Excitement over solar thermal built throughout the late 1970s , reaching its peak in 1984 when 17.2 million square feet of solar collectors were manufactured. After that, the Energy Information Administration explained back in 1996, things went south.

From 1984 to 1986, the number of manufacturing firms in the solar industry declined by 127 [109], probably due to the expiration of the 40-percent residential and 15-percent business energy tax credits. The decline in industrial companies intensified with the drop in oil prices in 1986. The reinstatement of the business energy tax credit at the 15-percent level for 1986, at the 12-percent level for 1987 through 1991, and at the 10-percent level in 1992 and increasing oil prices after 1986 appear to have had little effect on drawing investors and companies into manufacturing solar thermal collectors. Since 1990, the rate of growth of solar collector shipments has stabilized at about 4 percent per year.”

That makes the data for what happened after the crash interesting. Here are the post-crash numbers: