Relevant Calculations for an Evacuated Tube Solar Collector

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Evacuated tube collectors are an efficient way to take advantage of the sun’s rays directed at your home. This type of collector consists of a set of parallel clear glass tubes. Each tube has an outer tube and a metal absorber tube attached to a fin. The fin has a coating that absorbs the heat and minimizes heat loss. The air space between the tubes is “evacuated” forming a vacuum that keeps the heat from escaping. Evacuated tube collectors can reach much higher temperatures. Because of this they are often the choice for commercial or industrial applications. They are more expensive than flat plate collectors but much more efficient, especially for hot water heating. They can save you money but how much money?

In order to calculate the possible savings you will want to determine some information about how you use energy in your home. These factors assume you are using the collector for hot water heating.

Hot Water Usage (In Order By Most To Least)



Hand washing

Dish washing


Washing Machine


Power Cost in Dollars per kWh (look at your electric bill to get this rate)

Cost of installation of the evacuated tube collector system (include maintenance costs)

Check to see if your state or municipality is offering any rebates for upgrading to an energy saving device and find out if your system would qualify.

Calcuate Your Savings

Once you have assembled this information you will be able to calculate the savings per year for an evacuated tube solar collector.

Total Hot Water Use for year in liters

Hot water power consumption per year estimate (kWh) not

Electricity hot water costs per year ($)

Electricity hot water costs per 20 years ($)

Potential local Solar Hot Water savings over 20 year (kWh)

Total hot water savings

If you know what these savings are and what the approximate payments will be on your system you easily calculate the amount your utility bill will be reduced and the number of years it will take you to recoup your investment in the system. This will give you a good about the feasibility of using this kind of solar collector in your home.