?
No. NEC 702 practice is to add only the largest single starting surge to the total running watts. Multiple motors don’t start simultaneously in normal operation. Adding all surges together would unnecessarily oversize your generator.
Portable vs standby generator — which should I choose?
Portable ($400–$3,000): manual setup, runs on gas/propane, powers select circuits via extension cords or transfer switch. Standby ($5,000–$12,000 installed): auto-start within seconds, runs on natural gas/propane, powers entire home. See our full portable vs standby comparison.
Get Your Exact Generator Size in 60 Seconds
Check off what you need to power and our NEC 702-based calculator gives you the exact wattage — plus the best generator to buy.
Try the Generator Calculator