Here in Chicago, we find many 3-4 story residential buildings that get divided into as many as 12 units. Some of these buildings are owned as condos with separate unit owners and some have a single owner managing the units as apartments. In either case, domestic water heating in this style of building can either be done with a central boiler (very common) or with individual water heaters for each unit (less common). Plumbing a solar water heater as a retrofit to a multifamily building with individual water heaters is probably a less ideal application so I'll highlight two ways to work with a central boiler.
|The Chicago Graystone--a typical residential building in the city|
Case 1: Condo
In a condominium, each unit is individually owned. The unit owner pays a mortgage on their unit as well as an association assessment to handle shared expenses (snow removal, common area heating/cooling/lighting, landscaping, roof repair, etc). In the case of a condo building with a central water heater, domestic water heating is a shared expense. In this case, a modestly sized solar water heater could be plumbed in-line before the existing water heater to pre-heat all incoming cold water into that tank. A 6-unit building could see 60-80% water heating cost reduction with just a 3-4 panel system. The cost of this system would be shared by the unit owners. The unit owners would then calculate their ownership percentage of the new solar system installation costs to claim the 30% federal tax credit as well as any state or local incentives that might apply. As a rule of thumb, 1 solar collector for every 2 units should meet federal tax incentive requirements for system productivity. While organizing a condo association around a capital improvement project like this may be akin to herding cats, implementation of a solar water heater could be very simple to do with a solid return on investment for the association.
|Cat Herding--much like many condo meetings I've been to|
Case 2: Apartment Building
Many landlords of buildings with central boilers for water heating provide their tenants with hot water as part of the monthly rent. This scenario may be one of the most attractive applications for a solar water heating system. Like in a condo building with a central boiler, a solar water heater would pre-heat water flowing into an existing water heater. The benefits to the landlord are very attractive. Not only will he or she reduce their monthly costs on water heating bills, but the solar system will bring them a 30% federal tax credit, accelerated depreciation benefit, any state/local incentives, and position the apartment as one that is more attractive to younger tenants than comparable other buildings without solar. On top of all that, the building will actually have more hot water to draw on so the building manager will get fewer complaints for cold showers.
|Solar may have kept him out of hot water with his tenants|
For further reading, Wisconsin's Focus on Energy program has developed a fact sheet detailing many of the advantages of solar water heating in multifamily applications. I recommend that you check it out.