The Low Down on Choosing a Solar Pool Heater
So you're deciding on a solar pool heating system and looking at options. This page will help you get the low down on different types of solar pool heaters and all the things you'll want to consider. There's no doubt, solar pool heaters are by far the longest lasting and cheapest way to heat a pool. In that regard we believe they are the best and most environmentally responsible option - bar none. However, they do have a couple of disadvantages, firstly of course they require a roof space, but secondly, their main disadvantage is that they are not an "on-demand" type heating system like a heat pump...
Solar Pool Heaters vs Heat Pumps / Gas Heaters
Now regarding this "on-demand" aspect, it's important to understand a concept the Australian Standard Pool Heating Sizing Standard recognizes quite well - that is when the air temperature falls below a certain threshold people simply don't want to get in an outdoor pool no matter how warm the water due to the wind chill factor. It's partly why the above mentioned Aus Stand doesn't recommend over-sizing a heating system past a certain collector size. A lot of people don't realize this and choose a heat pump option (or gas) thinking it's on demand right? Sure I'll pay for it through the nose, year in year out no less, but I can warm up the pool and swim whenever I like - well technically yes, but keep in mind that fact; not many people want to get in a pool when it's cold and windy out. And when it's warm out, solar pool heating systems work great, even in party cloudy weather there is still significant solar radiation around as long as the roof air temperature is warm. This concept dramatically reduces this whole "on-demand" disadvantage aspect of a solar pool heater. So if you're after an almost "on demand" type of pool heating experience with solar - that is, heating when it matters most; when it's still at least just warm enough to get in the pool - just size the collector area up a bit.
Spherical Tubes vs Panel Type Solar Pool Heater Collectors
So let's take a look at the various class of solar collectors. Basically, unglazed collectors all fall under two main types* - spherical tubes and monolithic panels or a hybrid mixture of both.
* Glazing means a transparent cover. Glazed collectors are great for higher temperature applications like solar hot water type systems, but are a terrible way to heat a pool for a number of reasons we won't go into here.
Comparing Solar Pool Heater Collector Efficiencies
Let's have a look at all§ the design factors that actually impact collector efficiency. This will help you see through all the marketing fluff (written by Dr Gregory Grochola - thermodynamics physicist).
§ excluding glazing, back insulation and/or surface emissivity/absorptivity treatments - none of which is practical or economical for a pool heating panel.
Collector Design Feature
Why it's Important
Range of Values
Water flow rate: some collectors are limited by small bore tubes
Higher rates helps strip heat from the collector face; collectors work at a higher efficiency point
1-10 L/min/m² - diminishing returns past 10 L/min/m²
Thermal conductance of polymer material: higher the better
Helps heat diffuse faster into the water; collectors work at a higher efficiency point
0.19† W/(m K) for PVC
0.11-0.22† for PP
0.42-0.51† for HDPE
Material thickness: lower the better, but durability must be considered
Lower thickness helps heat diffuse faster into the water; collectors work at a higher efficiency point
1.5mm to 3mm
Hot spot areas: collector surfaces that don't get any water flow
Hot collector areas will bleed heat to the atmosphere and hence cause inefficiency
Some collectors have large gaps between tubes - some no gaps
Turbulence of water flow: straight tubes mostly have laminar flow
Turbulence helps heat diffuse evenly into the water; collectors work at a higher efficiency point
Laminar to fully turbulent flow
Low wind permeability and surface turbulence
Low permeability reduces wind conductive losses at the surface on cooler days
Loose tubes to solid flat face collectors
Flat face: minimum shaded areas
A flat face reduces radiative surface losses
Curved tubes to solid flat face collectors
And that's it! Forget all the marketing fluff, what you want in terms of efficiency is a collector with good polymer thermal conductance, moderate face thickness (considering durability), no hot spots, fast turbulent water flow and a flat collector face. You can now easily compare other collector designs and see which aspects they have. We estimate that the best collectors are about ~50% more efficient (in the shoulder months) than the worst collector designs, which corresponds to 33.3% less roof space requirements. But keep in mind, efficiency is only one aspect to consider; a low-efficiency collector can easily be as effective as a high-efficiency collector, you just need a larger area.
Comparing Other Pool Heater Collector Design Aspects
Apart from efficiency below is a comprehensive list of things you might like to consider when choosing a solar pool collector type.
Why it's Important
Range of values
Cost per m²
Obviously, cost is a large governing factor
$50 to $200 per m² (supply only)
Durability and warranty period
Will your system last 10 years?
15 to 35 year warranties are out there
You want something that's at least half pleasing on the eye, keep the Misses happy
Largely a matter of personal preference
Age chalking of surface
Consider that some polymer materials are more prone to surface age chalking which will turn the surface grey
Various polymer formulation however, HDPE has the best proven history
Roof space requirements
Again, different collectors have different efficiencies and will require differing roof space areas
~33% less area requirements between the best and worst collectors
Good fit for a roof space
Some collector shapes are just an awkward fit, PVC tubes shine here as they can conform to and fill any roof space
Fixed size panels - to fully conformable systems like PVC tubes
Potable polymer construction
You and your family's exposure to plasticizer (phthalate) chemicals should be a large consideration
A variety of polymers are out in the market place
Cockatoo and vermin proof
Last thing you want to do is install a tube type system in a cockatoo prone area, you'll be up there every year fixing holes
Vary of susceptibility, from cockatoo prone to completely resistant
Imagine you've just installed your brand new PVC tube system and you get hail the size of golf balls the next day
Depends on the size of hail, stiff impact resistant polymers are best
You might be in a cyclone area, PVC tubes are notorious for becoming unstuck and blowing off a roof if not installed properly
Various levels of windproofing is available, look critically at strength, density and longevity of fixtures
Frost prone area
Are you in a frost prone area?
Most systems should be frost proof
Ease of installation
Is the system DIY or does it require special skills?
Range of systems are out there, tile installs are more difficult
Roof attachment means
Roof perforations may leak, while glue down systems may get blown off a roof with age
Ranges from glue down to roof perforations
Likelihood of leaking
Leaking will rust your gal roof and/or gutters and you won't know about it for a while, definitely something to consider
Largely dependent on collector design but also system pressures, higher system pressures are more prone to leaking
The difference between two collector designs can pay for the initial supply cost of the system over the systems lifetime!
Range of pump powers, open channel large bore collector are best
Comparing Solar Pool Heating System Design Aspects
So we've compared collector efficiencies and collector design aspects, what about actual system design aspects.
System Design Feature
Why it's Important
Range of values
Independent, manual/motorized or booster type plumbing system: Do you have independent solar suction and return lines?
Different plumbing setups work differently and you want something that matches your lifestyle and budget (see below for more)
$100 for a simple manual set up, up to $1000 for a booster or motorized ball valve + controller system
Quality of controller
Consider build quality and reputation as you want a reliable trouble free system
Various qualities are out there but the ones that have stayed in business are all pretty good
Does the system require winter cycling
Do you want a system that has to run over winter?
Some collectors need winter cycling other don't
Do you need tropical mode
You'll know if you need this or not
Not all controllers have this feature
Do you need frost protection
If you're in a frost prone area you might like to protect PVC pipes (or some collectors) as they are not frost proof at all
Not all controllers have this feature
Quality of pump
Obviously, you want a reliable efficient and quiet pump
Range of qualities are available from cheap Chinese brands to better quality brands
Different system running costs
These can be substantial for some dual pump systems
Independent systems with small pumps are best, dual pump booster systems are worst
Support Australian Made but only if it's the best option
Some components are some aren't
Getting a Cost Estimate
So you've decided on a specific solar pool heating system and now you want a cost estimate, here are the specifics you'll need to consider.
1) Should I DIY or Use a Solar Pool Heating Company/Installer?
Possibly the largest cost consideration is going to be whether or not you DIY or get a pool heating company or installer to quote on an installed system. Due to the seasonal nature of the work this can get very expensive. Depending on system size and the amount of plumbing required you can budget about $1,000- to $3,000 just for labour and installer mark-ups on supplied components (and installers will push their components due to the marks ups they get). So is it worthwhile taking some time for a DIY project? We've seen and heard about a number of overpriced, shoddy, low quality component installs to say absolutely, if you are able to do it safely you should seriously consider DIY. You can source the best quality components from reputable suppliers (here we only sell the best) and you'll have full control over how the system is installed. Make sure a supplier has extensive manuals to guide you and many years of experience to answer any technical questions you may have during installations. You'll end up owning a higher quality more reliable pool heating system for less money sometimes than inferior competing kits AND you'll have better quality install that you'll know how to service.
Consider Quality of Work, Components and Roof Fixing Methods
It's understandable why shoddy installs happen sometime; pool heating installations are seasonal, full-time installers wait around all year then all of a sudden they get bombarded with more jobs requests than they can handle so they feel they can charge an arm and a leg and be picky with their jobs. Companies and installers then need to take on part-time workers that may not be well trained, and they are rushed and under pressure to finish the job fast. If there are complications, installers have no motivation to take their time and do it properly to make sure the system will last as they are not paid by the hour. Most of the shortcuts they may use appear many years down the track typically with no recourse for the consumer.
We've seen competitors use self-tappers or rivets as fixings on metal corrugated roofs as that's the easiest and fastest thing to do. In 5-10 years these superficial metal to metal fixings are likely to corrode drill holes and are likely to pull out in a strong wind storm. The only proper metal roof fixing method that we recommend (as stated in Solar PV Australian Wind Loading Standard) are long roofing screws, sunk deep into battens or rafters. We've seen other companies drill tile perforations for fixings that in time are likely to leak water down the screw onto the batten. We only use non-peforating solar roof hooks as standard tried and tested tile fixings in the PV industry. In terms of other hold down fixings we see some competing products use glass filed plastic fixings which are subject to UV degradation - after 10 years of baking in the hot Australian sun what level of strength will these plastic fixings retain? The only plastic that has a proven long term pedigree in the sun is polyethylene. Our philosophy is that fixings must last the entire life of the system.
An Important Note on Safety
Having said all of that; you should only consider DIY if you're confident of performing the work safely. If you need to get up on a pitched two story roof and you are not 100% confident, best leave it to the professionals, as you should never underestimate the chance of a fall. If you can't DIY try to source a trusted installer - at the very least go with a company with good component and installation quality control standards.
2) Sizing Your Solar Pool Heater - What Kind of Season Extension Should I Aim For
It's important to understand the limitations of solar pool heating, as mentioned above solar pool heating is not an "on demand" system, however if sized higher it can come pretty close to an "on demand" system, by virtue of the fact that it works well when the air temperatures are still warm enough to get in a pool, while almost no level of heat pump or gas heating is sufficient to entice people to get into a pool in windy cool conditions. In the industry we talk about "season extension" months. The Australian Pool Heating Standard recommends about a 3 month extension. What this means is that you'll get the same pool water temperature 1.5 months earlier in the season and 1.5 months later in the season with solar heating. We recommend sizing can range from a minimum of 2 month extension; as some people really just want to swim in the summer months - to a 4 month extension for people that use the pool more frequently or want to swim at night, and hence want that almost "on demand" pool heating experience.
When sizing a new system there are a number of factors to consider. We provide an interactive sizing calculator that takes into consideration almost every imaginable factor, see below. This calculator is based on minimum Australian Standard pool heating sizing and will include weather, solar sunlight hours per postcode, combined with installation specific factors to come up with the best possible sizing for your budget. It gives sizing advice for PVC strips and panels.
Professional Solar Pool Heating Sizing
It's important to factor every aspect affecting a pool's temperature, as some pools can suffer from a number of cumulative cooling factors, for example our calculator instantly assess:
- Your postcode location
- Roof pitch angle of the installed collectors
- Roof facing compass direction
- Your pools total water surface area
- Whether or not the pool is sheltered from the wind
- Shading on the pool during the shoulder months
- Local / Regional weather factors
- Whether it's an indoor or outdoor pool
- Your roof type
- Manual or Automatic system
- Depth of solar suction ports
- Color of pools wall surfaces and floor
- Whether it's an in ground or above ground pool
- And finally your budge and expectations
Surface Area of More Complex Pool Shapes
To work out the surface water area of odd shaped pools use the following trick:
- Measure the pool's edge to edge length.
- Draw an imaginary horizontal line cutting the top edge of the pool so that the dark blue shaded areas above the line are approximately equal to the red areas below the line. You can eyeball this quite accurately, then mark it.
- Now do the same for the bottom side, then finally measure the width distance between these two eyeballed lines.
3) System Plumbing Options
Next thing to consider is what kind of plumbing system you want to set up. We always recommend Independent Systems, see definitions below. These systems run a small independent pump, typically for 8 hours per day and are actually more energy efficient than systems running through the main filter pump which have to run the large filter pump for 8 hours per day just to pump the solar side. Of course independent systems require separate solar suction and return lines, whereas for older pool these might not have been installed. If that's the case you'll need to go with a plumbing configuration that taps into your existing filter return line to divert water to your roof. There are a few configurations that can be chosen, see below or one of our pool heating manuals. Most people that do not have independent solar suction and return ports will choose a Manual/Timer System and place the main filter pump on a timer to run during the warmest part of the day. These manual systems can be automated down the track. We have three class of listings:
- "Automatic Kit" - can be used to set up an Independent System or Integrated-Independent System - includes a solar controller (pump sold separately)
- "Manual Kit" - runs through the filter lines, can be used to set up a Manual/Timer System with a 3-way and non-return PVC ball valve (can be motorized/automated later)
- or just collector "Replacement Kit" - for people that just need to replace their old PVC tube collectors on the roof
If you need to set up a specialized system like for a Booster/Retro Fit System (requires AquaSmart 5 FS or CD controller) or the Motorized Ball Valve System (requires AquaSmart 5 AV controller), please contact us at EcoOnline.
4) Solar Pool Heater Pump Sizing
If you're considering installing an independent or retro/booster type system you'll need to consider solar pump sizing. If you're purchasing a new pump make sure it's specifically suited for solar pool heating systems, as pool filter pumps are geared differently. In terms of sizing, a grossly oversized pump could not only limit collector lifetimes, but will cost you more in electricity usage (literally thousands of dollars over a systems lifetime!). An undersized pump conversely will limit collector efficiencies and not turn the water over sufficiently, resulting in poor system performance. To help you size a pump, we've written quick table guides in our manuals, but if you really want to optimize your pump power saving you can use our panel system pump sizing calculator
or our - PVC strip system pump calculator
- these simulate various pump sizing choices and their respective effects on collector efficiencies and energy savings.
5) Get a Cost Estimate of Our DIY EcoOnline Pool Heating Systems
As you can see EcoOnline.com.au has intimately considered all aspect of pool heaters and has chosen to sell particular systems not by accident, but by extensive research into them. We only sell, develop and support the best systems that are excellent value for money. In fact we won't be beaten on the cost of an equivalent system so just ask. We sell two types of pool heating systems: PVC tubes and OKU panels with an extensive history of longevity in the field. Check out more details on these systems by clicking on the linked images below.
Frequently Asked Questions (FAQs) On Solar Pool Heaters
Q. Will a solar pool heating system work in part cloudy conditions?
A. Partly, yes but only if the air temperature is sufficient and there is enough solar isolation. Keep in mind that pool heaters also heat the ground around the pool. Hence a pool will not completely lose heat in one day of cold weather, although it might be substantially cooler, it'll get back to temperature quickly the next day if there is sun. Eventually, it's the overnight cold air loses that make it impractical to keep heating the pool and the season over.
Q. How many panels do I need?
A. Please use our interactive sizing calculator to accurately size your panel or strip needs, if you have any difficulty please contact us. Note: we frown upon the practice of selling you more panels than what you actually need for your heating goals - to back our smaller sizing recommendation we provide a panel sizing guarantee.
Q. I was sized a much larger rubber mat system - why is your panel area recommendation smaller?
A. Besides the increased efficiency in cooler weather during critical season extension months - we absolutely frown upon the industry practice of selling you a larger system. The Australian Standard 3634-1989 for sheltered pools only recommends 60% (rubber strip) coverage in southern regions, 50% for mid regions, and 40% for northern regions. Over-sizing a system will result in polymer collectors stagnating at detrimental temperatures of up to 80˚C for longer periods during hot days when the controller shuts the system down. As such Over-sizing reduces collector lifetimes, requires a larger pump and higher upfront costs – all for diminishing gains in water temperature. If you require higher temperatures beyond our maximum collector recommendation we recommend a solar blanket.
Q. Can I undersize my system and upgrade as needed later?
A. For panels yes, but only to an extent and we don't recommend it. You should not go below our minimum 2 month extension recommendation, see our interactive sizing calculator. No - we are not trying to sell you a larger system. There are very good reasons why a system should not be dramatically undersized. Effective heating requires a minimum daily turnover typically 50% of your pool water volume. However, there are flow limitations on panels; hence an undersized system may not handle the flow required which could over-pressurize panels or if the flow is insufficient, will result in an unmixed stratified layer of warm water which will cool excessively overnight.
For PVC strip, we have to say no, it's difficult to slice in an extra manifold section into the main manifold pipe once it's all glued up; it's best to size your system right the first time.
Q. Can I use my existing controller and mains power pump?
A. You can use your existing controller if it’s in good working order - however pressure pumps that power rubber mat systems are typically too strong for these panels. Over-sizing the pump not only uses more electricity but has the potential to limit panel life times due to large pressure fluctuations in the panels. EcoOnline (and OKU) only recommends typically 0.25HP to 0.5HP pumps for small 8 to 30 panel systems.
Q. Can I use my filter pump and save electricity by not installing a second pump?
A. It is a false economy to use a large filter pump for solar applications – the pump still has to expend energy to pump water to the roof, putting back pressure on the pump reducing filter flow, hence there is no free energy gained. Besides this we don’t recommend running a high power filter pump for 8 hours per day for the solar side (potentially over pressurizing panels) if you don’t need to filter for that long. An independent system with a well matched small pump will save you money in running costs and look after your panels in the long run.
Q. Can I use a low energy usage variable speed pump?
A. No, after witnessing customers try such pumps and struggle with them our advice now is not to use them, unless they can be set to run at a constant speed without a start up surge. We find variable pumps start at full power then taper back, this puts a lot of pressure fluctuations through the panels on start up which could limit panel lifetimes. We only recommend pumps that can pump at a constant set pressure.
Q. I don't have independent solar lines installed on my pool can I tee into my main filter pump suction line?
A. Generally we don't recommend this as you may have priming issues with your main filter pump during start up due to air been drawn in from the solar line tee you installed. Whether your filter pump will deprime in this case will depend on how far below the waterline you installed the solar tee. Note, a non-return on the solar line will not help here as non-returns are not generally air tight over time. If you do not have independent solar lines and can't install the tee far below the water line (minimum say 1m below) then your options are a manual system, a booster system or a motorized ball valve option, see manual for plumbing diagrams.
Q. Do we have installers?
A. At present unfortunately no we do not have installers as we ship around Australia. However, our manuals are very comprehensive and cover most situations and issues. There is also unlimited tech support available. Most handymen/tradespeople can install our systems. From what we hear, solar pool heating installs are very seasonal, hence most specialist pool heating installers are run off their feet during the install season, this means they charge an arm and a leg for poor rushed installs. Our advice is if you can DIY safely or source a trusted installer that will take his/her time, you will save a great deal of money and headaches.
Q. Can I download your comprehensive manual before I purchase?
A. Yes, in fact we highly recommend you check over the manual to get a good idea of installation requirements before you purchase. The manual can freely be downloaded from our EcoOnline download page.
Q. Is this system easy to install for tiles?
A. OKU panel installation on tiles are more difficult and we recommend should only be attempted by experienced DIY or tradespersons. PVC strips are easier to install on tiles. (Please note safety notice when climbing up on a roof.)