Columnists: Alan Meier, LBNL

Published on: 4 Oct 2011

The bumpy road to net-zero energy

It’s easy to lose the longer perspective when we are involved in the day-to-day efforts to save energy.  That’s why I want to focus on a single home—Danny Parker’s home in Florida, USA—to illustrate the bumpy road to zero-energy use. The chart shows monthly electricity use for twenty-one years, along with many of the major events in his household. (Follow the green line to see the consumption smoothed of its summer air conditioning spikes.)

Click the image to download a larger version.


When the Parkers moved into the house in 1989, Mr. Parker and his wife used roughly 10,000 kWh/year. This was already considerably less energy than the average in his region and, by coincidence, it’s also the US average residential electricity use. Over the next 20 years, Mr. Parker 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 his incandescent lights with CFLs.

There were other events affecting energy use. The babies arrived: first Sarah, then Wade. In 1998, they added 50 m 2 of floor area. In 2005 the children–no longer babies–convinced their parents to buy a DVR and flat screen. In 2006, Mr. Parker bought an energy feedback device though it wasn’t clear if anybody besides him understood it. Finally, in 2009, the Parkers installed a 5 kW PV system. Meanwhile, appliances were being replaced again. In 2010, the Parkers replaced the refrigerator again. The “new” air conditioner was replaced in 2010.

Over those twenty-one years, the Parker’s 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 Parker’s house is exporting electricity. This house was in no way special and yet through choice of appliance, equipment and components, it was able to reach zero energy through using both efficiency and renewable energy. Arguably, many millions of households around the world could achieve a similar outcome, taking into account different cultural and climatic differences.

This chart tells us much more. A lengthy report would be needed to explore all of the features and implications but here are some. The policy implications are in italics.

  1. The progress of the Parker household towards net zero electricity consumption is bumpy. More puzzling, the fluctuations in energy use don’t seem to correspond to the installation of the conservation measures (or at least not always). Policymakers will need better evaluation tools to monitor progress towards their goals.
  2. Many conservation measures are required to significantly reduce electricity use. Policymakers must think comprehensively about efficiency.
  3. 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. (On the other hand, per-capita electricity use fell 50%.) Policymakers need to make allowances for the good bumps.
  4. Homes can grow in size. This one increased roughly 25% in floor area. Nevertheless, we don’t see much increase in electricity use. That’s because Mr. Parker was careful in the design and construction of the addition. Policymakers need to target renovations as well as new construction.
  5. Major appliances, such as the refrigerator, needed to be replaced twice during the 20-year period. This means that policymakers may get two opportunities to improve the efficiency of the appliance stock on the path towards zero net energy. We must also expect to visit each home many times.
  6. In summers, electricity consumption still exceeds available supply; thus we will need to take into account peak consumption as well as average.

Europeans may have difficulty imagining the transformation that must occur in order to achieve the emissions targets by 2030 (and beyond), but the Parker household gives a realistic portrait of the steps–both forwards and backwards–that could make it happen. Surely if the Parker household in Florida can achieve this, then so can the households of Monsieur Dupont, Señora Gomez, and Herr Schmidt in Europe.

Of course we can argue that this home is not a fair example and that we ignored the energy use of their cars, and the new households soon to be created by Danny’s children Sarah and Wade. These are all valid objections but they don’t detract from the larger 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.

The views expressed in this column are those of the columnist and do not necessarily reflect the views of eceee or any of its members.

Other columns by Alan Meier