ThermoPower™ 20 Tube Evacuated Tube Collector

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Experience unparalleled solar efficiency with SunMaxx’s 20 tube evacuated solar hot water system. Featuring 1″ NPT connections and backed by a 10-year warranty, this OG-100 certified system is compatible with both drainback and closed-loop configurations. A trusted product since 2006, it offers a sustainable solution for your hot water needs.

SKU: ThermoPower-VHP20 Category:


Evacuated Tube Collector ThermoPower™ VHP Series

The Evacuated Tube Collector from SunMaxx Solar is the perfect choice for both the do-it-yourself customer and the professional installer. This solar hot water heating system is an all-in-one package that comes with the necessary components and is designed to be cost-effective and easy to install. The Evacuated Tube Collector works with a manifold of tubes that transfer heat from the sun to the water, making it highly efficient when compared to traditional hot water heating systems.

It also requires minimal maintenance, making it a great long-term option for your home. The Evacuated Tube Collector is the perfect way to make your home more energy-efficient and reduce your bills at the same time.

Superior Performance

SunMaxx’s Evacuated Tube Solar Collectors offer exceptional efficiency and cost-effectiveness, particularly in colder climates. Unlike other solar collectors, these tubes are freeze-protected, maintaining efficiencies of over 70% even in freezing temperatures. Additionally, their unique design allows for high efficiency even in low-light conditions, making them an excellent choice for winter use.

Designed to provide hot water for a variety of applications, SunMaxx’s customers use their collectors for domestic hot water, radiant heating, and pool/hot tub heating at residential, commercial, industrial, and municipal locations around the world.

SunMaxx’s Evacuated Tube Solar Collectors are also the most affordable and cost-effective option on the market today.

Features & Benefits

  • High operational safety
  • 92% coating absorbance
  • Suitable for flat roof
  • Adjusted to mount and connect to large solar installations
  • Tilt angle up to 75 degrees
  • Ready mounting system provided
  • 10 years performance warranty
  • 25-30 years expected lifetime
  • SRCC & Solar Keymark Certified
  • Free technical support

Quick Sizing

Calculators & Guides

Technical Details


  • Weight: 170 lbs (without crating)
  • Dimensions: HxW 79in x 70.2in
  • Packaging: Ships via freight on a pallet or is available for local pickup (1 pallet is available for residential or commercial delivery.)
  • Assembly Time: A collector can be assembled in 1.5 hours
  • Manufacturer: SunMaxxSolar
  • Warranty: 10 years collector warranty
  • Expected Lifetime: 25-30 Years
  • Fitting: 1″ Male NPT


  • Standard Flush and Tilt Mounting Frame
  • Manifold (header)
  • 20 Revolutionary SunMaxx Evacuated Tubes
  • 20 Copper heat pipes
  • Hardware required for collector assembly

ThermoPower™ VHP  Series Details:

  • Tube Length (in)/(m) 70/1.78
  • Outer Tube Diameter (in)/(mm) 2.2/56
  • Inner Tube Diameter (in)/(mm) 2.1/53.3
  • Tube Material Borosilicate Glass
  • Tube Coating AlN/Al.
  • Thermal Expansion (in)/(mm) 3.3*106 / 84*106
  • Coating Absorbance > 92%
  • Coat Emissivity < 8%
  • Vacuum (Pa) < 5×103
  • Heat Loss (W/m2.oC) < 0.7
  • Max. Pressure Thrust (MPa) 1.0
  • Flow Rate per Tube (gpm/lpm) 0.028 / 0.11
  • Tilt Angles (degrees) 15-75
  • Orientation Portrait
  • Max of Tubes in series 210
  • Operating Pressure (psi)/(bar) 2070/1.44.8
  • Maximum Pressure (psi)/(bar) 150/10.3
  • Stagnation Temperature (F/C) > 428/220
  • Heat Transfer Fluid Water/Glycol
  • Heat Transfer Method Heat Pipe
  • Manifold Socket Soldered Dry Socket
  • Glass to Metal Seal Type Hermetic
  • Fittings 1” Male NPT

Model  Details:

  • Dimensions (in)/(m) (WxH) 70.2 x 79/1.73 x 2.01
  • Gross Area (ft2/m2) 37.42/3.476
  • Net Aperture Area (ft2/m2) 21.41/1.989
  • Absorber Area (ft2/m2) 18.39/1.709
  • Weight (lbs/kg) 170/77.1
  • Fluid Capacity (gal/L)  0.4/1.51
  • Rated Flow Rate (gpm/lpm) 0.56/2.12
  • Minimum Flow Rate (gpm/lpm) 0.3/1.14
  • Maximum Flow Rate (gpm/lpm)3.4/12.87
  • Storage Tank Size (gal/L) 5060 / 189.3227.1
  • SRCC Clear C Rating (kBTU/panel/day) 28



  • Domestic hot water: Normal hot water for a house
  • Radiant floor heating: Systems of any size
  • Pool and spa heating: Large and small pools
  • Residential hot water applications
  • Commercial hot water applications
  • Industrial hot water applications
  • Municipal hot water applications
  • Tube Length: the length of each evacuated tube, in inches and meters.
  • Outer Tube Diameter: the outer diameter of each evacuated tube, in inches and millimeters.
  • Inner Tube Diameter: the inner diameter of each evacuated tube, in inches and millimeters.
  • Tube Material: the type of material used to make the evacuated tube, in this case, borosilicate glass.
  • Tube Coating: the type of coating applied to the evacuated tube for maximum performance and efficiency, in this case, Al-N/Al.
  • Thermal Expansion: the amount of expansion that occurs due to changes in temperature, measured in inches and millimeters.
  • Coating Absorbance: the percentage of solar energy absorbed by the tube coating.
  • Coat Emissivity: the ability of the coating to emit thermal radiation.
  • Vacuum: the level of vacuum inside the evacuated tube, measured in Pascal (Pa).
  • Heat Loss: the amount of heat lost from the tube per unit of surface area and temperature difference, measured in Watts per square meter per degree Celsius (W/m2.oC).
  • Max. Pressure Thrust: the maximum pressure that can be exerted on the tube, measured in Megapascal (MPa).
  • Flow Rate per Tube: the flow rate of the heat transfer fluid per tube, measured in gallons per minute (gpm) and liters per minute (lpm).
  • Tilt Angles: the range of angles that the collector can be tilted for optimal performance, measured in degrees.
  • Orientation: the orientation of the collector, in this case, portrait.
  • Max of Tubes in series: the maximum number of tubes that can be connected in series.
  • Operating Pressure: the recommended range of operating pressure for the collector, measured in pounds per square inch (psi) and bar.
  • Maximum Pressure: the maximum pressure that the collector can withstand, measured in psi and bar.
  • Stagnation Temperature: the maximum temperature that the collector can reach when there is no fluid flowing through it, measured in Fahrenheit and Celsius.
  • Heat Transfer Fluid: the type of fluid used to transfer heat from the collector to the storage tank, in this case, water/glycol.
  • Heat Transfer Method: the method used to transfer heat from the evacuated tubes to the heat transfer fluid, in this case, heat pipe.
  • Manifold Socket: the type of socket used to connect the manifold to the tubes, in this case, soldered dry socket.
  • Glass to Metal Seal Type: the type of seal used to connect the glass and metal components of the tube, in this case, hermetic.
  • Fittings: the size and type of fittings used to connect the collector to the piping system, in this case, 1” male NPT.

The ability to convert solar energy into thermal energy is expressed by the optical efficiency of the system (ŋ0). The global solar radiation varies considerably from region to region. On a clear summer day approximately 850 W/m2 (270 Btu/ft2)can be expected, whereas clouds can reduce it to 400 Btu/ft2 (127 Btu/ft2)

Both Flat Plate and Vacuum Heat Pipe collectors are insulated to prevent heat loss, but due to extremely good insulation properties of the SunMaxx Vacuum heat pipe Solar Collectors, the “only” heat loss is via the SunMaxx Manifold with its small surface area and thick layer of high-quality polyurethane foam

SunMaxx Evacuated Heat Pipe Solar Collectors can supply heat at temperatures significantly higher than those achieved by Flat Plate Collectors. This comparison is particularly relevant in cold, windy and cloudy climates. The following explanations are for installations of up to 90 tubes (4 Flat Plates).

How to Size your Solar Hot Water System (DHW):

On average a homeowner uses approximately 20 gallons of hot water per day per person. Using this figure you can calculate which size prepackage system is suitable for your heating requirements.

If you are looking to utilize a solar hot water heating system for space heating needs please contact our solar hot water sales department so we may provide you with an accurate assessment of your heating requirements. Typically we are able to offset between 40-80% of your home heating needs with a payback period of less than 8 years.


Need Assistance?
If you have questions need help or simply feel uncomfortable placing your order online feel free to contact the product representative at 1-800-786-0329.

While both types of collectors capture the suns energy and convert it to hot water each have there own advantages.

Evacuated Tube Collectors are best used in northern climates where freezing can occur and can be utilized in areas where temperatures drop down to -60°F. Evacuated Tubes are are extremely efficient by virtue of the Tubes themselves. Each Evacuated Tube is hermetically sealed meaning it is highly insulated due to the fact that it is a sealed atmosphere nearly impervious to outside temperatures. Evacuated tubes can also be replaced if damaged, simply by plugging it in, no need to replace the whole unit.

SunMaxx Flat Plate collectors use a highly efficient flat absorber material called Tinox which transfer heat to a series of copper tubes which circulate a 50% glycol/water mix. The collectors themselves are in essence a a sealed insulated box which captures the suns energy and transfers it via the Tinox, then through the pipes filled with glycol and into  the storage tanks.

Yes you can. Collectors can be attached to our ballast system, which uses the weight of standard patio blocks to hold the collectors in place. Wind load calculations must be done by an engineer to conform to local building codes. With the proper weight attached, collectors will stay in place without putting any holes in the roof. This has been done with our evacuated tube collectors and our flat plates. Flat plates obviously have a much higher wind resistance, and therefore require greater weight to hold them in place. Our ballast system will work with photovoltaic panels as well.

There are no guarantees with rafters when it comes to distance apart or consistency. The easiest way to deal with this problem is using the ConnectMaxx rail system. Our roof mounts can be secured where the rafters are, and then our rails can be secured to the roof mounts. All of our collectors can then be secured anywhere along the rails using sliding blocks. When using SunMaxx rails, you can worry less about where the rafters are and more about where you want your collectors!

This answer depends on what you are trying to accomplish. For simple Domestic Hot Water systems you should try and position you collectors at the same angle as your latitude. For systems that are tied into the home heating system, as in a combisystem, you should position you collectors 15 degrees higher than your latitude. For summertime use only systems, as in a pool system, you should position your collectors at your latitude minus 15 degrees.

For systems that have a high solar fraction, i.e. 75% or greater, you should increase the angle of incline in order to decrease your summertime production slightly.

Do you want to make this system perform to its highest ability or should it look nice and fit the architecture of the house?

We have all seen those albatrosses on the roof that are cantilevered at a compound angle to get a few extra BTU’s at the cost of aesthetic appeal. Here are some guidelines to consider when deciding what is most important in determining collector orientation and inclination.

For most collectors, tubes or flat plates, the angle of inclination has a 30 degree window of variation and the performance will still be within 95% of the expected maximum. That is, if your collectors should be mounted at 55 deg then you can mount them between 40-70 while losing only a small fraction of energy gain.

As for the collector orientation, that window is 60 degrees for Evacuated tubes and 30 degrees for flat plates. These considerations allow you to fit the collector to most homes’ pitch and orientation without losing too much energy gain.

Obviously you want your client to get the most out of it, but you are more likely to get additional jobs if the collectors are mounted in a way that takes into account the aesthetic appeal. Ask your Sunmaxx Representative for a copy of the Inclination and Orientation performance Chart so you can make informed decisions.

Yes it is. Depending on your type of collector, you can program your controller to manually activate the circulator which will bring heat from your storage vessel and into the collectors, which will radiate that heat back out thus melting the snow. This method only works for FLAT PLATES however and will usually take as much energy as it makes. When the sun is out in full force, the rays passing through thge snow are typically enough to create substantial heat that in turn, melts the snow on flat plates.

For Evacuated tubes however, there is very little you can do to melt the snow. If your collectors are sitting at a tilt off from the roof pitch, you should be okay because the snow will pass between the tubes onto the roof. But for flush mount EVT systems, snow can and will build up. However, in my experience, this will only affect the output for a day or two. Becuase if the sun is out enough to make any amount of BTU”S then there will be enough heat wasted at the roof/collector interface that begins to melt the snow alowing it to slide down from the top of the tubes. With only minimal exposure to the direct sunlight, the small amount of exposed tube will begin to yield significant amount of BTU’s, even though they are mostly covered. So for tubes, dont sweat it, you are not going to lose much unless of course they get covered by a couple feet or so then perhaps you’ll want to sweep them off if you can.

This will be a debate well in to the future. For an more in-depth review please watch this Click here to watch this 1/2 hour webinar. Your decision should be based primarily on the following considerations:

  • Temperature demand– What is you existing application? EVT’s will outperform FP’s at higher temp load.
  • Climate location- In a general sense, flat plates have more value than evacuated tubes in warmer climates and EVT’s will do better in cold, cloudy climates.
  • Aesthetics appeal– This is where there is no “right” answer. Instead, each person has their own personal view. We recommend that you go with it. If they prefer flat plates for that reason then you install flat plates and if they prefer evacuated tubes for their aesthetic appeal, then by all means, you should install Evacuated tubes.

The point is, you really CANT GO WRONG. Each type will yield significant value and in the end, the differences will be negligible.

Fortunately, solar thermal collectors are not nearly as sensitive to light conditions as PV collectors. As for performance, you have roughly a 60 degree window of opportunity to mount the collectors toward south before you begin losing a small bit of total production. In other words, your house can be situated 30 to the east of true south or 30 degrees to the west of true south and your performance will still be at or above 95%.

As far as tilt angle goes, this window opportunity is slightly smaller but still you can have a roof pitched about 20 degrees plus or minus of your particular latitude angle and you will still see results at or above 95% of expected.

Ask a SunMaxx rep to run a Polysun report for your particular conditions to be sure, you will be happy you did and pleasantly surprised.

SunMaxx Solar collectors have the below certifications and standards.

  • SRCC OG-100
  • USEC UL 1703
  • ASHRAE Std 93-1986
  • ASTM E 330 (Wind Load Rating)

SRCC OG-100 Certification

Replacement Evacuated Solar Tubes

We recommend the below accessories.

[porto_products use_simple="" ids="12999, 13000"]

Replacement Evacuated Solar Collector Parts

We recommend the below accessories.

[porto_products use_simple="" ids="21347, 21349, 21351"]

Collector Connection Accessories

We recommend the below accessories.

[porto_products use_simple="" ids="18446, 18447, 21353, 13109"]

Evacuated Tube Collector Accessories

We recommend the below accessories.

[porto_products use_simple="" ids="18817, 13063, 18815, 18804, 21356"]

Evacuated Tube Collector Mounting Accessories

[porto_products use_simple="" ids="21622, 21625, 21626, 21634, 21631, 21633, 21635, 21640, 24013"]

Solar Collector Warranty: 10 years

Extended Warranty: Available for purchase with qualified SunMaxx Solar installer.

SunMaxx Solar Collectors Warranty

How to Order:

If you are confident with your solar hot water heating requirements you can place your order online by clicking on the add to cart button which is located above. All orders are reviewed by our solar hot water heating department and the customers are contacted in order to ensure that you have ordered the correct merchandise for your application. In the event you have any questions our sales staff are available from 8:30AM to 5:30PM EST.

Silicon Solar Inc ships products internationally please ask your sales representative for a shipping rate to your destination.

Need Assistance?
If you have questions need help or simply feel uncomfortable placing your order online feel free to contact the product representative at 1-800-786-0329.

Additional information

Weight91 lbs
Dimensions45 × 21 in