Although we don't believe in timing the market or panicking over market movements, we do like to keep an eye on big changes -- just in case they're material to our investing thesis.

What: Shares of First Solar (NASDAQ:FSLR) dropped as much as 10% today, dragging the rest of the industry down with it. SolarCity (NASDAQ:SCTY.DL) dropped as much as 11% and SunPower (NASDAQ:SPWR) fell 7% in early trading.

So what: The driver today was First Solar's first-quarter earnings, which came in slightly lower than estimates. Revenue of $755 million beat the $725 million estimate, but earnings of $0.69 per share was $0.06 short of estimates.

Now what: The reaction by investors is puzzling to say the least. First Solar reiterated full-year guidance for 2013, which excited Wall Street just a month ago. It's also difficult to draw conclusions from a single quarter because First Solar gets most of its revenue from selling systems, which results in lumpy quarterly results. 

As for SolarCity and SunPower, they're dropping just because First Solar "missed" earnings by a fraction. I think the move is overdone for all solar stocks and investors will return to sanity and start seeing value in the sector in coming months. These are three of the best stocks in solar and the industry is just entering its growth phase.