Our Environmental Impact Rating for the Heating Technology Category is based on the technology's average annual emissions of CO2. Annual CO2 emissions are calculated according to the average emissions associated with the production of each energy source (e.g. electricity, natural gas, etc.) and the average amount of energy consumed per year for each technology.

The higher the Environmental Impact Rating, the less-emitting the technology is of CO2 emissions due to its energy source (higher rated technologies burn cleaner fuel) and efficiency.

Our Consumption Rating for the Heating Technology Category is based on average annual kilowatt hours consumed for each technology. The higher the Consumption Rating, the less energy-consuming and more efficient the technology.

Our Lifecycle Cost Rating for the Heating Technology Category is based on the technology's average annual cost of operation (energy expenses) over an 18-year period plus its average purchase price, including installation and 2009 Federal tax credits. The higher the Lifecycle Cost Rating, the more cost-effective the technology.

Our Price Rating for the Cooling Technology Category is based on average purchase and installation prices for each technology, including the 2009 Federal tax credit, if applicable. These prices are rough estimates; contact your local HVAC contractor for accurate prices.

The higher the Price Rating, the lower the price of the technology.