Hot Tub Heating Alternatives

[Industrial Toys]

I think I already know the answer.

Someone gave me a free hot tub a few years ago. I heat mostly electrically at .15 CDN/KWH, no time restrictions. I disconnected the hot tub element, not wanting to add to my electic bill. The first year, I used loops of black pipe as a solar heater, which worked well except for the unsightly mess and limited heating window, then built a wood fired boiler that was a lot of work to keep going and wasn't very efficient, plus the smoke blew right in the windows of the house!.

I was considering getting a used oil fired hot water tank and running it on Diesel. But in addition to the expense of the tank and the hassle of putting yet another thing to bed in the winter, would this cost more then just using the electric element? Diesel is about $1.30 CDN/litre.

Thanks

 

[Redneck in training]

Try solar panels. If you can do it DIY it will cost about $2.3/W of installed rated power before subsides or rebates (if you have such a thing in Canada.) What would you do next depends on the type of contract with the utility. In example if you have net metering you don't need to anything. If the sale price is lower than buy price then you can heat the tub only when there is power from the PV available. In example you can use a timer and turn the heater on only when there is satistical probability that the PV generates power. Or you can isnstall a solar power diverter that will send such amount of power to the heater so you will not export any.

 

[Industrial Toys]

Interesting Point. Rather then frick around with insulated piping and having to drain the system in the winter, solar panels would be better. No inverter required. Just hook them up to the heating element. Actually, that might be hard to get 240 volts DC! A lot of panels. I just don't like inverters, even though I can get them for free from a friend!

Watt for Watt, on a small system, what is the difference in cost outlay between hot water solar heating and PV Solar? I thought about it, but am not sure I am up to building a hot water solar array.

 

[KTurner]

Do you want to use it in the winter, or are you just trying to keep it from freezing? If you're just trying to keep it from freezing, toss some (non-toxic) antifreeze in there. Drain/refill it when you're ready to use it in the spring/summer.

Keith

 

[Industrial Toys]

I built a substantial steel frame for it with fork pockets. I put it away in the winter. I have a hard enough time on cool nights making it back alive to the house. Although I imagine the experience of using a hot tub in the winter to be quite enjoyable, I don't know how I would ever find the courage to get out!

 

[KennyG]

Have you got an idea how much electricity it actually uses? I ask because I have a fairly new hot tub and it uses very little power. I don't really notice it. The company that installed it estimated it would not be over $10 a month in the dead of winter.

 

[Industrial Toys]

I keep hearing things like that. I know the heater isn't on all the time, although in the dead of winter, who knows. But, just sayin, if it were a 2000 watt heater, on for 30 days at .15 KWH, that would be $216.00! If it was on a quarter of that time, it would still be $50.00! And that is not accounting for use, with the top open. Thinking about it, I can't imagine even running the circulating pump for ten bucks a month!

I just remembered I had the pack next door here. I looked. The heater is 23 amps at 220/240! That's five and a half thousand watts!. Not that it means the thing uses any more energy at the end of the day.

I think the hot tub people are blowing smoke up your . . .

At ten bucks a month, AND in the coldest time of year, I would have to be a complete Idiot to mess around with my solar piping and wood fired boiler or buying and installing PV panels!

It would sure be nice though.

EDIT: I just did some more calculations. A 100 watt Edison bulb (remember those?) left on continuously would cost a little more then ten bucks a month at .15 KWH.

 

[KennyG]

I wish I knew exactly what it uses but I'm always amazed at how little electricity I use. I get close to but never exceed $200 in the winter (pool pump runs it a little higher in the summer).I know that sounds like a lot to some but I have a large house. I have two baths with heated floors. I run an electric space heater in a three seasons room. The usual appliances- an electric dryer, etc.

When the hot tub is not in use the pump only runs a few times a day for a few minutes. We have not used it for a month or so because of the snow. It's just melting now because I lost the battle trying to keep it clear. It does not lose enough heat through the cover to melt snow.

 

[Redneck in training]

Interesting Point. Rather then frick around with insulated piping and having to drain the system in the winter, solar panels would be better. No inverter required. Just hook them up to the heating element. Actually, that might be hard to get 240 volts DC! A lot of panels. I just don't like inverters, even though I can get them for free from a friend!

Watt for Watt, on a small system, what is the difference in cost outlay between hot water solar heating and PV Solar? I thought about it, but am not sure I am up to building a hot water solar array.

Typical 250W panel will produce about 30VDC at about 8.4A under load. If you want to avoid inverter then divide the rated voltage of the element by 30 to get the number of panels. Then multiply number of panels by the panel rated power to get the wattage of the heating element. You can use smaller element but then the voltage from the panels would be higher. I would still recommend using inverter. It could provide power for your house when the heating element is off.
Panels are in in average 80 cents (USA)/W. 2kW inverter is about $500 USD. If you would use the panels only for the hot tub then you need inverter that can operate in "island" mode. You can get one with modified sine wave. Those are cheaper and the element doesn't care what the sine wave is.
I would guess you need 6 panels and 1.5kW inverter plus something to mount the panels on and wiring. All for about 2000-2500 USD.
The beauty of PV is that it is virtually maintenance free.

 

[bandaidmd]

I just keep mine turned on and pay the bill.
If its not worth the dollar a day to keep it on why bother,drain it for the winter.

 

[EddieWalker]

I have a hot tub that's about ten years old and it stays on from fall to spring. I've turned it off a few times for repairs that took over a month or more during the winter months and only noticed a $20 drop in my bill. Seems like it would cost more to create another way to heat it then you would save just leaving it on all the time. I also have a very good, and fairly thick top on it, so that helps a lot with keeping the temperature constant.

Eddie

 

[dmccarty]

Interesting Point. Rather then frick around with insulated piping and having to drain the system in the winter, solar panels would be better. No inverter required. Just hook them up to the heating element. Actually, that might be hard to get 240 volts DC! A lot of panels. I just don't like inverters, even though I can get them for free from a friend!

Watt for Watt, on a small system, what is the difference in cost outlay between hot water solar heating and PV Solar? I thought about it, but am not sure I am up to building a hot water solar array.

There are now solar panels that have a small inverter built on the panel so you do not need a big, centralized inverter. There are a couple of companies that are selling micro inverters, Enphase is the name I can remember, Enphase Energy.

I took a solar power class last year and the instructor was a builder who built houses with PV power and hot water generation. I forgot the exact numbers but he said a new solar hot water generation system was $8-10K. What ever the exact number, it was VERY high. I asked him if it would be cheaper to just add some solar PV panels. Since panels are close to $1 a watt, so $5,000 dollars buys a lot of hot water for 20-30 years. I have not crunched the numbers to see if spending $5,000 to heat a hot tub makes money sense vs just using the grid. We would love to have a hot tub but I figured a wood burning model would work for us since we have lots of firewood.

Later,
Dan

 

[Lloyd_E]

What about a snorkel stove...

Hot Tubs, Stoves & Equipment - Separates - Snorkel.com

 

[mbohuntr]

Our hot tub really doesn't seem to cost all that much... The snow doesn't melt on top either. I think the newer models are so well insulated that they cost less to keep on. Really nice at 12 below, you don't feel it if you don't waste too much time putting the cover back on...

 

[Redneck in training]

There are now solar panels that have a small inverter built on the panel so you do not need a big, centralized inverter. There are a couple of companies that are selling micro inverters, Enphase is the name I can remember, Enphase Energy.

I took a solar power class last year and the instructor was a builder who built houses with PV power and hot water generation. I forgot the exact numbers but he said a new solar hot water generation system was $8-10K. What ever the exact number, it was VERY high. I asked him if it would be cheaper to just add some solar PV panels. Since panels are close to $1 a watt, so $5,000 dollars buys a lot of hot water for 20-30 years. I have not crunched the numbers to see if spending $5,000 to heat a hot tub makes money sense vs just using the grid. We would love to have a hot tub but I figured a wood burning model would work for us since we have lots of firewood.

Later,
Dan

We have Enphase invereters on our system. They are grid commutated so they don't work "islanded". You need an inverter with DC voltage control on the surce side for stand allone load such as heating. Then the voltage and current on the load side will be proportional to energy available.

 

[Oaktree]

I have a hard enough time on cool nights making it back alive to the house. Although I imagine the experience of using a hot tub in the winter to be quite enjoyable, I don't know how I would ever find the courage to get out!

I thought that would be the case as well, but as long as you didn't dally too long I found you didn't really feel the cold when you got out. About 15 years ago I was dating someone who had one, and we'd often sit out in it (outside, on her deck) in single-digit temperatures and have no problem getting out & going back inside. It was very cool sitting in it with icicles in my hair but feeling warm as toast!

 

[crowbar032]

My friends in Sweden tell me something wood fired is the in thing to have there.

http://www.nytimes.com/2010/10/21/garden/21hottub.html?pagewanted=all&_r=0

 

[Tractor Seabee]

I built a substantial steel frame for it with fork pockets. I put it away in the winter. I have a hard enough time on cool nights making it back alive to the house. Although I imagine the experience of using a hot tub in the winter to be quite enjoyable, I don't know how I would ever find the courage to get out!

My daughter lives in BC outside Vancouver, they use there hot tub all winter long. Lounge out there sipping their hot buttered rums. He is a mortgage broker and claims the hot tub really soothes him down after a busy day at the office.

Ron

 

[shovelmike]

We used our hot tub year round, the biggest hassle I had was burning out heater elements, very hard water here. It was necessary to keep the water warm around the clock to prevent freezing, makes anything wood fired not practical unless it was integrated with a household wood furnace.
We finally ended up giving ours away after 7 or 8 years of use, the wood in the frame was starting to deteriorate at that point. The recipient was in recovery from a bad on the job injury, and hoping to help with his pain...which I hope it did.

 

[Industrial Toys]

Not sure why, but I have been thinking of the wood fired heater again. Thinking of getting some rock wool and building a second skin for the small stove. Probably all a waste of time. I might have mentioned the annoying smoke getting into the house, in summer with the windows mostly open. HOURMETER TOTAL of the 5000 watt heater was 263 hours last eason.