The Northwest Energy Efficiency Alliance (NEEA) contracted with Energy 350 and ILLUME Advising, LLC to conduct field testing to demonstrate performance of combi systems in cold northwest climates and identify potential barriers to market adoption. According to results from this field study, combi systems, also known as combination water and space heating systems, save more energy compared to conventional systems in cold northwest climates. The field study included sites in western and central Oregon and eastern Washington.
The field trial focused on combi technologies that use condensing tankless water heaters to provide space heating via a hydronic coil and domestic hot water on demand. The study showed that on average, these combi systems saved 24% more therms annually relative to a conventional forced-air furnace with an 80% Annual Fuel Utilization Efficiency (AFUE) and a tank water heater with a 0.62 Uniform Energy Factor (UEF). In addition, participant experience surveys revealed high rates of satisfaction with their combi units over the course of the year-long field trial.