What Size Generator Do You Need for a Hot Tub?
Quick answer
To run a hot tub (240V spa) alone, a generator needs at least 7,000 running watts and 7,500 starting watts. A typical 240V hot tub draws about 7,000 running watts with the heater (about 5,500 W) and pumps on together, and needs roughly 7,500 starting watts - mostly resistive load, so the surge is modest. Smaller 120V plug-and-play tubs draw far less (about 1,500 W) but heat slowly. These are typical values; your spa's nameplate states its actual draw.
Running it on a portable
Portable generators in our dataset that clear both numbers on their own:
| Model | Running watts | Starting watts | Approx. price |
|---|---|---|---|
| DuroMax XP13000EH | 10,500 | 13,000 | Around $1,299 |
Running it in a whole-home system
In a whole-home outage load list - the hot tub (240V spa) plus about 3,225 W of household essentials - the combined math lands in the 13 kW standby class with standard headroom. Standby units in that class from our dataset:
| Model | Output | Approx. unit price | Warranty |
|---|---|---|---|
| Cummins QuietConnect 13kW (RS13A) | 13 kW | Around $4,300 | 5-year |
Honest framing: most people let the hot tub sit out an outage - it holds heat for many hours with the cover on. Sizing a whole standby system around the tub usually adds a full size class. If keeping it hot matters (freeze protection in a northern winter is the real case), count it at full draw and expect the 18 kW class or load management.
A note on climate
The math above assumes a mixed climate. Two adjustments matter at the extremes, and both are rules of thumb, not measurements. In a cold climate, heating dominates: the furnace blower runs near-continuously, and if the house has a heat pump with electric auxiliary heat strips (typically 5-15 kW), those strips are the single biggest sizing load in the house when they engage - count them at full draw or use load management to shed them. In a hot climate, the air conditioner is the dominant load and runs near-continuously through a heat-wave outage, so installers commonly add roughly 10% extra headroom on top of the standard margin. Our generator size calculator applies both adjustments openly - you can see exactly what changed.
FAQ
What happens if the generator is too small for the surge?
The voltage sags when the motor tries to start. Motors hum, overheat, or fail to start; electronics on the same circuit may reset; the generator's breaker may trip. Repeated failed starts are hard on both the motor and the generator - undersizing is the expensive kind of cheap.
Do I need to count this load if I have load management?
Load management lets a smaller generator carry a bigger list by shedding selected loads in priority order. It works well for deferrable loads (water heater, dryer, EV charger) and poorly for loads you truly need the moment they call (a sump pump during a storm).