What will a 3,500-watt generator run?
A 3,500-watt portable covers the storm-basics list: fridge, freezer, furnace blower, lights and Wi-Fi peak at 2,900W, inside its 4,375W ceiling, and it even squeaks the fridge + furnace + 1/2 HP sump list in at 4,300W. Where it stops is stacked starts: run the microwave and coffee maker with the fridge, or add a 1 HP well pump, and the peak climbs past what it can hold.
The three tables sort common outage load lists by how a 3,500-watt handles each one. Every running and starting figure comes from the same engine the wattage picker and the wattage chart use. "Runs easily" means the list stays under 80% continuous with the start spike covered; "runs with load management" means it fits but you're near the ceiling or staggering starts; "won't run" means the running total or the start spike is over the line. Loads tagged 240V also need a 240V outlet, which starts at the 5,000W class.
Runs easily
| Load list | Running | Peak start |
|---|---|---|
| Lights, Wi-Fi, and phone or laptop chargers | 200 W | 200 W |
| TV, streaming box, Wi-Fi, and lights | 400 W | 400 W |
| A CPAP machine overnight | 60 W | 60 W |
| One 1,500W space heater | 1,500 W | 1,500 W |
| A microwave on its own | 1,400 W | 1,400 W |
| A refrigerator on its own | 700 W | 2,200 W |
| Fridge, freezer, and the keep-alive basics | 1,400 W | 2,900 W |
| Winter storm: fridge, furnace blower, lights, Wi-Fi | 1,700 W | 3,250 W |
| Flooding storm: fridge, furnace, 1/2 HP sump, basics | 2,750 W | 4,300 W |
| Well water: fridge, 1/2 HP well pump, basics | 1,900 W | 3,400 W |
| A 10,000 BTU window AC with fridge and basics | 2,100 W | 3,600 W |
Won't run on this size
| Load list | Running | Peak start |
|---|---|---|
| Kitchen morning: microwave, coffee maker, fridge | 3,100 W | 4,600 W |
| A 1 HP well pump with fridge and furnace 240V | 3,700 W | 5,700 W |
| An electric water heater with fridge and basics 240V | 5,400 W | 6,900 W |
| Central AC (3 ton) with fridge and furnace fan 240V | 5,200 W | 7,700 W |
| An electric dryer 240V | 5,400 W | 6,750 W |
| Level 2 EV charging (40A) 240V | 9,600 W | 9,600 W |
| Central AC, electric dryer, fridge, and furnace together 240V | 10,600 W | 13,100 W |
| Central AC, dryer, and Level 2 EV all at once 240V | 20,000 W | 22,500 W |
How to read these tables for your own list
A 3,500-watt holds about 2,800 watts continuously (80% of its 3,500W rating) and survives a start spike up to 4,375W. Add the running watts of everything you'll have on at once, then add the single largest start surge on top of that total. If both numbers fit, so does the list. The wattage picker does that arithmetic for your exact appliances, and the wattage chart lists the per-appliance numbers behind these lists.
Anything that connects to your electrical panel (a furnace, well pump, central AC, or a whole-house transfer) is licensed-electrician work, wired through a transfer switch or interlock. A generator powers those through that equipment, never by backfeeding an outlet, and it always runs outside, well away from the house.
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Questions people ask
Will a 3,500-watt generator run a furnace and a refrigerator?
Yes, with the storm basics alongside. Fridge + furnace + lights + Wi-Fi runs about 1,700W and peaks at 3,250W, inside the 4,375W ceiling. Add a 1/2 HP sump and it still fits; add the microwave and coffee maker on top of the fridge and it does not.
How many appliances can a generator run at once?
As many as fit two limits at the same time: the running watts have to stay under about 80% of the rating (that is the 3,500W a 3,500-watt holds continuously, so roughly 2,800W of steady load), and the single biggest motor start has to land under the 4,375W peak. Add running watts for everything on, then add the largest one start spike on top. The tables above do that for the common lists.
Running watts or starting watts: which one sizes the generator?
Both, on different clocks. Running watts are what the generator holds for hours, so they set the continuous size; the starting spike is what it has to survive for about a second when the biggest motor kicks in. A unit that clears the running total but not the spike stalls at start; one that clears the spike but runs at 95% all night runs hot and drinks fuel.