Do hot tubs use a lot of electricity? How much energy do they consume per use and per month?
Are they expensive to run? And is there a difference in running them in summer or in winter?
How much does it cost to run small and big hot tubs? And how to run them economically in order to get their benefits without breaking the bank?
I’m an electrical engineer, and these are the questions that I will be answering in this short article in order to help you before you buy a big, fancy hot tub and spend a lot on money everytime you turn it on.
Without further ado, let’s begin!
Do Hot Tubs Use a Lot of Electricity?
Yes, hot tubs are among the biggest appliances that consume a lot of electricity when they are running, and the total energy usage might differ from one hot tub to another, and from one user to another for the same hot tub model and brand.
Some of the factors that affect the electricity usage of a hot tub are:
- The size of the hot tub and how much water it contains.
- The heating element and the pumps ratings in Watts.
- The frequency of use.
- The temperature you set it at.
- The surrounding temperature and the location of the hot tub.
- The efficiency of the hot tub’s insulation.
- Whether you keep it on when it is not in use or not, and the use of a cover to maintain the temperature when not in use.
- The operating mode.
- And some other factors.
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How Much Electricity Does a Hot Tub Use?
A hot tub uses anywhere between 1,500-7,500 watts of electricity in order to run, depending on its size, manufacturers design, and on the operating mode.
A small hot tub for 2-4 users might use between 1.5-5.5 kW, and a bigger hot tub for 5-8 users might use between 3.5-7.5 kW of power while running.
How Much Energy Does a Hot Tub Use per Hour?
These translate into 1.5-5.5 kWh (kiloWatt-hour) of energy used per hour for the small hot tubs, and 3.5-7.5 kWh of energy used per hour for big hot tubs, which is the value that the utility meter records, and what you get billed for.
How Much Electricity a Hot Tub Uses to Run per Day?
Assuming the average-sized hot tub that uses around 5.5 kW to run, and assuming that it takes around 10 hours to raise the water temperature from 20 to 40 C, then it consumes around 55 kWh of energy in order to achieve the desired temperature. (5.5 kWh X 10 hours = 55 kWh)
To retain the temperature in a range that is close to that level, the heating element will turn on and off regularly and would typically consume less energy per hour than what it consumes when it is heating the water from the starting point.
How Much Electricity a Hot Tub Uses per Month?
On average, assuming that you run the hot tub twice a week, then it would use around 440 kWh of electricity per month, assuming the average consumption of 55 kWh per one use. (8*55 = 440)
The total energy used by the hot tub per month depends on the number of times you turn it on, and on the conditions every time you run it as the starting temperature might differ from day to day.
These wide ranges happen because of the wide variety of hot tub models from different brands that follow certain standards and create hot tubs with different preferences and operating modes.
For example, Caldera Spas create the same size and model of a hot tub with two different ratings of heating elements, 1-kW for countries that use the 110-120 volt rating (e.g. US & Canada), and 4-kW for the countries that use the 220-230 volt rating.
And both hot tubs would use the same rating of the jet pumps.
The reason here could be to limit the electric current used to supply the heating element when used in a 110-V system, and thus, reduce the sizing of the cables and protective devices that need to be used.
And while the 1-kW hot tub might use less electricity at any moment for operating the heating element, but it would then require more hours of running in order for the water to achieve the desired temperature.
Another reason for the big differences in electricity usage of hot tubs is the fact that some come with one jet pump, and some with two pumps.
And some models, or operating modes of a certain model, allow for the heater to run simultaneously when both pumps are running, while others don’t run the heating element when both pumps are running.
The previous numbers can indicate the electricity usage per hour in kWh terms for the hot tub.
For example, a hot tub that uses 3.5 kW of power when running, would consume around 3.5 kWh every hour of its operation, and so on.
And the total amount of energy used by the hot tub per day or month depends on the factors listed in the previous section, such as the set temperature, the surrounding temperature, the quality of insulation, the usage patterns.
For example, when turning on the hot tub while the water is at the temperature of the surrounding, it might take anywhere between 12-48 hours until the water reaches the set temperature.
Some manufacturers will give you an estimate of how many degrees the water temperature will rise every hour after you turn it on.
And this varies from one manufacturer to another, and from one model to another even from the same manufacturer.
For example, Sundance Spas estimate that the temperature would rise by 2-3 degrees every hour for the bigger models that use 3.8-7.3 kW of energy when running, and around 4-5 degrees every hour by smaller models that use 2.8-5.4 kW of electricity.
This difference comes from the fact that smaller tubs have much less water, which makes it easier for the same heating element to raise the overall temperature of the water at a faster rate.
Assuming that you run one of the smaller hot tubs that uses around 5.4 kW of electricity while running, and it is set to raise the water temperature from 20 C to 40 C, then it might take only five hours in order to achieve the desired temperature.
This means that it would consume 5*5.4 = 27 kWh per run, and based on the average use of twice per week, it would consume around 216 kWh per month. (8*27=216)
And there are other factors that contribute to time needed to achieve the desired temperature for the hot tub water, such as: the difference between current temperature of the water and the surrounding air on one side, and the set temperature on the other side, the heating element rating, the insulation quality and the ability to retain heat.
For example, a Lay-Z-Spa might take 5.5 hours to achieve 40 C for the water if the initial temperature and the surrounding temperature where 30 C, and it might take up to 18.5 hours if the starting point was from 10 C.
How Much Electricity Does a Hot Tub Use in Winter?
During winter, the hot tub might use 1.5-3 times the electricity it uses in Summer as the outdoor temperature and the initial temperature of water are usually much lower, which requires more energy and time for the heating element in the hot tub in order to raise it to the desired temperature.
How much electricity the hot tub would use per month depends on how low the temperature is, the desired temperature you set it at, the insulation of the hot tub, and the use of a cover during the water heating time.
Are Hot Tubs Expensive to Run?
Hot tubs can be a bit expensive to run if you use them on frequent basis, if you set the temperature at the highest level, and if the electricity rates at your area are high.
The water heating elements in a hot tub use a lot of electricity, which makes them one of the biggest contributors to the electric bill.
Other factors that might make running the hot tub more expensive for you are the outdoor temperature, the insulation of the hot tub, and the use of a good quality cover during the water heating time and during the time when it is not in use in order to retain the heat for as long as possible.
There are costs associated with replacing the water once every few weeks based on the manufacturers recommendations, and the cost of chemicals you would add to the water, in addition to the regular maintenance costs, but the most dominant cost when running a hot tub is the electricity cost.
How Much Does a Hot Tub Cost to Run?
A hot tub would cost around $3.8 per use for the smaller size, and around $7.7 per use for the larger size, on average, based on the above examples of around 5.5-kW hot tubs that differ in size (number of users and amount of water), and assuming the starting temperature of 20 C and the desired temperature of 40 C.
These are based on the average electricity price of 14 cents/kWh.
That’s how much it costs to run a hot tub per day, assuming that every time you turn it on, it starts with water at the temperature of 20 C.
But if you want to run it every day, then it the daily running cost of the hot tub might be lower as it might retain heat if it had a good insulation, if you used a cover when it is not in use, and if the surrounding temperature didn’t drop a lot.
How Much Does a Hot Tub Cost per Month?
Based on the average use of twice per week, the monthly cost of running a hot tub would be around $30.2 for the smaller size, and $61.6 for the bigger size.
The actual cost of using the hot tub would differ from a user to another based on the tub model and size, the actual surrounding temperature that varies by location and season, the temperature they set it at, the usage pattern and frequency, and the actual energy price as electricity providers charge different prices.
For example, in Connecticut and California, the electricity rates are around 50% higher than the average, while in Idaho and Utah, they are around 30% lower.
Note that the vast majority of these running costs of the hot tub represent the electricity cost, and a small portion represents the regular operation costs of a hot tub such as: replacing the water, adding chemicals, changing filers, …etc.
The cost to run a hot tub in the winter would be higher than the above estimates as the surrounding temperature drops way below the average temperature in the summer, which makes the hot tub work longer and harder in order to achieve the desired temperature and maintain it.
6 Tips on The Cheapest Way to Run a Hot Tub
You can minimize the running costs of a hot tub by following these tips:
- When used outdoors, it is preferred to be installed in the warmest place available with the least air movement.
- Keep the cover on the hot tub when it is heating water, and even after you finish from using it, in order to maintain some heat for the next use.
- Use a floor mat under the hot tub to provide additional insulation and prevent the heat from escaping to the cold ground.
- Don’t set the desired temperature of the hot tub to at the highest setting that it can provide, as every degree higher would cost more money on your electric bill, and the addition becomes higher during the colder weather.
- If you don’t expect the hot tub to be used by many people at the same time, consider getting the smaller size as the amount of water affects the energy usage of the hot tub and the total running cost.
- If your energy provider charges based on the TOU (time-of-use) basis, where electricity prices change during the day based on the hour of using it, then consider turning on the hot tub during the off-peak hours in order to heat the water at the cheap rate, and keep it covered until you want to use it in order to maintain the heat during the high-rate hours.
Hot tubs can use a lot of electricity and add a significant amount to your electricity bill, but they can be useful as using them offers some health benefits and could improve the quality of your life.
How much electricity the hot tub uses depends on many factors such as: its size, its insulation, the pattern and frequency of its usage, and the location where you live.
And the total cost of running the hot tub depends on all of the factors mentioned above, in addition to the energy rates in your area.
Follow the tips in the above section in order to buy and economically run a hot tub that fits your needs, without buying a big one just to impress your friends once a year, and then spend a lot of money every time you turn it on.
I hope that my article was insightful and helpful for you!
If you still have other questions on this topic, please, let me know in the comments’ section below, and I will do my best to help you out 🙂
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