On January 28, 2015 the District of Columbia published the second year of energy benchmarking data collected from private buildings. This year’s public disclosure applies to all commercial buildings 100,000 sf and larger while last year’s public disclosure was for all buildings 150,000 sf or bigger. Data published are drawn from the EPA’s ENERGY STAR Portfolio Manager and include building details such as gsf and principal building activity along with annual consumption for major fuels (electric, natural gas, steam), water, and calculated green house gas emission (associated with fuels). Also published are annual site EUI (energy use intensity) and weather-normalized source EUI metrics, commonly used to asses building energy use.
The District Department of the Environment has analyzed these two years of data and concluded the following:
- DC commercial buildings continue to be exceptionally efficient. The median reported ENERGY STAR® score for private commercial buildings in the District was 74 out of 100—well above the national median score of 50.
- Buildings increased in efficiency from 2012 to 2013. Also, overall site energy use went up by 1.5% among buildings that reported 2012 and 2013 data. However, when accounting for weather impacts and fuel differences, the weather-normalized source energy use for the same set of buildings decreased by 3% in 2013.
These claims are simply unjustified.
In particular consider the second point — that 2013 source energy used by DC buildings is 3% lower than it was in 2012 — demonstrating improved energy efficiency. This claim is based on weather-normalized source energy numbers produced by the EPA’s Portfolio Manager. The problem is that the EPA lowered its site-to-source energy conversion factor for electricity from 3.34 to 3.14 in July 2013 — a 6% reduction. Because of this simple change, any building that has exactly the same energy purchases for 2013 that it did in 2012 will, according to Portfolio Manager, be using 4-6% less source energy in 2013 (depending on the amount of non-electric energy use). In other words — the District finds its buildings used 3% less source energy in 2013 than in 2012 when, in fact, by doing nothing, all US buildings saved 5-6% in source energy over this same time frame.
It is said that “a rising tide lifts all boats.” In this case the Washington DC boat did not rise quite as much as other boats.
More seriously, such small differences (1% – 3%) in average site or source energy are not resolvable within the statistical uncertainty of these numbers. The standard deviations of the 2012 and 2013 mean site and source EUI for DC buildings are too large to rule out the possibility that such small changes are simply accidental, rather than reflective of any trend. Scientists would know that. Politicians would not — nor would they care if it makes or a good sound bite.
Let me now address the other claim. It may well be true that the median ENERGY STAR score for district buildings is 74. I cannot confirm this – but I have no reason to doubt its veracity. But there are no data to support the assumption that the median ENERGY STAR score for all commecial buildings is 50. All evidence suggests that the national median score is substantially higher — in the 60-70 range, depending on the building type. My recent analysis shows that the science that underpins these ENERGY STAR scores is wanting. ENERGY STAR scores have little or no quantiative value and certainly DO NOT indicate a building’s energy efficiency ranking with respect to its national peer group — despite the EPA’s claims to the contrary.
The claim that the median score for US buildings is 50 is similar to making the claim that the median college course grade is a “C.” Imagine your daughter comes home from College and says, “my GPA is 2.8 (C+) which is significantly higher than the (presumed) median grade of 2.0 (C). You should be very proud of my performance.” The problem is the actual median college grade is much closer to 3.3 (B+). Its called grade inflation. Its gone on for so many years that we all know the median grade is not a “C.” Until recently ENERGY STAR scores were mostly secret — so the score inflation was not so apparent. But the publication of ENERGY STAR scores for large numbers of buildings as a result of laws such as those passed in Washington DC has removed the cloak — and the inflation is no longer hidden.
ENERGY STAR scores are no more than a “score” in a rating game whose ad hoc rules are set by the EPA in consultation with constituency groups. It seems to have motivational value, and there is nothing wrong with building owners voluntarily agreeing to play this game. But like fantasy football, it is not to be confused with the real game.