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 inverter maker Power-One (Nasdaq: PWER) fell 11% today after the company released earnings for the first quarter.

So what: Revenue fell 8% to $226 million but still topped estimates of $204.2 million from analysts. But the bottom line was much worse, with profit falling to $5 million, or $0.03 per share, from $0.30 a year ago. Analysts expected $0.08 per share in profit.

Now what: It's a dog-eat-dog world in the solar industry right now, and inverter manufacturers are feeling the pain that module makers have been dealing with for more than a year. The company is expecting a strong second quarter as people install solar before feed-in tariff cuts, but my concern would be after that. Inverter competition is just starting to heat up, and I don't see anything that indicates Power-One will increase profitability in the short term, which could leave shares out to dry.

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