This paper presents information on the design, construction, and operational experience of four residential solar space-heating systems located in the Washington, D.C., metropolitan area. These systems have been in operation for periods ranging from three to five heating seasons. Each installation is in a detached single-family residence. All of the systems were installed commercially with private funds and, except for applicable federal, state, and local tax benefits, have not received any government financing. Each of the systems is a unique design. The intent of the paper is to present the systems comparatively.

Units: Dual