Greenhouse Gas Savings from Use of City-Owned EV Charging Stations

Charging stations were installed starting in January 2012: there is now one dual (240volt) unit at the Community Center, two dual units and one single unit at City Hall. Other locations around Mercer Island also offer EV charging, such as many of the MI School District campuses, the Boys and Girls Club, as well as various private businesses. The Island's only fast-charge (480volt) units are located in Town Center at the New Seasons Market. The 2015 decline in City charger usage corresponded with the end of free charging and the imposition of a small hourly fee. This chart displays emissions savings from City-owned EV charging stations at City Hall and Community Center, vs. traditional combustion-engine vehicles. Electric vehicles produce no direct emissions to the air and less pollution into waterways than gasoline combustion engines; indirect emissions (i.e. from power plants) are also lower due to the region’s cleaner power portfolio mix.

Increasing Electric Vehicle Ownership

Statewide, total EV ownership has risen dramatically over the past 3 years, jumping from approximately 9,700 in 2014 to 25,000 in 2017 (data gathered in June yearly by WSDOT) -- this includes both Battery Electric Vehicles and Plug-in Hybrid EVs. On Mercer Island, the increases have been similar, as depicted in the graphs to the right.

Fuel Use by City Vehicles

The bar graph depicts total fuel use (diesel, gasoline, propane) by all of the City's vehicle fleet over the past 5 years. The pie chart depicts fuel use by engine type: currently, about 25% of the City's fleet emissions come from diesel vehicles, and 75% from gasoline vehicles. The City owns several propane vehicles (mostly mowers) and 6 electric vehicles (3 off-road UTV's for parks maintenance, and 3 on-road passenger cars for field staff) [Note: Due to limited data availability, data prior to 2016 are less informative about fuel type -- we are working on gathering deeper data over the coming months].

What Vehicle Type Is the Biggest Contributor to Emissions?

In Mercer Island, like most other Eastside communities, travel by passenger vehicle is by far the largest contributor to vehicle-related greenhouse gas emissions. Vehicle Miles Traveled (VMT) is a sum of all trips in a year that start or end on Mercer Island, as well as trips that drive-through on Interstate-90 -- this is extrapolated from regional data (from Puget Sound Regional Council's 4k model) and then converted to CO2 emissions.