Reducing Carbon Footprint by replacing streetlights.

Earlier in 2014, the Municipal Properties office released this report on streetlight replacements.

The two projects described there reduce annual energy use by 218,769 kWh and 15,246 kWh respectively, for a total annual reduction of 234,015 kWh. (kWh = kilowatt-hours, the same unit of measurement as used on residential  electric bills). The document described these as  “reducing our carbon footprint” but by how much?

As a rough estimate, we can use the EPA estimated conversion factor. A more detailed conversion factor would depend on what mix of fuel is used by the generating equipment in the region during 2014.

The EPA gives this conversion factor: 6.89551 × 10-4 metric tons CO2 / kWh (from:

So:  234,015 kWh × 6.89551 × 10-4 metric tons CO2 / kWh  = 161 metric tons (throwing away everything to the right of the decimal point due to the spurious accuracy of the conversion factor).

Using the same EPA factor page, that’s the equivalent of taking 161/4.75 = taking 33 cars off the road, forever.   Or, based on NStar reports from 2009 of Acton residential electricity use, that’s the entire electric bill for 28 average-sized Acton homes.

A nice step forward. A long way to go.

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