November 9, 2015

As American homes get bigger, energy efficiency gains are wiped out

U.S. Homes More Energy-Efficient, But They Are Now Larger, TooU.S. homes have become considerably more energy-efficient over the past four decades, according to government data. But homes also are a lot bigger than they used to be, and their growing girth wipes out nearly all the efficiency gains.

According to preliminary figures from the Department of Energy’s Office of Energy Efficiency and Renewable Energy, the average U.S. home used 101,800 British thermal units (Btu) of energy per square foot in 2012, the most recent year with available data. That’s 31% less than in 1970, after adjusting for weather effects and efficiency improvements in electricity generation.

And while the total number of housing units rose by 80% over the past four decades, collectively they used just 45% more Btu than in 1970. (The government uses Btu – the amount of heat needed to raise a pound of water 1 degree Fahrenheit – as a single common measure for electricity, heating fuel and other forms of household energy.)

All of this is good news for energy conservation. After all, a new Pew Research Center survey found that two-thirds of Americans say people will have to make major changes in the way they live to reduce the effects of global climate change. And many such changes can be made right at home.

But like Americans’ waistlines, U.S. homes have been expanding steadily over the years: The average home in 2012 was estimated at 1,864 square feet, 28% bigger than in 1970.

While some homeowners do add onto their existing structures, the trend is driven largely by new construction. According to the Census Bureau, the average new single-family house completed last year was 2,657 square feet – 57% larger than four decades earlier. While the biggest new homes are being built in the South (an average of 2,711 square feet last year), home sizes have grown the most in the Northeast: a 64% increase in average new-home size over the past four decades.

Today’s New Homes 60% Larger Than in 1973

What all of this means is that, after dropping sharply during the 1970s, the overall energy intensity of U.S. homes has changed little over the past three decades. Energy intensity is a metric that compares the amount of energy used against some unit of economic activity – households, in the case of the residential sector.

The average home used 183 million Btu in 1981 and 188.7 million in 2011; energy intensity did fall in 2012, to a preliminary read of 174.7 million Btu, but that was mainly due to weather. (Other factors, including geographic population shifts and changes in housing type, have had relatively little impact on overall energy intensity.) Think of someone scarfing down a chili cheeseburger and fries after an hour on the elliptical, and then wondering why he never seems to lose weight.

What has changed, though, is how households use energy. According to the Energy Department’s quadrennial Residential Energy Consumption Survey, in 1993 more than half (53.1%) of total household energy consumption went to heating living spaces, versus 41.5% in 2009 (those are the earliest and latest years, respectively, for which comparable data are available). Conversely, the share of energy consumption that goes to appliances, electronics and lighting rose from 24% to 34.6% over that same period. (The energy shares for water heating and air conditioning didn’t change much.)

Topics: Energy and Environment, Lifestyle

  1. Photo of Drew DeSilver

    is a senior writer at Pew Research Center.

5 Comments

  1. Don Macdonald7 months ago

    Veritatis Advisors has found in its case study results implementing energy efficiency projects and behavioral change management that Human Behavior predicates additional consumption until the cost of that consumption becomes too great. This should not be a surprise to anyone.

    As the number of cars, houses, buildings, devices, and systems grow more energy efficient there is a false belief we can consume more impacting less. This too is false. This is exactly why utility efficiency programs fail to curb behavioral energy consumption. Humans need to have the “efficiency” decision taken out of the equation for them, built into the products software logic (aka Nest Thermostats), fuel efficiency devices in cars (well except for VW), in building lighting sensors, CO2 monitors, boiler systems and so forth. This relinquishing of “efficiency choice” will not come easy until the metrics for E,M&V are well understood, non-utility based, and non-political.

    The belief these more efficient products and systems reduce net consumption is incorrect. Humans, even well intending “Green” ones will consume more.

  2. Paulo8 months ago

    Like more efficient automobile motor leads to bigger motors and/or more travels.

    It’s just human nature at work!

  3. Sam Borgeson8 months ago

    I studied building science and worked with this type of data on a regular basis. I think you should be more careful with your interpretation.

    If you look at the figures you can see that the average home size trend has been in effect for a long time, but the real news is that home sizes haven’t been growing much lately. This is very likely due to the recession (and the uneven distribution of wealth in the recovery), but also to the demographic trend of urbanization.

    In addition, we should be careful in our interpretation of energy consumption normalized by square footage. If we agree that people direct energy use, you would expect some uses (i.e. appliances, entertainment, water heating etc.) to remain roughly constant for the same family in a bigger house, while others (i.e. heating, cooling, possibly lighting) to scale with the home size. What this means is that larger homes can CAUSE decreased energy intensity as the fixed loads are spread across more space. So when we say that per sqft efficiency gains are offset by growing homes, we might have the causality reversed! It would be useful to also report on un-normalized end-use averages and possibly per-capita end-use averages as well.

    1. Mel8 months ago

      You lost me at, “What this means is that larger homes can CAUSE decreased energy intensity as the fixed loads are spread across more space.”

      More space implies more needed heat/ac, a larger or multiple water heaters, more rooms with more lights, tv’s, appliances. Depending on the heating system – more natural gas or more oil to run electrical appliances to run the hvac. How you can say more space needs less energy doesn’t sound right at all.

      1. Mark7 months ago

        One reason energy intensity decreases in larger homes is that while there are more lights, appliances, etc. these do not increase at the same rate as the size of the house. For example, if you compare two homes, a 2500 sqft house and a 1800 sqft house, they probably both have 1 refrigerator, 1 dishwasher, 1 clothes washer, 1 clothes dryer, etc. – so in the bigger house the energy consumption is spread across more square feet, resulting in less energy per square foot even though its more energy overall.