By David Roberts, Vox.

Back in December, Congress did something it rarely does any more these days — struck a series of compromises and passed a bill, specifically a giant $1.8 trillion spending bill.

Among many other things, that bill extended the two key federal tax credits that support renewable energy: the production tax credit (PTC), which mostly goes to wind, and the investment tax credit (ITC), which goes to solar.

It went by quickly in an otherwise news-packed month, so it's worth pausing a moment to note that for US renewable energy it was a very, very big deal.