‘Tax credits have been essential to the economic viability of wind farms so far, but will not be needed within a few years.” So said Christopher Flavin, now president emeritus of the Worldwatch Institute—in 1984.

Thirty years and billions of dollars later, the wind industry is still saying it needs taxpayer support. Congress is currently hearing this argument as it debates whether to extend the 22-year-old “production tax credit” in the lame-duck session. The PTC, which gives wind producers a 2.3-cent tax credit for each kilowatt-hour...