How Much Does It Cost to Run a Hot Tub?
A built-in hot tub with a 240V heater (about 3,000W combined with the pump) running at a 30% heater duty cycle costs roughly $1.20-$1.70 per day, or about $36-$50 per month, at the U.S. average electricity rate of 13-16¢/kWh. An inflatable hot tub with a smaller 120V heater typically costs $0.35-$1.00 per day, or $10-$30 per month — noticeably less in most conditions, though the gap narrows in cold climates.
Unlike most appliances, a hot tub's electricity use isn't just about wattage — it's about how often the heater has to fight heat loss. A well-insulated, well-covered spa in a mild climate might run its heater 15-20% of the time. The same spa in a cold, windy location with a worn-out cover could run 50% or more of the time just to hold temperature, roughly doubling or tripling the electricity cost with the exact same equipment.
Inflatable vs Built-In Hot Tub: Running Cost Comparison
| Inflatable / Portable | Built-In / Hard-Shell | |
|---|---|---|
| Typical heater voltage | 120V | 120V (small) or 240V (large) |
| Typical combined wattage | 1,300–1,500W | 1,500–4,500W+ |
| Insulation | Thin vinyl walls, loses heat faster | Rigid shell, foam-insulated |
| Typical monthly cost (mild climate) | $10–$25 | $30–$50 |
| Typical monthly cost (cold climate) | $40–$80+ | $50–$90 |
| Water volume | 150–250 gallons | 300–500 gallons |
The key takeaway: an inflatable hot tub costs less to run in mild weather because it heats less water with a smaller heater. But in cold climates its thinner walls can cause it to lose the cost advantage — or even become more expensive per month than a well-insulated built-in spa, since it has to run its heater far more often to fight ambient heat loss.
What Affects Hot Tub Running Cost
- Cover quality: A thick, well-fitting, waterlogged-free cover is the single biggest factor in heater duty cycle. A worn-out or ill-fitting cover can double heating costs.
- Set temperature: Each degree above 100°F (38°C) meaningfully increases heater runtime. Dropping the set point 2-4°F when not in use saves noticeably over a month.
- Ambient temperature and wind: Cold, windy locations force the heater to run far more often than sheltered, mild-climate placements.
- Pump run schedule: Some spas run the filtration pump continuously; others cycle it a few hours a day. Continuous pump operation adds a steady baseline cost even when the heater isn't active.
- Insulation quality: Full-foam insulated built-in spas retain heat far better than partially insulated or inflatable models, cutting heater duty cycle substantially.
Tips to Lower Hot Tub Running Cost
- Use a high-quality, well-fitting cover every time the tub isn't in use — this is the highest-impact change you can make.
- Add a thermal blanket (a floating layer under the cover) for inflatable hot tubs, which lose heat fastest through their thin walls.
- Lower the set temperature slightly during periods of lower use, and raise it an hour or two before you plan to use the tub.
- Shelter the tub from wind with a windbreak, gazebo, or enclosure — wind chill significantly increases heat loss on exposed spas.
- Run the pump on a schedule rather than continuously if your model allows it, and check manufacturer guidance for minimum filtration needs.
- Consider running during off-peak hours if your utility offers time-of-use electricity rates.
For related running-cost calculators, see our Pool Pump Running Cost Calculator or Appliance Energy Cost Calculator.