Another solar pool cover for odd shaped pool thread

[Cwiggs]

Hello TFP,

I'm getting ready to buy a solar cover for my pool to help retain the heat at night and extend the swimming season.

My pool is an odd shaped "elbow" pool that I usually treat as 2 pools when I measure it. One side is about 18' by 13', and the other is about 18' by 15.7'. I've attached a very crude sketch of the pool.

My plan was to buy something like this and basically cut it in half to have 2 20'x40' pieces. Then I'd cut the 20x40 pieces to fit each side of the pool. The only issue I see is I think the 18' sides are actually a little longer than 20' if I measured them right up to where they meet on the upper-right side of the pool. I figure there might be about a small triangle sliver of the pool that wouldn't be covered, with the triangle being 2-4'?

How does that sound?

 

[kevinskii]

It sounds like you have a good plan. With my first cover I dreaded any heat loss, so I trimmed it to be snug against every wall even though everyone told me that a small gap would make no difference. With my current cover I have a 2" gap on either side, which adds up to a lot more square footage than your 2'x4' triangle. And guess what? They were right. It makes no discernible difference.

 

[Pool_Medic]

IMO solar blankets are a break even in terms of energy savings vs what you pay for them plus the nuisance of off and on time. I have had pools so I can look at the water, not some ugly dirty piece of plastic.

 

[Cwiggs]

IMO solar blankets are a break even in terms of energy savings vs what you pay for them plus the nuisance of off and on time. I have had pools so I can look at the water, not some ugly dirty piece of plastic.

I've never used one and have seen a lot of people saying they aren't worth it. The data between a cover vs no cover is pretty substantial though. In Phoenix with a heat pump the different is about $635 to $965 in savings per season!

I plan to use on of these DIY rollers to make it easier to take on/off. We will see how it goes, maybe I'll ditch the cover but at the end of the day I'm not spending $600-$1100 per season to use my heat pump. I will however spend $45-$125 per season to heat it.

 

[Pool_Medic]

There is no way you’re Saving that much. They are a PITA and look like a dogs breakfast 90% of the time. You can’t heat your pool for that cheap, I know.

Cover free can help save some heat loss but so can only running your properly heat pump when ambient air temp is above 65 degrees. Yes that means running it during day time only, off at night.

I do spreadsheets for clients that reflect when they swim versus ambient temps. No swimming in cold weather means we dial down their vs pumps to insure the heat pump stays off.

 

[Homebrewale]

IMO solar blankets are a break even in terms of energy savings vs what you pay for them plus the nuisance of off and on time. I have had pools so I can look at the water, not some ugly dirty piece of plastic.

While I don't have any data, a solar blanket costs me about $30 per year. I do know it prevents my pool from dropping several degrees overnight and if I leave it on during the day, the temperature rises more than if it is off. Considering the cost to heat a pool, I have a good feeling it is more than break even.

 

[kevinskii]

My rough calculations agree with what Pool_Medic is saying in terms of cost. With roof top solar it's about a wash. The cover is indeed an eyesore when it's on, and if I didn't have a rectangular pool with a reel I can imagine it would be a hassle to move.

However, the cover does undoubtedly prevent a few degrees of evaporative heat loss at night. Even 2 or 3 degrees savings can mean the difference between having a pool that will reach the mid-80s in temperature by late afternoon, versus having a pool that is at 86+ degrees during most of daylight hours. For me that makes the cover worth it, but my pool gets a lot of use. Your mileage may vary.

 

[scdaren]

There is no way you’re Saving that much. They are a PITA and look like a dogs breakfast 90% of the time. You can’t heat your pool for that cheap, I know.

Cover free can help save some heat loss but so can only running your properly heat pump when ambient air temp is above 65 degrees. Yes that means running it during day time only, off at night.

I do spreadsheets for clients that reflect when they swim versus ambient temps. No swimming in cold weather means we dial down their vs pumps to insure the heat pump stays off.

We use a heat pump to heat the pool in the early and late season. With the cover on, we lose about 3 degrees overnight, with it off, about 6 degrees. My heat pump heats the pool about 1 degree an hour, so it's about 3 hours of run time per day the cover saves. It consumes about 7.5kw of power, so it's roughly 22.5 kwh per day. I'd say we run the pump for maybe 2 months out of the year, so let's say 60 days, that's 1,350 kwh. I usually try and run it in the "part-peak" part of the day when my power cost about $0.30 per kwh. So do the math, it saves me about $400 per year. Covers cost a bit over $100, and last 2 years (usually, last year with all the soot from wildfires it was toast after 1 year), so let's say it saves me $350 a year. Maybe a little more in chlorine, my pool uses less of it when the cover is on.

That all said, I hate the cover. It's a pain to take off and put back on, it's ugly, it gets all dirty and gross and dumps dirt in the pool when you take it off, and honestly probably dissuades the wife and kids from swimming when I'm at work.

So yeah, I think I agree with you. This year I've been planning to skip getting a new cover and see how it all ends up. Maybe experiment with running my heat pump at night when it's cooler but when power costs half as much.

Edit to add -- your local cost of energy, whether electric or gas, makes a world of difference here.

 

[Newdude]

When I used my heater it cut the $600-$800 monthly cost on half. It was beyond worth every penny and hassle.

When I stopped using the heater it worked awesome when the air temps dropped for 2 or 3 days. The pool stayed warm like it didn’t happen. More than 3 days and it no longer mattered. If the air was a high of 60 and the cover kept the pool at 67, it was a moot point that I saved some night time heat loss. There were many times though that the weather was iffy and the cover kept the pool just warm enough to take the edge off.

Of course it was unpredictable and all over the place. The times it helped rarely lined up with our plans thanks to Murphy’s law.

 

[Revlus]

I've never used one and have seen a lot of people saying they aren't worth it. The data between a cover vs no cover is pretty substantial though. In Phoenix with a heat pump the different is about $635 to $965 in savings per season!

I plan to use on of these DIY rollers to make it easier to take on/off. We will see how it goes, maybe I'll ditch the cover but at the end of the day I'm not spending $600-$1100 per season to use my heat pump. I will however spend $45-$125 per season to heat it.

I tried these for cover sizes (2 sections for my also weird shaped L pool), and these things really didn't last... I got one season out of them. Let me know if you want to discuss the problems I had directly.

 

[Revlus]

Also, for what it's worth.... I have an undersized heat pump for my size pool from the previous owners, and the pool cover completely saves me DAYS of time reheating the pool to where the wife and kids really love the water, and as mentioned above, it's because of those random really cool days where it retains the heat... but also in general it stays a good 4 to maybe 6 or 7 degrees warmer than otherwise. Unfortunately for me, I can't heat 35k gallons very fast... so it's pool cover for the win.

 

[scdaren]

Also, for what it's worth.... I have an undersized heat pump for my size pool from the previous owners, and the pool cover completely saves me DAYS of time reheating the pool to where the wife and kids really love the water, and as mentioned above, it's because of those random really cool days where it retains the heat... but also in general it stays a good 4 to maybe 6 or 7 degrees warmer than otherwise. Unfortunately for me, I can't heat 35k gallons very fast... so it's pool cover for the win.

It's generally considered best practice with a heat pump to set it at the temp you want, and let the pump more or less maintain that temp. Is there a reason you are not doing that?

Trying to reheat the pool, as you say, takes forever and is a lot less efficient. Especially in a 35k gallon pool. My pool is 15k gallons and I have pretty big heat pump, probably oversized at 140k btu, and still takes a few days to heat up from cold. I tried just heating it up for the weekends my first season, it was pretty frustrating, until eventually I realized I was doing it wrong.