Calculations Used in Energy Audits

Utility Bill Analysis

• A fundamental task of an audit is the review of the home's utility bills for a period of one to three years. Electricity and fuel rates and the home's energy usage are trended to show maximum and minimum energy loads during seasons, and to compare costs to typical homes in similar climates.

Air Leakage Analysis

• Another important set of calculations is the rate of air infiltration of the house through the building shell. This analysis shows how airtight the house is and identifies leaks and drafts. Windows; doors; cracks; and air gaps in walls, foundations and attics all contribute to air leakage. Audit recommendations should reveal the areas that would benefit from air sealing, as well as the estimated financial and energy savings.

Thermal Analysis

• An audit also reviews the insulation levels of a home and how effectively it retains heated air in the winter or cool air in the summer. The auditor examines the Insulation levels in the attic, roof, basement, foundation, walls and unconditioned spaces and makes recommendations on how much and where to add more. The cost of the measure, estimated savings and the payback period are calculated and presented in the report.

Mechanical Systems Analysis

• An audit examines the mechanical system's age, efficiencies and overall condition. The home's mechanicals consist of heating, cooling and hot water systems, circulation systems and air duct systems. If opportunities exist for renewable energy such as solar heating, electricity or hot water, they would be presented and analyzed along with a cost and savings comparison for replacement with high-efficiency models.

Appliance Performance Analysis

• Audits usually include an analysis of the home's electrical appliances including lighting, refrigerators, air conditioners, electronics, washer/dryer and the like. The report details a calculation of replacement costs for older appliances, based on the annual hours of usage, their operating costs and energy savings. The report might also make recommendations on load management by modifying the usage and scheduling of various appliances.