Bayview Tower

Seattle, Washington

Pioneering Heat Pump Water Heating for Affordable Housing

Located in Seattle’s downtown Belltown neighborhood, this 13-story, 100-unit multifamily building offers affordable public housing to the elderly and disabled. Bayview Tower apartments is the first project to use the Mitsubishi QAHV (HEAT2O) heat pump water heater in the United States. When engineers planned this system, they worked with Steffes to design a skid-mounted package that included the heat pump, primary hot water storage and control system. The HEAT2O uses CO2 as a refrigerant—a great candidate for outdoor installations in cooler climates. The value of the skid is that all equipment is plumbed, housed, and ready for hook-up on site. The replacement of the water heating system was accomplished without disrupting water service to the residents for more than a few hours! This project was also the first demonstration of the ability to shift the operation of the system off peak utility demand periods to dramatically reduce peak electric loads at the building.

Key highlights of this project are:

• Hot water has been delivered reliably by the system for over a year. There has been one instance where a pump failure caused the backup system to operate.
• Annual SystemCOP of ~2.3 (inclusive of temperature maintenance).
• Opportunity to improve HX package to increase SystemCOP to ~3.2.
• Successful installation of packaged system.
• Proven exceptional/consistent load shift system.

Learn more about this project here:

• Pilot project in Seattle shows central heat pump water heaters can act as massive hot water batteries that help reduce carbon emissions. New Buildings Institute, February 2023.
• Mitsubishi Heat2O Hot Water Load Shift Demonstration and Simulation Analysis: at Bayview Towers, Seattle, WA. Bonneville Power Administration, June 2023.
• Demonstration and M&V: Commercial Heat Pump Water Heating System using the Mitsubishi HEAT2O in Origin by Steffes Plug-and-Play Package at Bayview Tower, Seattle WA. Bonneville Power Administration, March 2022.