Will hail damage the collector?

Collectors are constructed and rated to withstand hail up to 1.38 in  (35mm). See Glass Quality/Hail Rating for a more detailed discussion.

How much does it cost?

For a small domestic hot water (DHW) system that utilizes your existing hot water heater, plan on $1000 for an 8 tube collector and $1200 to $1500 for the pump station. Also allow $200 to $1000 for additional hardware like copper pipe fittings, insulation, roof flashing, etc. Installation labor costs can range from 50% to 150% of the equipment total.

For a larger domestic hot water (DHW) system, substitute a 16 tube collector for approximately $2000. The other costs will be similar.

To provide space heating for a home, a considerably larger system will be required with careful system design. 

Solar hot water qualifies for a 30% federal tax credit and your local utility may provide additional incentives. See rebates.

What is the payback or return on investment?

Half as long as PV but still on the order of 5-7 years when compared to heating with electricity. It depends on usage and cost of energy. What is the payback on a conventional water heater from Home Depot? None - you just pay and pay and pay. What is your energy independence worth to you? It should be "priceless".

Collector Sizing

For domestic hot water (DHW) we typically use 4 tubes per person, which assumes 20 gal/person/day usage rate and raising the water temperature from 55F to 120F at a minimum. A 2 person family would need a Seido 8 tube collector and a 50 gal storage tank.  A 4 person family needs a Seido 16 tube collector and an 80 gal tank. The 16 tube collector is just over 6 ft wide (75.6") and about 7 ft long (83").

Storage Tank Sizing

There are several factors that influence tank sizing for solar domestic hot water systems. Most importantly are daily hot water requirements and balance of systems considerations.

Generally speaking, it is prudent to allow 20 gallons for each member of the household.  Remember, in a single tank system, the tank acts both as a solar storage reservoir and a back up heat source. It is for this reason that a larger tank would be recommended. The advantages of a larger tank are twofold: Extra volume of hot water could potentially meet your needs on one or more subsequent cloudy days.  More storage also tends to mitigate overheating issues in closed loop systems. Storage volume that is too large on the other hand will have difficulty reaching the desired temperature, and has diminishing returns with respect to system efficiency and cost.

When considering solar collector sizing, we recommend 2 gallons of storage for each square foot of evacuated tube collector area.  For flat plate collectors, use 1.5 gallons of storage per square foot of collector area. These are guidelines and may be adjusted by your installer to suit your circumstances. 

For space heating and commercial applications, a careful system design must be accomplished as general sizing guidelines are not appropriate in these cases. 

Can I heat my house with these?

Yes, provided that the home is well insulated, thereby having a low heat loss to the environment. There are no rules of thumb for sizing a space heating system based on square footage of a house. You have to know the heat loss, design temperatures, weather data, and solar radiation available to estimate system size. It will be much larger than the domestic hot water (DHW) component alone.

Is there a potential of overheating?

Yes, any closed loop solar thermal system can overheat if the circulator pump is off during peak sun hours. The pressure relief valve guards against damage to the system components. The tubes will not "blow-up" or break due to high temperatures. However, the glycol fluid can be compromised with exposure to stagnation conditions and system performance will suffer.  The best overheat mitigation is proper collector tilt, sufficient storage volume and a heat dump loop. Drain back systems are generally not prone to overheat issues.

Why does one tube have a straight absorber and the other a bent one?

Seido 1 tubes have a straight absorber. These tubes can be rotated on axis to compensate for non-south-facing roofs. The Seido 5 tubes have a convex absorber providing 20% more surface area. They produce more heat per day than the Seido 1's but cannot be turned on axis and should therefore be used only for true south facing roofs (+/- 10 deg).

Which side of the absorber in the tubes should face the sun?

Regardless of which Seido tube is used, always face the blue side to the sun. It is treated with a selective coating to absorb the most energy from the sun's rays.

How can you tell if you lost the vacuum?

All Sunda evacuated tubes have a silvery coating on the inside at the bottom of the tube. When vacuum is lost, this coating depletes due to oxidation and the tube becomes clear.

What is the life of a tube?

The statistical "mean life to failure" is 15 years.

What is the warranty?

10 years. Click here for Warranty Statement.

How do Sunda collectors compare to double glass wall products?

In evacuated tubes produced by Sunda, the absorber surface and heat pipe reside completely within the vacuum environment, which prevents any deterioration in long-term performance.  This is not the case with the double glass wall tubes in which both absorber and heat pipe are open to ambient air.  Being exposed to air, the absorber plate and heat pipe is subject to oxidation, dust, and moisture, which may lead to degraded performance over time.  These concerns are not applicable to the Sunda design.

How heavy is the collector?

Only 110 lbs for the 8 tube collector, and 220 lbs for the 16 tube collector when fully assembled. Modular design allows one person to easily transport the individual components. The 16 tube collector is just over 6ft wide (75.6in) and about 7ft long (83in).

How are they shipped?

Collectors are crated and shipped by common carrier. Only single replacement tubes can be shipped via UPS. Pickup at our warehouse is available.

Is this technology new?

No, the technology is about 20 years old. The Sunda tubes were developed in Germany by Daimler-Benz Aerospace in cooperation with Sunpu, a Chinese solar energy research company.