The residential energy use pie

Residential energy use called out by function in a pie chart matters very much.  This is because such information can point us toward that next best goal to reduce consumption and save money.

Residential energy use by category

Not every home will consume the same proportions by function of the pie chart at left, but the variance will be least among the largest slices of this pie for the greatest consumption.  Taken together, space heating, cooling, and hot water account for 72% in this example.  Lighting, cooking, refrigeration and plug loads comprise the remainder.


The three functions totaling 72% are all thermal concentrations that are insulation dependent to minimize heat loss or gain.  This is why the three most important considerations in new construction or energy retrofits are “envelope, envelope, and envelope.”  Heeding this concern boosts the resistance of the home’s walls, ceilings, and floors to the movement of thermal energy, and the ability of the hot water heater to contain it before it is consumed.


Modern housing and occupied buildings have been fighting against envelope losses and gains due to tighter construction practices like those in California’s Title-24 Building Standards.  With better thermal protection from outside air temperature swings, heating and cooling equipment can be sized smaller.  This reduces both the capital cost of HVAC equipment and its operating costs as a portion of utility bills.  As I like to say, “Insulation doesn’t need any maintenance, it just saves you money every day after installation for the life of the building.”  Residential energy use can drop in any home with envelope retrofits.


Since geothermal heat pumps (GHPs) provide carbonless heating, cooling, and hot water for up to 72% of a residence’s major energy loads, you can see why this website boasts of their climate saving potential.  GHPs concentrate and move Btus with ease, and fit with the coming all-electric economy that itself will be generated by renewable means.  They are the most efficient HVAC equipment on the planet.

Bill Martin