A method for generating a home energy efficiency label based on real-time measurements of gas-energy usage of a household and outside temperature data. The home energy efficiency label is calculated by correlating energy usage of the household to the outside temperature and presented to a home owner in real-time on a computer screen, thereby enabling prediction of potential energy savings by lowering indoor climate temperatures. The home energy efficiency label certifies home energy efficiency and can be used on a housing market including home appraising and financing.