Mississauga: 50,000 streetlights, a meter in every node

Mississauga owned about 50,000 streetlights on residential, collector and arterial roads. In 2011 they cost the City $6.1 million a year in electricity and $2.3 million a year in maintenance; both lines were the target.

The City approved a $26 million conversion, debt-financed, with $1.4 million in incentive eligibility. Work ran from November 2012 to December 2015. Entrusted to Dimonoff in 2012, it was the first large-scale smart city project in Canada.

Converting the fixtures to LED was the easy part. The real question was how to prove actual consumption once the lights no longer drew a fixed, assumed load.

Every converted light received a networked node. The nodes form a wireless mesh; each network area of about 300 nodes reports through a central gateway to the Dimonoff | SCMS platform, where groups, schedules and dimming profiles are defined.

The distinguishing element sits inside the node: each one contains a built-in electrical meter. The City worked with Enersource, its local utility, to have those meters accepted as revenue meters. It installed a full-scale adaptive controls system with its LED conversion in 2014 and developed, with the utility, a method for demonstrating the metering integrity of the controls.

The City reports a 55% reduction in energy costs against the 2011 baseline. Maintenance costs fell as well; the City describes that reduction as significant without publishing a figure.

Because the meter is in the node, the saving is measured rather than modelled. Under an unmetered street lighting tariff, the utility bills an assumed load per fixture that dimming does not change, so the energy saved never reaches the invoice. Revenue metering in every node closes that gap.