There are many factors that affect the overall running cost of a hot tub, but the key factors that effect their efficiency would be how they are made and how they are run. Insulation is key to keeping heat locked into a body of water, and different manufacturers insulate in different ways. Entry level models are likely to have less insulation as it is sacrificed to allow for more or the enhancement features such as built in stereos, lighting and waterfalls, and usually extra jetting, whilst trying to maintain a certain price point. Higher end models will be better insulated and also provide all of those features and more in abundance. There are also different qualities of covers that come with hot tubs, again varying in thickness and durability and the materials used. Premium hot tubs will tend to have a higher quality cover as standard where as entry level hot tubs usually come with a cheaper vinyl cover around 2 to 3 inches thick as opposed to the heavier duty 4 to 6” covers with premium brands.
The way a hot tub is installed in terms of location can also have an impact on its overall energy efficiency. Hot tubs positioned close to the house, indoors or in a garden building, or in a generally sheltered area will tend to cost less to run than one which is installed in an open unsheltered area which is exposed to additional wind chill factors. Hots tubs recessed into the ground or semi-recessed into decking can also benefit from the additional layers around them.
Overall running costs are also affected by the amount of equipment they have in terms of numbers of pumps and air blowers, and also how often these features are used and the amount the actual hot tub is used overall. The temperature the water is kept at also makes a big difference. It is estimated that each degree less a spas water temperature is set to, can reduce the heating cost by as much as 10%.
Nowadays, spas also fitted with an air source heat pump to heat the water as opposed to the original inline heater that is fitted at the factory will be considerably cheaper to run overall. Depending on the ambient temperature, a hot tub fitted with an air source heat pump can save up to 80% in heating cost, as well as heating up in a fraction of the time. An air source heat pump will use typically around 1/3rd of the energy of the standard 3kW in line heater, yet produce up to 3 to 4 times the amount of heat back into the water. Air source heat pups are also effective at temperatures reaching down as low as minus 15 degrees centigrade and also reduce heat up times by as much as 60%.
What can increase or decrease the energy consumption?
- The amount of time a spa is in use with the cover off and how frequent the usage is. The more often and longer the duration the spa is in use the more it will cost to run due to heat loss and equipment drawing electrical power.
- The temperature of the water - the higher the temperature the spa has to maintain, the longer the heater will be working to reach and maintain it.
- The better the insulation in the spa the better it will retain heat and not require the activation of the heater to boost temperature.
- Shorter filtration cycles can reduce the power consumption as these cycles activate the pumps to drag through the filter system.
- Using an air source heat pump will increase the energy efficiency of the hot tub, using less power to create more heat all year round.
- Floating blankets can reduce heat and moisture loss and increase the efficiency of the spa. (See our blog on how to reduce running costs of your spa.
- Reducing the set temperature of the water will save heat and mean that the spa is not working as hard to maintain the temperature.
Air Source Heat Pump
Do energy efficient hot tubs cost more up front and how much more?
Entry level hot tubs will cost less to buy but will certainly cost more to run overall due to the fact that they are less well insulated. Often entry level spas will have a single layer of reflective blanket to try and deflect heat back through the spa shell into the water. More expensive premium hot tubs will have better levels of insulation and can reduce running costs by more than half. Entry level spas range from £4,000 to £8,000 whilst premium hot tubs can cost from £12,000 to £22,000. Each brand tends to have different ranges and typically features such as insulation improve as you go up through each range. Premium hot tubs will also tend to show better performance in the filtration system and most importantly the massage performance as well as just costing less to run.
How much money can an energy efficient hot tub save you compared to a traditional one?
As technology has advanced over the years, hot tubs generally have become cheaper to run, especially at the higher end of the market. We know from Smart Tub data with brands such as Sundance Spas and Jacuzzi that hot tubs in real life settings in the UK over the last two years have been using on average between 5 to 6 kW of energy per day which at the current energy cost cap of 30p puts them at costing around £1.50 to £1.80 per day. Testing on other spas without this technology can use anywhere between 8 to 15+kW per day depending on how they are insulated so costing between £2.40 and £4.50+. Using an air source heat pump typically reduces costs by around half.
How do solar powered hot tubs compare in terms of energy efficiency?
Using solar energy to generate power is great but won’t be powering the hot tub directly as it is not a consistent power source. It will vary with the amount of light on any given day. It does however massively reduce the amount of power being taken from the grid and will massively reduce the overall electrical power consumption of the property taken from the grid. Older tariffs will also be paying the property owner back so can offset the running costs of any appliance in the household, including the hot tub!
Insulation is important, but how do I know if the hot tub I'm buying has enough?
The answer to this is that the more insulation is packed into the small area inside a hot tubs cabinet the better insulated the spa will be. Testing carried out by the California Energy Commission for all leading manufactures sets the standard and it has been shown that methods such as fuol foam insulation usually have the best performance in running costs and energy consumption. It is important for consumers to ask a dealer to show them inside the spa they are looking at and to explain why they insulate their spas in this way. You will be able to see which has the most insulation usually and also which is creating the best seal between the spa water and the outside elements. A few brands can also prove what their real life running costs are but if they cant, California Energy Commission testing data is readily available on line and a good reputable dealer won’t try to hide it. If the insulation explanation you are getting from the dealer does’t quite make sense you can always fall back on this data and compare between brands.
How do I know if the heaters are efficient when I'm shopping for a tub?
The answer to this is that the heater will be of a certain rating, usually between 1.5kW and 5.5kW. This tells you how much power goes in and what comes out of the heater in one measurement. Titanium coil heaters can be found on some premium brands and these will last longer and be more corrosion resistant. The most energy efficient heaters are now air source heat pumps and hot tub manufactures are allowing them to be retro fitted to most hot tubs on the market and those already out in the world. New spas being manufactured are now also coming Air Source Heat Pump ready, which means the internal plumbing has already been installed if you were to choose to have one as an upgrade over the standard internal in line heater the spa comes with. The savings are well worth the initial outlay, especially with rising energy costs around the world.
Contact MySpa for more info on hot tubs and their efficiency
