What happened 

Shares of residential solar installer Vivint Solar, Inc. (VSLR) fell 5.3% in November, according to data provided by S&P Global Market Intelligence, after reporting third-quarter earnings. It also doesn't help that potential tariffs and tax changes are hanging over the solar industry. 

So what 

Installations were 47 MW and Vivint Solar booked 53 MW in the quarter. Costs rose to $2.94 per watt from $2.88 a year ago and management said costs in the fourth quarter would be $2.90 to $3.00 per watt. 

Large rooftop solar system on a home.

Image source: Getty Images.

The overarching problems facing the residential solar industry are also hitting Vivint Solar. First is the threat of solar tariffs by the Trump Administration, which could hit early in 2018. The tax bill making its way through Congress could also negatively impact residential solar by making it difficult for banks and corporations to provide tax equity financing

Now what 

It's hard to see a scenario where costs don't go up for residential solar companies in 2018 and that will make it harder to sell solar systems economically. That could mean lower installations or less value creation per watt. Those factors are weighing on shares of all solar stocks right now.