The Department of Energy (DOE) has established an extensive Building Energy Tools directory on the web. This directory includes over 60 tools from research grade software to commercial products with thousands of users. The common thread for all the software is improving energy efficiency or incorporating renewable energy concepts in buildings.

There are several software programs highlighted below. These programs are designed to calculate energy savings in homes are highlighted. Many of the programs listed below are complex in nature, and may require the assistance of a technical expert. Additionally, DOE's directory includes additional software tools not highlighted here, but may be useful in calculating energy efficiency.

• The Building Life-Cycle Cost Program (BLCC) software evaluates the costs and benefits of energy and water conservation and renewable energy projects. This software computes and compares the lifecycle cost of two or more alternative designs to determine which has the lowest lifecycle cost, therefore is more economical in the end. BLCC5 and BLCC4 are the main programs in the set of six National Institute of Standards and Technology (NIST) computer programs that provide analysis of capital investments in buildings.
  
  
• The DISCOUNT software performs the individual discounting operations required in lifecycle cost analysis. DISCOUNT computes present values of future and periodic amounts, future values of present and periodic amounts, and annual-value equivalents of present and future amounts.
  
  
• The EMISS 1.00 is a special-purpose computer program for use in generating data files that can be imported into the BLCC programs. EMS generates a file of local air-pollution emission coefficients. The resulting data can be accessed by BLCC4 to calculate reductions in air pollution emissions attributable to energy conservation investments in building and building systems.
  
  
• The Electricity Rates (ERATES) software is used to calculate monthly and annual electric costs for a facility, building, or system under a wide range of electric utility rate schedules. Typically, these calculations can support Engineering-economic studies that assess the cost-effectiveness of energy conservation measures or measures to shift electricity use from on peak to off-peak times.
  
  
• DOE-2 / EnergyPlus is available free from the DOE Office of Building, Technology, State, and Community Programs. This software is an energy simulation program, designed for modeling buildings with associated heating, cooling, lighting, and other energy flows.
  
  
• Energy-10 helps architects and building designers quickly identify the most cost-effective, energy-saving measures for small commercial and residential buildings. ENERGY-10 can identify the best combination of energy-efficient strategies, including day lighting, passive solar heating, and high-efficiency mechanical systems. Using ENERGY-10 at a project's start takes less than an hour and can result in energy savings of 40%-70%, with little or no increase in construction costs.