The classic storm pair
Food and a dry basement are what most people want first in a storm outage.[1] Both appliances cycle by themselves and both have compressor or motor surges, so both run “together”.
They won’t start in the same second, so only the larger of the two startup jumps — usually the fridge’s — is added on top of both running loads.
Getting through a storm with both running
In heavy rain the sump pump can cycle every few minutes, so expect it to start at any moment — including while the fridge compressor is starting. The starting-watts number is sized for exactly that worst moment.
A closed fridge keeps food cold for about 4 hours without power[2], so there is time to set the generator up safely outdoors before the pit fills. Keep the door shut until power is back.
If the generator might run out of fuel overnight, a battery backup pump that takes over when the main pump fails is a good second line of defense.[3]
How the number adds up
| Appliance | Running | Starting | Runs |
|---|---|---|---|
| Refrigerator | 700 W | 2,900 W | together |
| Sump pump (1/2 HP) | 1,050 W | 2,700 W | together |
| Running load | 1,750 W | everything together + the biggest “takes turns” item | |
| Worst startup moment | 3,950 W | running load + Refrigerator starting (+2,200 W) | |
| Minimum generator | 2,188 W | rated watts (running ÷ 0.8) · how we size | |
Questions
Can I add lights and Wi-Fi?
Yes — LED lights, a router and phone chargers add very little. Try the Essentials preset in the calculator.
Do I need a transfer switch for this pair?
Not if both plug in — run a heavy-duty outdoor extension cord to each. A hardwired sump pump needs a transfer switch or interlock installed by a qualified electrician.[4]
What if I also have a chest freezer?
Add it in the calculator. A freezer cycles on its own like the fridge, so it runs together with the others — but the compressors and the pump rarely start in the same second, so only the biggest startup jump is added on top.