Practical Tips for Energy Savingsfor hot tubs

What to think about when heating a hot tub depending on use!

- Use a Good Cover: Ensure your hot tub has a high-quality, insulated cover to minimise heat loss.

-Reduced Temperature: Lower the temperature slightly when not in use. Even a few degrees can make a significant difference in energy consumption.

- Insulate: Add extra insulation around the hot tub if possible.

- Timer: If reheating, use a timer or smart controller to start heating a few hours before you plan to use the hot tub.

What’s the best way to heat your hot tub! lets look at the time and energy required to heat a hot tub.

Looking at 3 different energy supplying methods solar thermal, Immersion heater and Heat pump.

What’s the most efficient way to use your hot tub (maintain the heat or reheat)

 Calculations for both situations

Hot tub of 1500ltrs, that heats to 39degC and can lose 2DegC in 24 hours for a 7-day period. We can assume a 6kw energy supply, to heat the hot tub with either an immersion, solar thermal collectors or a heat pump

situation 1 , the hot tub will drop from 39DegC to 25degC.

To heat this volume by 14DegC it will take around 24kwh to reheat. (Assuming 5DegC ambient air temperature).

 Reheat:

 To reheat the hot tub back to 39DegC (@ 5DegC ambient) it will take:

 Immersion heater = 4.1hrs @100% (7hrs is more accurate with heat lose, ambient temp and flow rate)

Solar thermal = 9hrs @ 45% efficiency (using a 10 watt pump)

Heat pump = 4.1hrs (@ COP around 3 real heat time of around 5 to 7hrs)

Situation 2, Assuming a temperature drop of the hot tub in 24hrs is 2DegC. To heat this volume by 2DegC it will take 3.48kwh to reheat. (Assuming 5DegC ambient air temperature).

Maintaining the temperature:

 To Maintain the heat tub at 39degC (@ 5DegC ambient) it will take:

 Immersion heater = 35 minutes @ 100% efficiency

Solar thermal = 1hr 17 minutes @ 45% efficiency (using a 10 watt pump)

Heat pump = 35 minutes (@ COP 3 real heat time of around 1 to 1.5 hours due to ambient air temp)

Ultimately, the best approach depends on your specific circumstances and preferences. The climate of your region and ambient air temperatures. For some, maintaining the temperature might be more convenient and energy-efficient, while for others, reheating only when needed could offer better savings. Some of the best results may be using hybrid energy systems such as immersion heater with solar thermal to heat the hot tub.

Conclusion

 Immersion heaters, can be operated efficiently with a well-insulated hot tub.

Solar thermal collectors are the cheap and most energy efficient system to heat a hot tub. With a well-insulated hot tub and a system designed to the climate. Smaller systems designed to over come the heat lose of the hot tub, over a full day. Can be an even cheaper option depending on usage.

 Heat pump systems are the most expensive installation costs but when the heat pump is oversized or sized to overcome low ambient temperatures they can heat a hot tub very quickly. Reducing their energy cost and speeding up the process of heating the hot tub.

Both Heat pumps and Solar thermal will operate more efficiently in higher ambient temperatures allow for faster heating times.