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 renewable energy company Advanced Energy Industries (Nasdaq: AEIS) fell 13% today after the company lowered second-quarter guidance.

So what: Management now expects second-quarter revenue to be $137 million to $140 million, down from a previous view of $148 million to $160 million. Earnings per share are expected to be at the bottom end of the previous range of $0.36 to $0.44.

Now what: Poor conditions in the solar market are to blame for the weaker than expected results, according to management. But the weak second quarter isn't expected to hurt the company's long-term strategy as it expects a falling levelized cost of energy to help results in the future. The weak second quarter shouldn't be a huge surprise to followers of renewable energy, so I see today's dip as a buying opportunity for shares.

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