Perhaps the greatest challenge to promoting energy efficiency is that you can’t see it. People understand electricity produced from a PV collector on the roof, and a kWh meter can easily report precisely how much energy was generated. But with more-efficient products, savings cannot be directly measured; instead, one must reckon the difference between a real and a hypothetical situation. This complexity creates a lingering uncertainty whether the promised savings did or did not actually occur.
There’s another paradox related to the evaluation of energy savings. Conscientious program managers and energy professionals should want to collect energy consumption data and perform the necessary analysis to be sure that the technology worked as expected. After all, how can one learn from mistakes if the mistakes aren’t observed? But the world works differently. If the preliminary estimates are proven correct, then program managers are open to criticism for wasting money on needless and expensive evaluations.
Alternatively, if the savings are less than expected, the managers are criticized for running ineffective programs or installing defective technologies. In an era of declining funding and short time horizons, they can’t win. I can understand why they would want to skip the measurements and I can sympathize with them.
That's why two articles in Home Energy's current issue quantifying energy and water savings from high-efficiency equipment are especially welcome. One article describes the energy and water savings to be gained from replacing old clothes washers with more-efficient units (see "Do Savings Come Out in the Wash?"). The savings are large: The most efficient units cut water and energy use almost 50% compared to the original units. And this study took place in mild San Diego; the savings could be greater in colder climates. The results also demonstrate the need to study the clothes washer, water heater, and clothes dryer in combination. The energy consumption of these three appliances is inextricably connected, depending as it does on hot- and cold-water consumption, internal water heating, and spin speed.
This study had another intriguing result: With increasingly efficient clothes washers, the energy conservation battlefields are shifting. The dryer is now the largest electricity consumer in many homes, thanks to shrinking consumption by refrigerators and lights. It’s time to develop and commercialize technologies that increase the efficiency of clothes dryers. Heat pump dryers are now crossing the Atlantic, but other technologies, such as heat recovery, deserve attention. A zero energy technology crossing both the Atlantic and the Pacific is line drying. It’s done overseas because energy is expensive, and some simple devices make it more convenient. A second battlefield may be the rising cost of detergents. Is Proctor and Gamble capturing an unfair share of the energy savings? This will be the topic of a future article.
The article on water savings found that replacement of relatively new toilets with better-designed, water-efficient units cut water use by greater than one third (see "Does Replacing Toilet Fixtures Save Water?"). Service calls fell dramatically, too. These outcomes demonstrate that the evaluator’s paradox has a third outcome, that is, the savings are larger than expected and include benefits not initially considered. A solid example was provided in this article with evidence that was obtained through only modest data collection and evaluation. Where skeptics question the difference between hypothetical and actual savings, these two articles prove that not only can efficiency gains be measured, but that the outcomes are real and substantial.
- Alan Meier