Over the last few years we've heard a lot about how if just invested in efficiency, like retrofitting old homes, we would save huge amounts of energy and massively reduce our emissions (not to mention create millions of jobs, reduce inner-city poverty, stimulate the economy, etc.). This was the subject of an op-ed in the New York Times on Monday.
But today, the Times ran an interesting correction on the op-ed page:
An Op-Ed article on Monday, about renovating older houses to save energy, included an incorrect figure for the number of homes that would need to be retrofitted every year to save 200 million barrels of oil over a decade. The figure is 300,000, not 3,000.
I went and looked up some of these numbers. According to the U.S. Energy Information Administration, Americans consumed over 20 million barrels of petroleum per day in 2007. About half of that petroleum is in the form of gasoline and the rest is heating oil, industrial distillates, kerosene, jet fuel, etc.
Few houses, of course, are heated by petroleum, so the comparison is inexact. Moreover, I doubt the assumptions embedded recognize that people tend to use more electricity when efficiency lowers the total monthly bill.
The numbers provided by the Times offer a sobering view of how little retrofits will actually do. Here's what we find: If we were to retrofit 3 million homes over the next decade, we would only consume 10 days less petroleum (.27% less). If we were to retrofit 10 times as many homes, 30 million, (which is almost certainly not possible to do in 10 years), we would save just 100 days of oil over a 10 year period (2.7% less).
If these numbers are basically right, then it's safe to conclude that building retrofits will not contribute significantly to reducing overall global emissions. They might be good for other reasons, but they are hardly the basis for a strategy to mitigate warming.
Those numbers look pretty much dead-on. The U.S. Residential sector consumed 20.77 Quadrillion BTUs (Quads) of primary energy in 2006 (from EIA's Annual Energy Outlook 2009). That's about 1/5th of total US energy consumption (which is at right about 100 Quads in 2006).
If we cumulatively retrofitted 1/3rd of all US homes to save 1/3rd of their energy, we'd save 20.77*.33*.33 = 2.26 Quads of energy annually. That's the energy equivalent of 373 million barrels of oil each year, or about 18 and a half days of oil consumption each year, 186 days over 10 years. That's also just 5% of annual oil consumption and about 2.25% of total US primary energy consumption.
So that puts the numbers Michael estimates above in the right ballpark. If 30 million homes is about 1/3rd of all US homes and they get about a 15-30% energy savings when retrofit (who knows how much the Times assumes you save when a home is retrofitted), you'd save on the order of 90-180 days worth of oil consumption equivalent, or just a couple percent of total U.S. energy demand for all of that effort. Helping save customers money on their energy bills is great, and there are plenty of reasons to want to do that, but we're not going to get to a sustainable and prosperous 21st century energy economy by retrofitting homes. It's just not the cornerstone of a smart energy policy.
Posted by: Jesse Jenkins at April 11, 2009 12:21 AM