recent study comparing projected and actual electricity used in homes constructed to meet Washington’s green certification standard – Built Green – revealed that certified homes used up to 40% less electricity than non-certified homes, in some cases making Built Green homes twice as efficient as predicted.

The largest study of its kind to examine actual savings from green home-building certification programs, researchers analyzed data provided by electric utility Seattle City Light, comparing their modeled expectations with their actual electricity use from a year of occupancy. The study showed that certified homes saved homeowners more than $500 per year in electricity bills, and prevented more than a half ton of carbon emissions per home.

Built Green is the residential green building certification program of the Master Builders Association of King and Snohomish Counties. The Master Builders Association is the largest local homebuilding association in the country and it founded Built Green in 1999. Since then, Built Green has certified over 31,000 units.

“These electricity savings prove that builders, local governments and utilities can effectively partner to reduce carbon emissions in their communities,” said Erich Armbruster, president of Ashworth Homes and 2018 Board President of the Master Builders Association of King and Snohomish Counties. “Residents are looking for green homes which are more comfortable and protect our Northwest environment; 52 percent of homes built in Seattle earned Built Green certification in 2016.”

The study was led by Leah Missik, Built Green Program Manager, in conjunction with Seattle’s Department of Construction and Inspections and Seattle City Light. Review of the study was conducted by the environmental consulting firm Rushing. The study is unique because researchers had access to large-scale residential electricity use data provided by the electric utility, Seattle City Light. Built Green obtained data for all single-family and townhomes built in Seattle in 2014 and analyzed 746 of the homes, comparing their modeled expectations with their actual electricity use.

“The yearly savings for the average Built Green home are equivalent to the electricity it would take to power a 12W LED light bulb continuously for more than 44 years, or offset the energy production of more than 13 solar panels,” said Missik. “The savings can translate into greater purchasing power for buyers, allowing them to consider homes with a more expensive up-front cost, knowing they’ll cost less to operate in the long run.”

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