Heat Exchanger - Transfers heat from one fluid to another without actually mixing the fluids. Heat exchangers are required in solar water heaters in Texas because it is impractical to send potable water through the solar panel. This method protects the system from scaling, and also keeps water from freezing in the panel and bursting pipes.

Thermal Mass - Thermal mass is the ability of a substance to gain and store heat. Water has the highest thermal density/thermal mass of any common naturally occurring molecule. It takes a lot of energy to heat water, thus water can store a lot of heat energy for long periods of time. We use this property in solar water heating to store heat gained during the day for use at night. This is also why drainback systems are so efficient, since the heat transfer fluid is also water.

Kilowatt Hour(KwH) - A kilowatt hour or KwH for short, is the most commonly used measure of energy by electric companies. Simply, it means 1 kilowatt of draw for one hour. A practical example in a typical electric water heater with a 4.5 Kilowatt element means that running an element for 1 hour = 4.5 KwH of energy use. The current price of electricity in Austin ranges between 9.5 to13 cents per KwH depending on your provider and plan.

Solar Thermal - Solar meaning sun, thermal meaning heat, is any system that uses the sun's heat to provide energy. Since there is no conversion from one form of energy to another(ie photovoltaics turning photons into electrons), solar thermal is very efficient.

Thermal Efficiency - In water heating, this typically means the amount of energy delivered divided by the amount of energy used. A typical gas water heater is 50% to 60% thermally efficient, meaning almost half of the energy in the gas is lost through the vent. Most electric water heaters have a thermal efficiency of 90% or higher, since the heating element is directly immersed in the tank. However, this efficiency is offset normally by electricity being more expensive.

System Efficiency - Describes the cost of operating a solar water heater vs. operating a traditional water heater. If a solar water heater is 85% efficient, then its operating costs are 85% less than that of a normal water heater.

BTU - British Thermal Unit. Is the amount of energy required to heat 1 pound of water 1 degree Farenheit. Water weighs 8.3 pounds per gallon. Therefore, it takes about 21,000 BTUs to heat one 50 gallon water heater from 70 degrees to 120 degrees.

KwH to BTU - 3,413 BTU = 1 KwH

Standby loss- The energy lost through the tank walls of a water heater due to the surrounding air being cooler than the water in the tank. A typical water heater will lose 2 degrees per hour in standby loss. This equates, generally, to about $12 per month in additional heating costs. Tankless water heating marketers have done a great job convincing people that their product will cut heating expenses by 50% or more, but this is simply not the case. Most of the energy use by a water heater is to raise the temperature of the water. Tankless systems still use traditional fuels to achieve this, thus are inherently less efficient than solar heating.

Therm -1 therm of natural gas = about 100,000 BTU, 1 therm of propane = about 90,000 BTU. These high energy outputs are offset by the relative inefficiency of gas fired heating system.

CCF - 1 hundred cubic feet(usually gas). 1 CCF of gas = 1 therm(roughly)

Tempered Glass - is formed by unevenly heating and cooling layers of the glass during panel production. When the layers cool unevenly, they contract at different rates. This creates internal tension in the glass, making it much stronger. Tempered glass in our panels has been rated for up to golf ball sized hail in testing.