My hot tub uses 49% of my electricity per month...lets fix that.

[gotbeans]

I need an arctic cover for this one, it’s fairly new and haven’t sprung for it yet. I have packed much of the free space inside it with more insulation and spray foamed all the joints.

Hadn’t considered sitting it in a bathtub of more insulation ?

More insulation is like more solar panels.. it's an addiction
The foamular holds up good against chlorine fumes etc it is a decent top on a hot tub. If you coat it somehow even better but yea it's pretty strong and easy to work with.
If you plan to use it get https://www.amazon.com/Double-Japanese-Flexible-Cutting-Woodworking/dp/B0BTBDX427/ to cut it. It's better than hot knife, sawzaw, hacksaw, wood knife, circular saw, etc. I've used every saw and these are the best, probably cuz the blade is so thin... cuz hacksaw is second best but have to use the blade only since the top part is too fat

 

[Tripplett]

Like someone else said my Watkins Hot Spring hot tub has a small 120v circulation pump that runs all the time. It’s much more efficient than the tubs that fire up the large 220v pumps hourly for circulation.
Also getting a quality cover can make a huge difference. If your cover is over 5 yrs old and is heavy (soaked with moisture) it’s time to replace it.

 

[Balrog006]

Like someone else said my Watkins Hot Spring hot tub has a small 120v circulation pump that runs all the time. It’s much more efficient than the tubs that fire up the large 220v pumps hourly for circulation.
Also getting a quality cover can make a huge difference. If your cover is over 5 yrs old and is heavy (soaked with moisture) it’s time to replace it.

Mine fires up one of its 240v pumps to circulate and for the cleaning cycles- but only at a low speed. Under low loads and speeds 240v motors are more efficient than 120v ones pushed.

 

[S Davis]

So a few years ago, I bought an old broken down hot tub for $300 and restored it to working order. This took me about 2 months since all the frame wood was rotten and all of the jets were leaking. I re-sealed everything, rebuilt the 2 main motors and added an additional circulation pump for heating. I also bought a brand new control module with a 5.5 kw electric heater.

Fast forward to September 2023 and I have installed a 5kw solar system with a 30kWh battery that is working amazing. Here is the graph of my solar / consumption:

View attachment 182668

My hot tub heats 10-11 times per day using avg 6100w for 20 mins each time. This ends up being about 21.9kWh per day, 657kWh per month. This is nuts...I know people on this forum say that a hot tub really drains the power but I had no idea!

My solution was to purchase a natural gas tankless water heater off of craigslist (cost me $100) and use that in place of the electric heater currently in use:
View attachment 182669
I tested it and it seems to be heating properly up to 140 degrees.

It is not going to like the chemicals, they will eat the heat exchanger. Also those units are designed for a 60-70 degree heat rise through the unit, when feeding it with already heated water it will probably cycle on and off repeatedly as it hits its high limit. Will it work? probably but not well.

 

[Donny Hucklebuck]

Mine fires up one of its 240v pumps to circulate and for the cleaning cycles- but only at a low speed. Under low loads and speeds 240v motors are more efficient than 120v ones pushed.

My tub has the small circulation pump but it is 230v, so it must be more efficient than a small 120v pump or doing what your doing,
i did some research on tubs, watched some YouTube vids, one gentleman claimed running the bigger pump works better for keeping the water clean than having a small one running 24/7 which makes sense. On an other note get ready for big gov pushing, making people install new more expensive variable speed pool pumps. It’s kind of the same argument running a high amp motor 6 hours of the day or the big variable speed that can run at low rpm 24/7 apparently using less energy. Some guys say it doesn’t keep the water filtered enough, so you have to eventually run them at higher speeds anyway

 

[time2roll]

My VSP runs about 6 hours at 80%, 12 hr at 30% then stops for the day. Seems to work well.

 

[tmprof]

It is not going to like the chemicals, they will eat the heat exchanger. Also those units are designed for a 60-70 degree heat rise through the unit, when feeding it with already heated water it will probably cycle on and off repeatedly as it hits its high limit. Will it work? probably but not well.

I installed an O3 creator in my tub a year ago and it reduced the amt of chemicals I use in my tub dramatically.

Sooo! I started my install last week. Some parts went well, others, not so much... As to the actual tankless..that worked out well and installed properly:



I haven't installed the front yet, but not a huge deal. Re-directing the circulation pump ended up not diverting enough flow to the tankless so it never started heating. My original plumbing was overly complicated with 3 different one way valves to make sure the water went the proper directions. I ended up cutting it all out and starting over.


This time, I'm separating the main inlet / pumps plumbing from the circulation / heating plumbing. To do this, I'll need to drill 2 additional holes in the tub. I have an old tub with an unusually large filter area with plenty of room for an additional inlet for the circulation pump. The 2nd hole will be where the hot water will be added back into the tub. Thankfully, there's an area near the circulation pump where you can drill out and add an additional vent / outlet. Currently, I'm waiting on a few plumbing parts to come in the mail that I couldn't get from Home Depot.

Stay Tuned!
-Troy

 

[tmprof]

Ok, I completed my hot tub project this week! I ended up buying a wifi controlled smart switch that has a temp sensor:

Inkbird 308 wifi

It connects to the tankless water heater and turns off when it senses the temperature at 98 degrees.
I put the circulation on a basic smart plug that connects to my home wifi that turns on the pump every 3 hours for 30 mins at a time (pump only pulls 340 watts). When the tankless senses water flow and turns on if the temp is lower than 98 degrees. I have the tankless set to heat the water to 140 degrees so it doesn't take long to get the tub water to 98. Then it turns off the tankless. The heating process seems to take about 20 mins and the circulation pump runs with the heater off for another 10 mins.

Here is the final plumbing:

 

[Osmethne]

Nice. Have you run the numbers to see what you're saving?

 

[tmprof]

Nice. Have you run the numbers to see what you're saving?

I need to wait a month to see how my avg kwh changes, but here's some rough #'s

Old system used about 660 kwh per month
Estimated new system should be about 32.4kwh per month and most of that will be the circulation pump, not the actual heating part

 

[teal95]

I'll be revisiting this in a few months when I'm finally making more power than I'm using, basically looking at the hot tub as a dump load. I'm envisioning putting a heating element inline with the circulation pump with some basic temp controls, only shutting it off if it's above ~100F.