The heat loss to cost ratio really depends whether you're talking about public tubs in a commercial setting, or private ones sold to homeowners. We tried to remember to turn ours down 10 or 12 degrees when we left it, but it didn't have the timer dial that counts down after you turn on the heat. This was a while ago though, so I can absolutely believe that modern tubs might only heat up when you tell them to. Ours stayed close to temperature all the time though. (Installed 12 or 15 years ago, but still installed.)

Most tubs that I've seen aren't kept at temp.

During use is the largest concern. And even that amount of energy is very small compared to what can come off the surface whenever it's opened.

The heat lost through the sides and bottom will actually be negligible compared to the heat lost through the surface of the water.

Which is usually mitigated by a thick styrofoam lid placed on top of the tub when not in use.

If it's heating over the setpoint temp, it shouldn't have anything to do with the new pump. No matter how fast or slow the new pump is going, (as long as it's going fast enough to close the flow sensor interlock), the heater should be controlled by the temp sensor.

I used to have one. The lid folds in the middle, is heavy and the foam is usually soaked from condensation. Most of the time I'd just flip one side open, but if there were more people we'd take the whole thing off.

The tubs I've seen let out enough heat to melt snow in a foot or so radius around the opening, if that help.


...not the best place to look. I tend to never trust home shows. Be very wary. I know a few hot tub dealers personally and we pick up jobs from them often and one in particular does a lot of those shows.

Most of the dealers there are pretty slimey, hate to say it. They'll make their hot tub seem like the greatest deal and like you're getting it for a steal. They bring in sales people from their line to smooth talk you. I know some dealers sell their hot tubs at a greater cost at the shows because they know they can.

Not saying I blame them, it's just how it is.

That said, I'd never want a maax hot tub personally. It's just not a brand name I'd associate with quality.

Any hot tub will look fancy and high quality on the show floor, even a POS costco tub. What I deal with are those tubs 5-10 years down the line. The difference between a quality hot tub from an overpriced crappier tub is this: you'll see the repair man less often (the common repairs ranging from $400-1200), and spending less in electrical costs from proper insulation.

Like I said, I recommend 5 brands.

Hot springs (and it's twin under a different name Calderra), Jacuzzi (and it's twin under a different name Sundance), Marquis, D1 (recently bought up by jacuzzi), and Nordic (if you want a mid price tub without sacrificing quality).

Hot springs/Calderra being my personal favorite for a few reasons.

Hope this helps.


A tub is full of nooks and crannies, plumbing, insulation of various thicknesses. Ours would be impossible to calculate based on anything but actual consumption. Most tubs that I've seen aren't kept at temp.

During use is the largest concern. And even that amount of energy is very small compared to what can come off the surface whenever it's opened.

Fortunately you have a nice little metered heater that gives a specific output.
Mine has a pair of 4.4KW heaters (I run one or two based on ambient temperature, what's it's plugged into and if I'm paying the power bill or not). And then there is evaporation and steam losses.

So, what you want is a data logger that logs on time vs off time of your heater.

Figure out how much on time is required for top on or top off operation and use the energy input calculation.

Conduction through the Styrofoam - Assume the foam is 42° on one side and 7° on the other. This will give higher than actual loss, but the error is probably two orders of magnitude less than the next part.

Natural convection evaporation off the water surface. You'll lose heat from the water evaporating and you'll lose some through natural convection to the air.

For simplicity, assume that the tub is well mixed. Without doing any work myself I'm guessing the most significant heat loss will be from evaporation so focus on getting that right.

You should be able to find the relevant equations on Wikipedia and constants/properties from engineering toolbox (or wolfram alpha)

You'll want to measure the actual heater voltage under load and the amperage to get an exact draw number. Ratings are variable at best and real world voltage at the heater varies.

Don't forget to turn off any auto water adding system or it will mess up your results. Also make sure you aren't measuring pump draw, and the circulation pump is on low speed/air jets feed is off.


Hot tubs can be a pain to move without the proper equipment. But it can be done.

I would recommend putting it on craigslist for a couple hundred buck and see what happens. Make sure u post that the buyer is responsible for moving the tub.

Some recyclers give a better rate if you recycle just wood, so we saved a bit of money by recycling all our wood in one trip and then making additional trips with the fiberglass and spray foam stuff.

We thought about advertising in the freebies, but I really wouldn't considered this approach, the thought of what it could entail with regards to my insurance made us hesitate. All I need is for some idiot to tear up my house, fence, yard, etc, or even worse hurt themselves while taking the tub out. I'd be bent over a barrel with noooo problems.

We sold one that came with a house once. All we really needed to do was turn off the power, then I disconnected the lines running from the junction box.

The buyer ended up hiring movers who loaded the thing up on a dolly and just wheeled it out. I don't have a lot of experience, but I don't think hot tubs typically have water lines running to them so you shouldn't have to worry about that.

Your 40 gallon hot water tank doesn't go very far to fill up the several hundred gallons needed for hot tub, so their isn't any point to use your hot water lines. They just use their onboard heaters to heat any water you put in it. Which is costly on the cheap models.

That being said, there might also be a drain line somewhere near the bottom, possibly inside the casing.

You can drain the whole thing from there, including the internal piping, and from a couple I have seen they have hose connectors so you can drain them away from where the thing is sitting.


We had a super old tub, and it sprung a leak. We had to take some of the cabinet off, but we didn't have the stuff to fix it properly so it now just has an ugly sheet of plywood there!

I think we want to try to take that fake brick looking stuff and put it around it, not sure if that's a good idea though.

Ozone system

Don't bother. The system will last only a year or two before the ultraviolet output drops and it no longer sanitizes efficiently enough. Might as well stick with your regular water conditioning as a habit.


Replace it or rebuild right away. It's been 15 years, and by now various wound coils in the rotor and stator have fused and now unpredictably pull more current for less output than originally designed.

The motor will keep getting hotter, pull more current, and you'll start blowing fuses because circuit isn't expecting that much. After awhile, replacing fuses will get tiresome and dangerous and each trip might ruin some sensitive circuitry. If you have multiple pumps and a tight budget, replace the main one (main one is used for daily filtration, so presumably it's worn more.)

Pressure Switch

If you haven't replaced it with your heater, replace it now before it goes out and you start getting low water flow error messages. It's a $20ish part that'll save you some grief, and ensure your heater doesn't malfunction and burn out.

Perimeter Lights

If you don't have them, see about building some neat ones. If you do have them, see about upgrading them.