Should A Hot Tub Be Left On At All Times?

  • By: Adam
  • Date: April 18, 2022

With the best will in the world, most of us don’t have the time to use our hot tubs every day.

Believe me, I wish I could be in there every night after work! I’m sure you feel the same way!

On those days where we stare longingly out of the window at our tubs, sometimes we start to think about turning off the hot tub.

After all, if it’s not in use then it’s just sucking up electricity and mocking us, right?

Actually, no. Turning off your hot tub when it’s not in use is a bigger waste of time and power than leaving it running.

Let’s take a quick dip, into why that is.

Running Costs

Did you do your research before you bought your tub? If you did you may have found out that when in use, a hot tub uses between 3-7.5 kilowatts of energy an hour. (kWh)

The average cost of electricity here in the USA is 12 cents per kWh so let’s say you’re in a medium sized tub for 2 hours. It’ll cost you $1.20 for those two hours.

Now let’s say you use the tub 3 times a week.

The cost of using your tub is now $3.60 a week. Not bad right?

Here you might be tempted to think that turning it off when not being used is going to keep your overall running costs nice and low.

The problem is that the average kWh usage is worked out for a running tub, not a tub that needs to heat 400 gallons of water every time it’s used.

By turning off your tub when it’s not in use you are allowing the water to cool.

When you switch it back on, your heater now has the mammoth task of heating up hundreds of gallons of water from scratch.

Here’s the math to really drive home how much more it’ll cost you to turn the hot tub on and off.

Cost of turning the tub on and off

Let’s assume that you have a 400 gallon hot tub.

The water in the tub will match the air temperature when the tub is shut off.

I’ve chosen the average spring temperature across all states which is 55°F. To use the tub the heater needs to raise the temperature to about 102°F.

Using this calculator, you can see that heating a tub from scratch will use 45.97kWh. If we then multiply that by the cost of electricity, we get a cost of $5.51.

To work out how much it will cost us to do this three times a week so that we can use the tub for two hours at a time we need to do the following calculations: (3 x $5.51) + (3 x $3.60).

The total running cost for a tub that is used for two hours, three times a week and shut off in between uses? $27.33. Over the month that is $109.32.

Cost of leaving your tub running

Now let’s have a look at how much it costs to leave your tub running.

Most hot tubs have a sleep mode which you activate when you’re not using the tub.

In sleep mode, the tub will keep the water at around about 82°F until you want to use the tub. If the temperature dips below this number, the heater will activate.

The cost of maintaining a steady temperature is negligible, around 1kWh.

This is because the heater activates as soon as the temperature drops below 82°F. In general, the heather only needs to raise the temperature by a degree or two.

This barely factors into the cost as the heater only needs to activate for a few minutes. So even if the heater needs 10 minutes to raise the temperature to 82°F it’ll only cost you 2 cents.

When you want to use the tub, the water only needs to be heated from 82°F instead of whatever the ambient temperature is.

So, using the calculator again, we can see that heating 400 gallons of water from 82°F to 102°F will use 19.56 kWh.

If we use the tub 3 times a week, that 19.56kWh to raise the temperature is going to cost us $7.04 a week. Plus the running cost for the two hours we use the tub (3 x $1.20) which is $3.60. For the three times we use the tub, it’s going to cost us $10.64.

Now, in this scenario we do need to add in the cost of the sleep mode. So let’s assume that the tub needs to use that 2 cents of energy 10 times a day to keep the water at 82°F, that’s 20 cents a day. To do that all week it’s $1.40.

Our weekly cost of leaving the tub in sleep mode until we want to use it, is now $12.04. Every month, that is going to cost us $48.16. That is less than half the cost of turning the tub on and off!

You do need to remember that these prices are rough estimates based on averages. Depending on where you live and how often you use your tub, the cost may go up or down.

Even so, it’s clear to see that turning your tub on and off just isn’t economical.

When Should You Turn Your Hot Tub Off?

There are occasions when turning your hot tub off is the best course of action.

If you know you won’t be using the tub for a few weeks or even months, definitely turn it off.

This is often the case when your hot tub is in a vacation home that you only use in the summer.

Also, you should turn your tub off whenever you do a deep clean or any maintenance.

You don’t want any nasty shocks from wires when you’re cleaning or repairing your tub.

Final Thoughts

It might feel counterintuitive to leave your hot tub running, but the reality is that you will save a lot more money and waste less energy.

You’ve seen the math, and numbers don’t lie!