What happened 

Shares of Sunrun Inc. (NASDAQ:RUN) jumped as much as 17.7% in trading Friday after the solar installer reported second-quarter 2018 results. At 2:50 p.m. EDT, the stock was still trading down 15.6% and showed no signs of recovering today. 

So what

Revenue jumped 30.5% to $170.5 million and net income dropped 59.6% to $7.4 million, or $0.06 per share. The biggest driver of declining net income were a 40.4% increase in sales and marketing costs to $49.2 million. 

Roof with a large solar installation on a sunny day.

Image source: Getty Images.

Wall Street analysts were expecting sales of $168 million, which Sunrun topped, but they also forecast $0.30 per share in net income. The earnings miss is what has shares selling off today. 

Now what

Sunrun has always played a challenging balancing act of trying to limit sales and marketing costs while still growing the business. But customers are becoming harder to find and that's why it's getting more expensive to attract them. We're seeing those costs hit the business hard, and I don't see them decreasing as the company tries to expand its business in the future.