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Hills 315L Gas Boosted 22 Evacuated Tubes Solar Hot Water System


PLEASE NOTE: Hills' solar hot water systems business ceased operating in January 2013. To view other manufacturers of solar hot water systems, please click here.


Evacuated tube technology delivers significantly better performance than traditional absorbers on the market today. Their advanced design incorporates tubes that consist of 2 layers of borosilicate glass with a vacuum layer between them. The vacuum acts like a thermos flask, retaining up to 97% of the thermal energy, resulting in an increased efficiency.  The Sun's thermal energy is then transferred to the manifold via the heat pipe located in each tube.
The small amount of evaporative liquid in each tube is super heated by the sun's energy and forms into a gas. The gas  rises to the top of each pipe. Heat transfer then occurs between the pipe and water passing through the manifold . The water is then transferred to the tank.
The cylindrical design of the tubes ensures effective collection of the sun's thermal energy throughout the day.


Hills Solar Evacuated Tubes are frost tolerant and have passed the AS/NZ 2712  2007 Standards for both, Hail & Freeze Resistance. The Hills Solar Hot Water Systems have passed the Freeze Test to –15° C without the need for a heat exchanger or Glycol.


A Hills Solar Evacuated Tube hot water system can efficiently capture this free energy and provide you with up to 80% savings on your hot water heating costs. Considering Australia is one of the sunniest countries on the planet it makes sense to utilize this resource by installing a Hills Solar Evacuated Tube hot water system. Not only will you save money but you will also reduce your family’s CO2 emissions by up to 3 tonnes per year.


Solar System Comprises Following Components


  • 22 tubes solar hot water collector system - includes manifold, evacuated tubes and copper heat pipes
  • 315 litre stainless steel tank - Australian made, designed and owned
  • Eternity continuous flow gas hot water booster (Natural or LPG Gas)
  • Standard frame for flush mounting solar collectors to tin or tile roofs
  • Standard flow electric pump for up to 20m run
  • Resol solar controller
  • Flow rate controller
  • Air bleeder for tube manifold
  • 4 way valve
  • Miscellaneous components - rubber pads, stainless steel straps, screws, bolts etc



  • Hills solar evacuated tube collector and manifold 10 years warranty*
  • Everlast stainless steel storage tanks 10 years warranty*
  • Eternity continuous flow gas booster offer 10 year heat exchanger warranty, 3 years on all parts and labour

Technical Specifications


Product description 22 tube collector
Weight 82 kg
Height of collector(inc manifold) 2000 mm
Width of collector 1845 mm
Surface area of collector 3.69 m²
Absorber area of collector 1.76 m²
Aperture area of collector 2.086 m²
Water that manifold in collector holds 1260 ml
Weight of low pitched roof frame 10.5 kg
Weight of a frame (for flat roof) 11.5 kg
Gas Boost Eternity 26
Gas input 195 MJ/h
water supply pressure 150 to 1200 KPa
Gas connection 20 BSP
Water connections 15 BSP
Ignition Electronic
Gas type Natural Gas/LPG
Electrical supply 240VAC
Energy ratings 5.44
Dimensions 520H x 170D x 350W mm
Weight 16 kg
Storage tank 315 Litres Tank
Size in litres (Actual) 315 (327)
Height 1980 mm
Diameter 580 mm
Weight empty 63 kg
Weight full 390 kg
Hot water outlet 1495 mm
Return flow to tank 425 mm
Cold water inlet 168 mm
Electric cable entry 143 mm
Optional Extras
For pumping over 20 metres run
Angle frame suitable for flat roof - 9 to 27 degree pitch
Angle frame suitable for flat roof - 35 to 67 degree pitch
High temperature tempering valve

Evacuated Tube Features


  • Hills Solar evacuated glass tubes provide superior daily heat output due to the cylindrical absorber always being perpendicular to the sun.
  • Insulation properties of the vacuum in the Hills Solar evacuated tube allow 92% of the heat from the sun to be retained.
  • Heat is rapidly transferred from the copper heat pipe and header to the circulating water from the storage tank, passing through a well-insulated manifold, ensuring maximum solar heat gain.
  • The Rockwool insulated collector manifold, sealed evacuated tubes and freeze-protected heat pipes allow reliable operation even in the coldest areas and on cloudy or overcast days.
  • Due to their cylindrical shape Hills Solar evacuated glass tubes are naturally self-cleaning when it rains and thus don’t lose performance through the accumulation of dirt and pollutants.
  • The internal copper manifold pipe in the Hills Solar collector is 35mm in diameter, ensuring greater water flow and is excellent for thermo siphon systems
  • For both gas and electric boosted systems, the Hills Solar collector uses advanced heat pipe technology to provide not only high solar conversion efficiency but also protection against freezing and leaking of any water through the evacuated glass tubes
  • The stainless steel collector frame provides both strength and long-term corrosion resistance.
  • Easy installation and reliable operation is ensured through automated pump operation, low temperature protection and pre-wired power and sensor leads via the Hills Solar controller.
  • Evacuated Tube Collectors are up to 40% more efficient than standard Flat plate Collectors per square metre of aperture

Everlast 315Litres Stainless steel storage tanks


Australian Made, Designed & Owned


All Hills Solar Systems use stainless steel tanks which have a natural oxide barrier to corrosion. Stainless steel tanks remove the requirement for a sacrificial anode.
A UV stable polymer outer casing provides an attractive finish and eliminates the rust which can occur on the outer casing of vitreous enamel steel tanks. Stainless steel tanks are tough, durable and lighter than their equivalent vitreous enamel mild steel tanks.


Hills Solar offer electric boosted solar systems to sustain the water at an appropriate temperature when radiant heat is low and there is cloud cover and rain. The system comes with a standard 3.6kw bottom element however, can be changed to a 4.8kw element to conform with different State regulations. Positioning of the element ensures you will have a full tank of hot water available.


Eternity Gas Boost


Your new Eternity series not only has an energy efficiency rating in excess of five stars, it only uses purchased energy when required, as it only heats the water when you need it. This adds up to substantial savings when compared to those old money guzzling storage systems that require a pilot light. No more money going up in flames. With the Eternity touch pad option, you control the water temperature and subsequently control your savings and reduce your gas bill.


Suitable for all climates


Hills Solar Evacuated Tubes are frost tolerant and have passed the AS/NZS 2712:2007 Standards for both, Hail & Freeze Resistance. The Hills Solar Hot Water Systems have passed the Severe Freeze Test to –15° C without the need for a heat exchanger or glycol.

Suitable for standard roof


The ideal location for collectors is facing due North, however 45 degrees North West or North East is acceptable with minimal loss of efficiency due to the cylindrical design. Hills provides stainless steel frames that allow the collector to be positioned to make the most of any roof orientation.


No of RECs"Renewable Energy Certificates" for an Installation per Zone over 15 Years


Product Code Electric Boosted Systems No of RECs for an Installation per Zone over 15 Years
Zone 1 Zone 2 Zone 3 Zone 4
GB 250 21 NG 10 250L 21e Gas Boosted 10 Tube Collector 18 18 18 15
GB 250 21NG 22 250L 21e Gas Boosted 22 Tube Collector 30 32 30 26
GB 250 21NG 30 250L 21e Gas Boosted 30 Tube Collector 37 39 37 32
GB 315 21NG 22 315L 21e Gas Boosted 22 Tube Collector 30 32 30 26
GB 315 21NG 30 315L 21e Gas Boosted 30 Tube Collector 37 39 37 32
GB 315 25NG 30 315L 26e Gas Boosted 30 Tube Collector 37 39 37 32
GB 315 25NG 40 315L 26e Gas Boosted 40 Tube Collector 40 44 43 38

Downloads and Manuals



Solar hot water quote



  • Model: GB31521NG22
  • Shipping Weight: 135kg
  • Manufacturer:
    Hills Solar