Maintain a temp or heat when planned use?

[Macboy]

So this new pool of ours is MUCH bigger than the last two and it was a bit shocking to see how long it took to get it up to temperature for the kids last weekend. Even more shocking, seeing how much temp was long overnight to the next day - which then means a long run again to get it back to temp. I know as summer sets in and overnight lows aren't as cool this temperature drop will ease but I'm wondering if anyone here has done the "thinking" and come to a conclusion about whether it's more economical to maintain a baseline temp and "turn it up" when planned use is forthcoming or to just let it all cool back down and then bring it all the way back up when use is planned?

I'm ok with it cooling down as I can use the pool as a cold shock swim after my sauna but it takes a LONG time to bring it all the way up. Like 24 hours plus of non stop runtime on the heater and pump. However a cold pool also means any spontaneous use of the pool is a no go since the temp will be way too cold. I don't have the exact stats on how log it takes to achieve each degree warmer but will look into that starting tomorrow as we bring it up to temp for the weekend. In the meantime, any insights from those that have "been there, done that" would be appreciated.

 

[ajw22]

Heat on demand will be the most efficient however as you observe you have to plan for swimming and get the pool up to temperature.

Maintaining a constant temperature will use more energy as heat is lost to the ambient temperature.

Do you have a pool cover?

 

[Macboy]

Yes to the pool cover though it's still sitting on the reel BESIDE the pool. Last night's plan was to mount the reel but it didn't happen. That'll be tomorrow's goal (before we start heating it up) so I can gauge the reheat temp and overnight loss WITH the cover in play.

 

[ajw22]

Things will look better once you get the cover on.

 

[GilesM]

I have the same issue. I just leave the heat pump and the filter pump all the time. Pool covers are ugly so hoping the weather warms up a bit. Our heater is electric and we are on solar, not cost is ok.

 

[linda1]

We have the same issue. Our 250 BTU gas heater takes 1 hour to increase water 1 degree in our 30 ft round pool. We have such temperature swings in Western Pa. which makes it hard. This summer we have the heater set to 80. At that temp, the kids don't seem to mind. For me I need it warmer so I crank it up in the morning if I know I have time to swim later in the afternoon.
We use to have the Fafco Solar panels and they would warm the water up quickly. Last season all of them sprung leaks and we would plug a leak and a new on would pop up. So, we removed them this year. I have to say we really miss them, but with having free natural gas we couldn't justify the cost of the new panels for this older pool. When the pool fails, that's it. No new one.

 

[PoolBrews]

The primary issue here is that if you heat on-demand you'll have to plan ahead for swimming. In my experience this leads to a drastic reduction in pool use. Especially with kids, they'll want to jump in on the spur of the moment, and you can't do that with on-demand. You have to ask yourself - did you pay all that money to USE the pool, or just because it looks good in the backyard?

I've had pools for 40 years. My first was in Michigan and it was huge - 42K gallons. My heater ran all the time - the pool was kept at 87-89 - and we opened in mid May and didn't close until mid October. That pool got a ton of use. My kids and usually about a dozen friends were in many days of the week. Wouldn't trade that for anything. My reasoning was that I bought a pool to use it and why save a few hundred dollars to make it uninviting.

I also used a solar cover to retain heat at night - that helped a lot.

 

[Macboy]

Perspectives. I agree 100% about the spontaneous use. And you're right...we upgraded the pool because we want our kids' friends to want to come here and enjoy it. Perhaps I can find a stash of black tubing and build a solar collector to help a little bit on the sunny days. I'd likely only do it if I could find the materials. If I had to purchase the materials to build the collector - or had to just outright buy the collector then I'd have to question if I shouldn't just "pay" to keep the heater running. And for sure, the cover will make a big difference. I'm interested to see how much of a difference. I'll report back with my findings.

Our 12' round was always open at some point in April and didn't close until after halloween. AND several of those late fall evenings the pool would be found at 102 degrees ; )

having free natural gas

Is natural gas literally free in Pa?

 

[SJPoe]

Based on napkin math, my cover saves me at least 30% on heating costs due to the reduction in losses. Its hard to get an exact number, but based on what the math says I should be losing (and hence how much the heater should be running) versus how much I see the heater running, its close to that. Thats based on a cold night in April, and takes no account of wind which would have made the savings greater (the math assumes still air, perfect heat transfer etc etc).

I'm sure someone could come up with a chart that shows the break even point of covered/uncovered maintenance heat costs vs re-heat from lower temp - but that math exceeds my level of caffeination this morning

 

[linda1]

Is natural gas literally free in Pa?

We have 70 acres that has a natural gas well on the property.

 

[SJPoe]

We have 70 acres that has a natural gas well on the property.

If the gas were free, my wife would have the pool at 95F...

 

[Ticojpunk]

I have an electric heat pump, which heats even slower. I tend to maintain it and run the heater throughout the day from 9am to 9pm. I keep it set at 87, which means, it turns on when the pool hits 86, then keeps going until it hits 88, then turns off, and doesn't kick back in until it ticks 86 again, and so on. Ever heater/pool/climate is different. But if I did have a gas heater, I'd likely try to maintain the temp as long as I was actively using it every day. While on vacation this summer, I'll definitely turn the heater off and just deal with whatever it is when i get back, and run it 24-7 for a couple days to get it back where we want it.

 

[SJPoe]

I'm sure someone could come up with a chart that shows the break even point of covered/uncovered maintenance heat costs vs re-heat from lower temp - but that math exceeds my level of caffeination this morning

I thought about this, and unless my caffeine deprived brain is missing something, whatever you lose by not heating, you'll have to put in by reheating, until the pool hits ambient temperature - at which point you start to make gains. The only question really is where you 'save money' - and best I can tell, its when you would no longer have to heat to maintain a temp, so ambient average temp outside.

With a pool my size, heating 25,000 of water is essentially 1F per Hour tops - and 'ambient' is about 67 these days, and given normal heat loss rates, it would take at least a couple weeks at least to get down to that., and then 20 hours to reheat it - just not a practical thing even if we only swam at the weekend.

A cover reduces the daily loss, hence how much you spend to maintain, but doesn't reduce the cost to actually heat itself. It may reduce the overall cost by 'improving' the efficiency of solar heating by reducing the loss of heat via evaporation, especially on windy days.

Here is a graph from last year when I shut the heater off - the pool was covered, and the overnight temps were dropping into the 30s - the pool took over a week to shed 20F. (88F at the left, 65 at the right)

 

[Macboy]

If the gas were free, my wife would have the pool at 95F...

Ha! Yup. And I wouldn't argue! That would be so nice!

I managed to get the reel cover mounted last night - tricky with AGPs but man alive is it ever handy! It's a little wet at the reel end once rolled up but I'll figure out a way to manage that. I couldn't imagine folding/rolling up a cover this big like we did with the smaller pool.

Does water ever actually reach ambient temperature? I think evaporative cooling always makes it a little cooler than ambient. Okay, maybe that's too hard to definitively say. Afterall what is "ambient" really? We will go from 68 today down to 41 tonight and then only back to 46 tomorrow. I cold plunge in 50-54 degree water......sure wouldn't want to swim in a 42 degree pool!