Help, need to insulate my hot tub, any recommendations??

[Nicola3771]

Hi, I am new to the forum and need as much advice as possible.  I recently purchased a used hot tub(only 18 months old) however it is costing a fortune in electricity.  I knew it would be expensive as the electricity charges at my static caravan holiday home are quite expensive at £0.165p per kW, however I think the problem lies with the insulation. When my husband took the side panel off he noticed the pipes were insulated with spray foam and the cabinet has a foil backed bubblewrap however there is a lot of open space inside the cabinet - this could be causing heat loss?? Any ideas on how to insulate it to reduce running costs??

We only use it on a Friday/Saturday, when we leave on a Sunday we put it into sleep mode set at 21 degrees, a friend then puts into onto standard mode 40 degrees on the Thursday so it is warmed up and ready to use when we arrive on the Friday.  It two weekends of use - and the other time being placed in sleep mode it had cost £50 in electricity which seems a bit high. So in 4 weeks it is gonna cost £100! It has recently been serviced so we know it's in good working order, we are waiting for our thermal blanked to arrive (to lie over the water and under the cover) , the actual cover is in good nick so don't think the problem lies there.  We just think the under insulation isn't too good. It's a good branded artesian hot tub and is currently £6,000 new to buy in store.

Any ideas to help reduce running costs would be welcomed!!!!
Thanks you guys

[MrLobster]

Hi Nicola,
The empty space inside the cabinet shouldn't be an issue at all.  I've also got an Artesian tub and I'm in the UK, so probably have similar power usage to you.  Very little heat escapes through base into the cabinet, and the foam on the pipes will be enough to stop any major loss there.

Most of your heat loss will be through the top, especially with the cover off.  We keep our tub at 38 degrees, and with an air temperature of 10c (typical evenings for the last few weeks) and the cover off the heater can just about maintain temperature with the water jets on.  With the air bubbles mixed in with the water jets we lose about half a degree every half hour.

With the UK model I'd expect you have a 3kw heater at most, so running flat out it will chew through a fraction under 50p an hour at the prices you quoted per kWh, or 100 hours of the heater on full.  Worth keeping an eye on your meter, it could be that the caravan park are charging more than you think.

Did the tub get a lot of use over the weekend?  Our use averages about half an hour a day and our electricity bill has gone up less than a tenner a week.  We pay 10.39p/kWh, so on our rate you would have paid £31.50 so far.

Dropping your temperature a couple of degrees would help keep the costs down.  Maybe also turn down the temperature when you get out on Saturday night if the tub won't be used Sunday?

If your friend who turns the temperature back up could check the temperature about 24 hours after you turn it down, that would give an idea of how fast the heat is getting out.  From memory ours drops 6c in 24 hours with the cover closed and heaters off.  I'd expect yours to fall a little faster with the higher starting temperature.

I'd be very interested to know how much difference your thermal blanket makes, I've considered one but don't really have anywhere to put it while we use the tub.  If it makes a big difference I'll find somewhere to store it.

[Tman122]

Hang it over your hard cover.

[MrLobster]

Thanks Tman, excellent idea.  Only downside is I now feel a bit of an idiot for never thinking of that myself.  Never mind, I'll get over it.