Friday, August 31, 2012

Water heating is bigger than ever

A lot has changed in energy since the 70's, but we still use a lot of it.
We do have a bit of good news on the residential energy efficiency front.  The average American home uses just about the same amount of total energy as it did 30 years ago despite a rising standard of living and more plug-in creature comforts than ever before.  It's actually trending down on a per household basis.

I see two problems with this however.  First of all, we have a whole lot more homes today than in 1978.  We're around 115 million households today where we were only at 68 million in the 1970s.  While flat or even slightly declining per household energy consumption is great, 47 million new households means that we're using a lot more energy on the whole than ever before.

Where we use energy in our homes--1978 and today.
The second problem I see with this data is highlighted in the two pie charts above.  Where we use energy has shifted rather dramatically.  Due to key improvements in building technology and code, space heating accounts for much less of our homes' energy budget.  Air sealing, insulation, and mechanical system efficiency enhancements have worked.  This was low hanging fruit though and further total efficiency gains are going to be harder to achieve.

Take a look at the water heating portion of the chart.  20% of our residential energy goes to heating up water for showers, cooking, and cleaning.  This is a very predictable energy load that is completely unrelated to any other mechanical system in the house or to the quality of the building envelope.  As we look to make further cuts in per capita and total energy consumption, the water heating load is an excellent place to focus.
Germany has far less sun & far more solar than the US.  No one thinks the Germans are flaky environmental nuts either.
This is where solar water heating can make a big impact.  We have more than enough sun anywhere in the US to offset the water heating energy requirement with existing solar collector technologies commercially available today. Despite the cyclical ups and downs on the prices of specific types of energy, energy efficiency strategies enacted today will pay for themselves over the long run.

The answer to our energy problems rises every morning.