Understanding the Power Requirements
Well pumps are an often-overlooked critical load. Homes on well water lose water pressure within minutes of a power outage once the pressure tank empties. A 1 HP submersible well pump is the most common residential size, running at 750–800 watts with a startup surge of 2,100–2,400 watts. Deeper wells with longer pump lifts may require larger pumps and proportionally larger generators.
Well pump wattage by horsepower: 1/2 HP = 500–750W running / 1,500–2,250W surge. 3/4 HP = 650–900W running / 1,950–2,700W surge. 1 HP = 750–1,000W running / 2,250–3,000W surge. 1.5 HP = 1,100–1,400W running / 3,300–4,200W surge. 2 HP = 1,500–1,900W running / 4,500–5,700W surge. Submersible pumps (most common) have different starting characteristics than above-ground jet pumps.
Choosing the Right Generator Size
For a 1 HP well pump alone, a 3,000-watt generator handles the load. Realistically, you need water AND refrigeration AND lights — a 5,000-watt generator covers a well pump, refrigerator, and essential lighting. If you also have a sump pump, budget 7,500 watts.
This appliance surges to 2.3 kW (3× running watts) at startup. Your generator's starting watts — not rated watts — must exceed this. Always verify the generator's peak/surge rating before purchasing.
Wattage Summary
| Specification | Value |
|---|---|
| Running Watts | 750 W |
| Surge Watts | 2.3 kW |
| Minimum Generator | 3 kW |
| Recommended Generator | 5 kW |
Buying Tips
Check your pressure tank — a properly sized tank means the pump only runs every 5–10 minutes, not continuously.
Deep-well submersible pumps (100+ feet) are efficient but need proper surge capacity. Measure your actual pump depth if possible.
A 12V DC backup pump system ($200–$500) can run from a car battery for short outages — good secondary protection.
Some well pump controllers have soft-start capability built in — worth checking if you have a newer installation.
What Else Can Run With It?
Common appliances paired with this load. Combined running load: 2.4 kW. Recommended generator for this combo: 7.5 kW.
| Appliance | Running Watts |
|---|---|
| Well Pump ← this page | 750W |
| Refrigerator | 150W |
| Sump Pump (1/2 HP) | 800W |
| LED Lights | 100W |
| Furnace Blower | 600W |
| Combined Running Total | 2.4 kW |
* Recommended generator for this combination: 7.5 kW (includes 20% safety margin and surge headroom)