Thermal solar died... what next? Replace or electric pool heater?

[bbrock]

Hi TFP members,
My thermal solar finally failed. Two panels split. It is an old system that was installed many previous owners back, but it worked well. Total of approx. 288 sq ft of coverage, 5 panels facing South, 1 panel facing West. We have a large 27 panel photo voltaic system that covers our Tesla Model 3. Less than a year ago, the pump on our above-ground spa failed, and I have not replaced it. So, that will be energy savings b/c that was an energy hog. Also, I do use a thermal solar blanket. We may not replace the spa, so as such we have that energy savings which could go towards the electric pool heater. My system is quite basic. I have a variable speed MaxFlo 1.5 hp pump, but I don't have a smart system.

The dilimena now is that I am not sure if I should replace my thermal solar or get an electric pool heater. My 9 year old sons play year-round water polo, so we'd like to help along that journey. If that means more swim time intermittently in the winter using an electric pool heater, than that may be the better option. The combination of the thermal solar and thermal solar blanket seemed to allow us to be the first pool swimming in the Spring, and last pool swimming in the Fall. Generally, the pool water is already up in the high 70s in March, and maintaining swimmable temps through October.

I am not too mechanically involved. I would not be installing either the thermal solar panels or the electric pool heater. For reference, in 2018 I got some quotes for replacing the thermal solar. One estimate was $5,880 for 6 FAFCO Sunsaver Panels, and the other quote for $6,525 for 6 Solar Industries panels (not sure what model).

What complicates the matter is that I have a metal shingle roof. So, we definitely want the most trusted installer on the roof b/c these shingles dent easily.

1) What would be the more efficient long lasting product - thermal solar panels or an electric pool heater?
2) If an electric pool heater is installed, do I have to install a smart system. I am not sure what that name for that Pentair system is.
3) Would I have to upsize my pool pump from the MaxFlo 1.5 hp vsp?
4) What would cost more to install and ongoing operation - thermal solar vs. an electric pool heater?
5) What panels are best - FAFCO Sunsaver panels, or Solar industries?

Thanks for your assistance.

 

[1poolman1]

All heaters can be stand-alone items, not needing a special control system. Hopefully, you are talking about a heat pump as opposed to an electric heater. For a true electric heater (like was in your portable spa) for a pool, you would really need 3-phase power at your property to be anywhere near efficient. Not likely in a residential area. Many years ago, 30+, in this area we had a very wealthy woman bring in 3-phase power to her residential home and install two large electric heaters. Best estimate was a monthly cost of $3-4,000 per month to heat her pool, and that was at SMUD prices (about 1/3 of your PG&E) then. She didn't care, just wanted a heated pool. I knew the man who serviced her pool up until she passed away. Always kept it at about 78-80 degrees year round. Heat pumps for pools weren't very available at the time.

A heat pump costs very similar to what a home A/C system costs to run as they are, basically, the same thing. Much more efficient than an electric heater. Not a lot of California pool companies are familiar with heat pumps, but the list is growing.
A new heat pump, installed, would cost something similar to the costs you listed as solar installation, IF you have the power available at the install site. If not, the cost to get the power to the pad could be considerable. Then there is the on-going cost to run the heater.

After installation, solar heat is relatively free (yes, you have to pay to run the pump). Obviously, no heat in the Winter.
Solar Industries is the parent company of FAFCO.
If the existing pump was able to run your existing solar, keep it. I have installed those pumps on pools with solar successfully.

 

[bbrock]

Awesome input. Thank you. But solar industries being the parent company, does that mean it’s six of one, Half dozen of the other (basically just the same panel different names)?

Yeah I was talking about an electric pump. I didn’t know a true electric heater is so costly. Thank you for that correction.

So it sounds like regardless an electric heat pump will cost more going forward. And I can imagine if I truly did want maintain a pool at 80° certain weekends in the winter with a large difference in air versus temperatures, that could be costly if I equate it to just being similar to an air conditioning.

 

[dfwnoob]

The other problem is heat pumps are slow. Really, any residential solution that isn't gas is slow (but I'm aware natural gas service is becoming scarce in most parts of California). Which means you'll be running it a lot if you want to keep 80 degrees in the winter and you'll need to continue using the solar cover for sure. It really is just a giant air conditioner running in reverse, so the electrical costs associated with running that are absolutely a consideration.

 

[bbrock]

Thx dfwnoob, 1poolman1.

Sounds like the best thing is just replacing the thermal solar and dealing with a few months of not being able to swim. And to just buy the boys some wetsuits for those months.

 

[bertschb]

I have a heat pump pool heater and in my area with electricity at $.13kWh, it's less expensive than natural gas to heat a pool. But, as mentioned previously here, it's slow to heat. Waaaay slower than gas. It takes several days in the winter to heat the water 25 degrees. Once there, maintaining the temperature is no problem. So, if you want to keep the water at a certain temperature for a couple months, it would be fine. If you want to use it to heat the pool for an event like a pool party, it's a poor choice.

If your thermal solar panels provided the heating you wanted, I'd replace them! Much cheaper than electric or gas.

 

[bbrock]

Got it! Thx bertschb

 

[Dirk]

Just to add a few data points for consideration... As pointed out, there are cheaper ways to control a heater than by using a pool automation controller, but should you decide to venture down that path, know that those controllers can manage more than one heater. My Pentair EasyTouch, for example, is controlling both my gas heater and my rooftop solar heating system. It can do so in several way. Either heater, or a combination of both. I can have both heaters engaged, and the controller will pick which will heat the pool best. Maybe that's solar all day, and then as the sun sets the gas (or electric, in you case) heater kicks in. Or solar on sunny winter days, and then electric on a cloudy day, etc.

Granted, I just racked up three times what you were looking to spend onto your charge card, but I'm generous like that. If you can make the long-term math work, having a choice of heat sources could conceivably be the most cost-effective over time. Guaranteed electricity is not going to get cheaper, so there's that to consider, too.

When they were estimating my solar PV and solar thermal, they kept talking about how many more PV panels I'd need. I was confused until I realized they were calculating how many more PV panels I would need to compensate for a heat pump. Have you had any solar company do that math for you? Maybe instead of more thermal panels, what you need is more PV panels to compensate for a heat pump, which might provide more days of heating annually, while using "free" electricity. If they want your business, for the heater or the extra panels, or the thermal panels, put them to work on running "what-ifs" for various setups. They have the software that makes that relatively easy. And they can do projections, too, to see how well the various scenarios will play out as energy costs continue to rise.

 

[bbrock]

Thanks Dirk. That’s all good food for thought

 

[denwood]

It's hard to beat solar thermal (pool heating only) as you're likely getting 85% efficiency or so from your 288 sq/ft.

288 sq/ft of PV would generate about 2880 watts. Conversely, your thermal solar panels likely produce somewhere around 22K watts of heat energy at 85% efficiency. You'd need a heat pump with COP of around 7.63 and 288 sq/ft of added PV to more or less equate to the thermal solar you have now. My guess is that is a quite a bit more expensive than just replacing your existing thermal solar. That said, if you want to be net zero, adding approx 350 square feet of PV solar would likely be a pretty close prediction, again assuming a heat pump that would have similar output to your existing thermal solar.

My solar thermal system tops out at about 104K BTU (approx 30K watts). With a heat pump with COP of 5, you're talking about 6000 watts (25 amps@240V) to match that output.

 

[bbrock]

Wow Denwod, thanks for that analysis. Seeing those numbers help. Between what Dirk and you have said, I’m really thinking about this.

I emailed my photovoltaic solar rep/company owner to help and give me an analysis.

 

[denwood]

Post back here with what they suggest...it's a very relevant discussion these days. Martin Holiday has been chirping on this topic for some time: Solar Thermal Is Really, Really Dead - GreenBuildingAdvisor

The discussion is not pool heating though..which is a different case scenario entirely vs domestic hot water heating.

 

[bbrock]

I reached out to my PV solar company denwood regarding if my panel/system can accommodate another 40 or 50 amp for a heat pump, and the number of panels that I'd need, but he still has not responded. Anyhow, I don't think it can fit another 40 or 50 amp breaker, and not to mention if a heat pump would equal the cost of an a/c and/or the prices I listed above, if you add on that the cost of more PV panels, it would take a long time to hit a breakeven going that route vs. just replacing the thermal pool solar.

Thus, I am not in discussions with some pool solar companies to come out to replace my system. My biggest concern is if they can work on my metal shingle roof system. I have serious concerns about people going p on my roof to replace it b/c you have to stand and walk on these shingles in a way so as to not dent them. I will see if I can post some pics of my system. Here are some questions:

1) I am looking to replace all the panels. However, should I reuse these original wooden brackets/mounts that one of the homeowners had installed?
2) What type of mounts should be used with a thermal solar system to be mounted to metal shingle roofing?
3) Can thermal solar panels be mounted to metal shingle? Would it be like my PV and use some sort of bracket system?

 

[bbrock]

Here are some pics of my current leaking system.

 

[Dirk]

Here's a bump, but I can't answer any of those questions. I'd ask those of at least three installers, to see if there is a consensus. If you keep hearing the same answer from more than one source, then that's a good sign. If each answers differently, then maybe none of them know for sure.

Either way, explore their contract(s) regarding clauses about damage to the roof due to installation. Make sure that is all going to be in writing. Who's responsible? Who pays? Is it pro-rated? Etc. If they won't guarantee against damaging your roof, that kinda indicates they already know they're probably going to damage it!