The Department of Housing and Urban Development (HUD) residential solar heating and cooling demonstration program provided funding support for over 600 solar projects. These projects provide the largest single data base of solar heating and cooling experience now available. These data suggest that maintenance and system operation have been mixed even though system configurations are similar throughout the program. HUD has been involved in the upgrading of one-third of the 600 solar projects and now can report that projects can be maintained with a more uniform level of effort.