The people moving into a new home and their behavior can easily have a larger influence on energy consumption than items a builder may be able to control, according to research recently published by NAHB.
The NAHB research is based on the U.S. Energy Information Administration’s latest Residential Energy Consumption Survey data. A previous post showed how these data can be used to breakdown energy consumption by age of the home. This post discusses a statistical model developed by NAHB to estimate the amount of electricity used for something other than heating, ventilation or air conditioning (HVAC). Non-HVAC electricity is important, because it accounts for more than 70 percent of a home’s total energy use, and is not as obviously related to the characteristics of a home as the home’s size or its insulation.
The model can be used to define a baseline home with average characteristics that uses electricity for cooking and water heating and consumes about 28 million BTUs of electricity a year for something other than HVAC. The figure below shows how doubling the size of the home and adding or increasing the capacity of items usually provided by a builder (e.g., a water heater or ceiling fans) adds 5.5 million BTUs per year onto the baseline.
The largest individual effect comes from the extra large water heater. The pure effect of doubling the size is positive, but quite small. Of course, even if installed by a builder, choice of the item may be heavily influenced by local availability, code requirements, and customer preferences.
The next figure shows how items usually purchased separately by home owners without builder involvement can easily increase electricity use by more than this. The values were chosen to be above the typical baseline, but still within a range that occurs fairly often in practice. In total, these household-purchased items increase annual energy use by 11.9 million BTUs, about twice as much as the builder-installed features.
As the next figure shows, the impact of household characteristics and behavior can be even larger. Again, the numbers are above average but still generally in a realistic range. An aggressive assumption of doubling income is shown, primarily to show that the effect of income is relatively modest compared to some of the other items in the figure. In total, these household characteristic and behavior changes add more than 21 million BTUs onto the 28 million BTU baseline.