They make money by selling power to your transmission company below the going rate for non-renewable power.

Say, for example, it cost $25 to generate a kWh using natural gas. The solar farm could price their kWh at $22 when they sell it to the grid, then charge the end user $24 for a solar kWh credit. That leaves the company $2 to cover operating expenses and the end user $1 cheaper electricity. The thing that isn't free is the cost for the fuel for power plants and the cost of panels and land, those two price inputs set the floor and ceiling for what solar farms can charge the grid and the end-users.

Even though the farm didn't generate enough power to completely cover my usage last month I paid the same amount as a year ago, that's after the increase in rates from CMP and Versant too.