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Editorial: The Bumpy Road to Net Zero Energy

July 01, 2011
July/August 2011
This article originally appeared in the July/August 2011 issue of Home Energy Magazine.
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It’s easy to lose the longer perspective when we are involved in day-to-day efforts to save energy. That’s why I want to focus on a single home—Danny Parker’s house in Florida—to illustrate the bumpy road to zero energy use. The figure on the right shows 21 years of electricity use, along with many of the major events in Danny’s household. (Follow the green line.)

When the Parkers moved into the house in 1989, Danny and his wife used roughly 10,000 kWh per year. (By coincidence, that’s also the national average residential electricity use.) Over the next 20 years, Danny installed many conservation measures and improvements. He added insulation, sealed ducts, installed a whole-house fan, replaced the refrigerator and air conditioner, and installed a PV-powered pump for the swimming pool. He also replaced all the incandescent lights with CFLs.
 

There were other events affecting energy use. The babies arrived— first Sarah, then Wade. In 1998, the Parkers added 500 square feet of floor area. In 2005, the children—no longer babies—convinced their parents to buy a digital video recorder (DVR) and a flat-screen TV. In 2006, Danny bought an energy feedback device, though it wasn’t clear if anybody besides him understood it. Finally, in 2009, the Parkers installed a 5kW PV system. Meanwhile, appliances were being replaced again. In 2010, the Parkers replaced the “new” refrigerator. The “new” air conditioner was replaced in 2010.

Over those 21 years, the Parkers’ energy use fell about 50% through efficiency improvements. They then eliminated the remaining 50% of grid-supplied power by installing a PV array. Now, in 2011, the Parkers’ house is exporting electricity.

The Parkers’ house was in no way special, yet it was able to reach net zero electricity use through a combination of familiar efficiency measures and investments in renewable energy. Arguably, many millions of households around the country could achieve similar results.

This rare perspective of 21 years of energy use reminds us that we shouldn’t treat a house as a static object. We can see that the progress of the Parker household toward net zero electricity consumption is hardly smooth, and many of the bumps don’t seem to correspond to particular technological events. Some of the bumps are good: The birth of two kids seemed to raise electricity use. That’s not really a surprise, but we shouldn’t forget this connection. The physical size of homes grows, too; this house increased roughly 25%. Nevertheless, we don’t see much increase in electricity use. Perhaps that’s because Danny was careful in the design and construction of the addition. Major appliances, such as the refrigerator and air conditioner, were replaced twice over the two decades. This is a reminder that efficiency experts should expect to visit each home several times in the path to net zero energy.

Of course one can argue that the Parkers’ home is not a fair example for comparison to an average home, and that we ignored natural-gas energy use. These are valid objections, but I don’t think they detract from the basic conclusion that a combination of vigorous conservation measures and appropriate use of renewable sources can achieve some—if not all—of our climate mitigation goals.

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