The Home Energy Saver was the first Internet-based tool for calculating energy use in residential buildings. The approach taken by the web site is to provide users with results based on a minimum of user input, and then allowing progressively greater degrees of control in specifying the house and detailing energy consuming appliances characteristics, leading to more refined energy use calculations and more relevant upgrade recommendations. This approach allows users with limited knowledge or time to quickly access results that are generally applicable to their situation, while more informed or persistent users can get greater accuracy and relevance by customizing their house description. This design philosophy results in a progressive three-tiered approach to estimating energy consumption.

On the site entry page users are asked solely for their zip code and energy use estimates, upgrade recommendations and potential savings for the home can be calculated with no further inputs. These results are based on typical equipment for the housing stock in their region, largely based on the 2005 Residential Energy Consumption Survey (RECS) (US DOE. 2009), as described on the defaults page in this site.

After leaving the entry page the questions for the second, “simple inputs” level of the Home Energy Saver are displayed. This set of questions focuses on those appliances and housing characteristics that cause large variance in energy consumption (e.g. floor area, heating equipment, etc.). These key inputs can be used to refine the energy estimation beyond the generalized regional defaults.

Users can either calculate the energy used by their house based on the description provided by the “simple level” of questions or further refine the house description before calculating by accessing the third, “detailed inputs” level of the model. In the detailed input pages, they can adjust nearly all of the envelope, site and appliance characteristics that go into estimating energy consumption for their home.

When the user is satisfied with the house description, the calculate the energy consumption, which replaces the prior default results based on a house in their area. At this time they can also view more detailed reports.

For both the “simple inputs” and “detailed inputs” levels, the models used to estimate energy consumption are identical, with user-entered values substituting for default values as the user progresses through the “detailed inputs” level. There are six major categories (end-uses) where energy consumption is estimated; heating, cooling, water heating, major appliances, lighting, and miscellaneous equipment. The Home Energy Saver uses engineering models to estimate energy consumption for all these end-uses.