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flat roof solar

Powerstrips on a flat roof.

PV and pool solar

Powerstrips on a tile roof fitted around a PV system.

pool solar on tile

Space optimized-no roof penetrations

Solar pool heaters are no longer just plastic black rectangles strapped to the roof of a house with non-structural roof penetrations. Today's technology allows these systems to be fitted to the roof space and secured structurally often with no roof penetrations at all. Powerstrips, manufactured by Hot Sun Industries of San Diego California are freeze tolerant, serviceable, modular and repairable. Fitted tighter to the roof than rigid sheet polypropylene solar panels means less wind loss and better performance per collector area all without sacrificing the value of the home.

solar types compared

Powerstrips vs other types.

solar hidden on a pergola

Powerstrips hidden on a pergola.


We believe that solar heaters need to be flexible. Most importantly flexibility means the solar panel can freeze solid full of water. A black heat exchanger with the clear night sky will freeze at 42F not 32F. The solar collector operates below air temperature at night. During the day, if there is no water flow the solar collector will be much hotter than the air. This is heat transfer by radiation either way. So the solar collector needs to be flexible otherwise you have to make sure it is fully empty every night in the late part of the season. That means a typical rigid 4x12 polypropylene solar collector must be sloped to drain (can't use it on a flat roof) and the system pressure must be low enough to allow drainage and water has to be able to pass through a sealed 3 way valve. "Solar valves" allow this drainage through a small built in check valve. We don't like to rely on that and we don't have to because our collector is flexible. We don't like the idea that one mistake and you have to buy new solar collectors. Flexibility is also important in that the solar surface can flex. Rigid polypropylene strap down grid style solar collectors have to move around on the roof as their manifolds expand and contract with temperature. This side to side movement can easily be 2 inches. The entire sheet has to go along for the ride under straps that only allow for 1/2" of movement. (Limit the size of a bank to 5 collectors when using polypropylene 4x12's) With our flexible collectors they just flex. No shuffling around under straps. Flexibility also allows our collectors to be glued directly to tile roofs. No roof penetrations are required and our system is rated for maximum hurricane code resistance without a single roof penetration. Powerstrip is the clear best choice for tile and flat roofs.


We've compiled performance charts for many areas around North America and verified them with hundreds of real solar heated pools. Click on your region to get an idea of what solar can do for a pool in your area. See the section on the navigation bar called "Regional Performance Curves".

Below is is a typical pool in San Diego, California with a little pool shade, located near the ocean where the collectors are on a south facing roof.

solar heater performance chart San Diego

100% solar means a solar heater sized at 100% (same size) as the top surface of the pool.

Go to sizing for the recommended amount of solar for any given pool. Then go to the section of this web site designed for the roof type solar will marry to and you'll find most of the information you need. If you'd like to call us at 858 683 0800 please gather this information first.


Powerstrips were originally developed specifically for tile roofs. The flexible material follows the wave of the tiles to some extent. The system is built on the roof to fit the roof making best use of available space and creating a system that adds value to the home instead of taking it away. One foot wide sections fit each row of tiles meaning that the ends of the tiles are exposed so when you look up at it from ground level you see the ends of the tiles. No roof penetrations, best use of available space, best esthetics, and easiest hurricane rating approvals make Powerstrip the only choice for a tile roof mounted solar pool heater. More on Powerstrips on tile roofs


You can not use a regular polypropylene fixed size collector on a flat roof for 2 reasons. The water won't drain out of it so it'll freeze and burst. Secondly, you have to bolt down that rigid "sail" so it won't fly off the roof. Don't make a roof penetration on a flat roof.

Hot Sun's Powerstrip flexible solar collectors are often secured with a ballasted framework. We developed this system for commercial installations. It can be removed easily for roof resurfacing.

Take a look at these flat roof installations.


Any solar panel can go on a pitched shingle roof but Powerstrips aren't restricted to standard sizes.

Another important advantage we have on shingle roofs is that we can secure both header and footer manifolds to the roof. Polypropylene grid style collectors have to dangle under straps because one header has to be able to move to accomodate the collector shrinking with temperature drop. Flexibility allows Powerstrips to just stretch.

Headers can be arranged vertically and the fin tubing (absorber) glued down sideways via "glue strips". We can't get away from roof penetrations on shingle roofs but we can take away the movement associated with grid style collectors and in doing so eliminate the cyclical stresses on the roof connections.

For more on shingle roof installations see shingle and metal roof installations


Photovoltaics are everywhere these days. They are taking up the space we need for pool heating. Its simply false that solar pool heating can be moved to a lesser solar space like the north facing roof to leave room for the new PV system. PV/Thermal is the holy grail of all things solar energy because PV panels operate far hotter than they are supposed to. They are black and in the sun and they even have a layer of glass over them to ramp up the temperature even more. That electricity you were promised was promised to you at 25C normal cell operating temperature but normally PV modules operate a lot hotter than that. So much so that output can be 12% less than promised or predicted. Not so if we cool the PV panels with the pool heater. Its a perfect match. We need about the same size solar pool heater as you do a PV system and they need to be in the best solar space, the south and west facing slopes. We have the technology to adapt our solar pool heating heat exchanger to the back of your PV array. We get better performance in windy conditions than if we're not behind the PV panels, we improve PV output and we reduce degradation of the PV cells due to heat. Instead of 20% degradation in 25 years we expect 5%. Now you don't see the ugly pool heater just the pretty PV panels. There are permitting challenges because the standards are still being written and there are many competing technologies. Ours is best for several reasons. Its a retrofit so it works with any existing PV array. It can use roof space and PV space not just one or the other. All connections are serviceable outside the PV array. Our system is continuous across the entire bank of PV modules and we achieve a full thermal connection of our surface to the back of the PV modules meaning significantly better heat transfer. We size pvt systems one to one compared to regular solar pool heaters directly exposed to the sun.


A separate solar heater that doesn't involve the roof of your home has appeal but it takes up real estate and you may not want to look at it. Powerstrip solar collectors are not constrained to the normal 4x12 and 4x10 sizes. We can build a structure to fit the landscape. In fact, in many cases it makes sense to mount the solar collector system right to the earth. This option is especially attractive when the ground space is steep.

We can double up the header manifolds at each end eliminating the spaces between the one foot wide sections. This means the solar collector itself can act as weedcloth and we can pack more solar into less space. More on ground mounting and rack mounting.

Hot Sun solar hot swimming pool

Click on sizing to learn all about what to expect from a solar heater. You'll find a form you can fill in so we can help your local dealer fully specify and quote your installed solar heater. If you want to contract this out yourself or install it yourself we specialize in providing the expert support you need.

Hot Sun Industries Inc.,

San Diego,


Note we have representatives in many regions and our products are easily shipped.


Before phoning
please measure the pool and roof and gather the information we need to assist you in pricing. Click sizing for a list.