The Real Cost of Running a Hot Tub
Introduction
Ever wondered how much it truly costs to run a hot tub? As a lodge owner, and an engineer, I decided to find out by monitoring the energy consumption of my hot tub. Using a separate energy meter, I tracked consumption and also recorded lodge occupancy and ambient temperature. The results were both eye-opening and useful for reducing costs and environmental impact. At the same time, I ran a few tests on lodge temperature settings. Important to note that my goal was to look at what can be done when the lodge is unoccupied since when guests are present, they will of course make their own decisions on temperature settings etc.
Gas Consumption and Lodge Temperature Management
In 2022, I installed a Hive thermostat to control my lodge’s temperature. This allowed me to answer two important questions:
- What is the minimum temperature a lodge should be maintained at for frost protection?
- How long does it take to raise the temperature to a comfortable level for guests?
The Hive default frost protection temperature is 7°C, which prevents frozen pipes without unnecessary heating costs. However, to help prevent damp or condensation, I maintain my lodge at 10°C when unoccupied. This setting also aligns with recommendations in a recent Sunday Times article.
Testing showed that increasing the lodge temperature from 10°C to 20°C took about 4 hours when the ambient temperature was 7°C —ample time to ensure comfort for guests arriving at 4 PM. As a result, my gas consumption dropped significantly, from 443 units in 2021 to 217 units in 2023—a 51% reduction, saving approximately £365 annually at the then current prices.
Electricity Consumption: Hot Tub Insights
Hot tubs are a luxury, but they can also be an energy guzzler. My energy monitoring project began in June 2023, aiming to answer these key questions:
- How much energy does my hot tub use?
- How does usage vary when the temperature is reduced during non-occupancy?
- How long does it take to heat the tub back to normal levels?
- Are there chemical effectiveness issues at lower temperatures?
In the year ending October 2023, my total electricity usage was 5,394 kWh—a 22% increase from 2022. Hot tub usage accounted for 85-90% of this consumption. Controlled tests for a short period in November onwards revealed the following when the lodge was unoccupied and hot tub cover in place:
| Temperature Setting | Average Daily Consumption | Percentage Reduction |
|---|---|---|
| 37°C (Normal) | 14.74 kWh | 0% |
| 28°C | 8.36 kWh | 43% |
| 25°C | 6.63 kWh | 55% |
Lowering the temperature when the lodge is unoccupied offers substantial savings. Heating the tub from 25°C to 37°C took about 7 hours, well within the preparation time before guests arrive. Of course, if there are no bookings in the near future then the hot tub can be turned off completely and drained down.
I ran the tests for 12 months and the overall hot tub energy consumption per day was 9.58 kWh unoccupied and 14.24 kWh occupied – note that the maximum power rating of my hot tub was 3.4kW.
Impact on Chemicals
Lower temperatures raised concerns about chemical effectiveness. After consulting BISHTA (British and Irish Spa and Hot Tub Association) and a chemical manufacturer, I learned that while chemicals dissolve slightly slower at lower temperatures, they remain effective. Activating the jets can help dissolve them more quickly. Additionally, lower temperatures slow down bacterial growth—an added bonus!
Annual Savings
By maintaining the hot tub at 25°C during unoccupied periods, I estimate a yearly savings of approximately 1,450 kWh, translating to about £350 at 2023 energy prices. Combined with the gas savings, this represents a significant reduction in running costs.
Recommendations for Owners
Based on my findings, I recommend the following practices for lodge owners and hot-tub maintenance:
- Set the lodge thermostat to 10°C during extended non-occupancy to prevent frost and damp.
- Lower the hot tub temperature to 25°C when the lodge is unoccupied for short periods but needs to be ready for those last-minute bookings.
- Ensure guests are reminded to replace the hot tub cover when not in use. Leaving the cover off for protracted periods will hugely increase consumption especially during the winter months.
- Chemical checks should not be needed during extended or standard non-occupancy, however, should be checked, and the tub temperature increased back to normal the day of the guest arrival.
These measures not only reduce costs but also contribute to environmental sustainability. I have shared these findings with Finlake and encourage other owners to adopt similar practices.These measures not only reduce costs but also contribute to environmental sustainability. I have shared these findings with Finlake and encourage other owners to adopt similar practices.
Conclusion
Running a hot tub doesn’t have to break the bank. With careful monitoring and temperature adjustments, significant savings are possible without compromising guest convenience and comfort. My journey to uncover the true cost of running a hot tub has provided valuable insights that I hope will benefit other lodge owners.
If you have any questions or would like further details, feel free to reach out. Together, we can make our lodges more cost-effective and eco-friendly.