By all accounts, September was a great month for stocks. The S&P 500 gained 8.8%, making for the best September since 1939. The month was particularly kind to A-Power Energy Generation Systems (Nasdaq: APWR), which saw the stock rise 45% off of its August close. I guess that answers my question.

A-Power investors have indeed caught a break, as overly negative sentiment was dispelled last month (last week, mainly) by a series of announcements. Mid-month, we saw a press release about a feasibility study on a biomass-fired power plant in Nevada. That one didn't really generate much enthusiasm.

In contrast, A-Power brought us three pieces of news last week that really lit a fire under the stock. Tuesday saw the announcement of first production of a prototype wind turbine destined for the company's wind project in Texas. On Wednesday, A-Power announced a $279 million engineering, procurement, and construction (EPC) contract for a Chinese hydropower project. Revenue will be recognized over the course of the six-year project on a percentage-of-completion basis. Finally, on Thursday, A-Power announced an additional EPC win for its core distributed generation business. This contract is worth around $36 million, and should take fewer than two years to complete.

Taken together, these pieces of news don't actually tell me a ton about the long-term viability of the business. The prototype news doesn't tell me that the wind farm project is a lock. A formal financing agreement would have been far more monumental. As for the EPC deals, those are A-Power's bread and butter. Power plants are the firm's core competency, and the awards are pretty much business as usual.

As I suggested in late August, A-Power was too cheap, and this near-term break was likely. I had no idea the mispricing would correct so quickly, however -- or on news that was, in my opinion, incrementally positive, but nothing earth-shattering. It's interesting that one of the stocks I chose to make the case for A-Power's undervaluation, Duoyuan Global Water (NYSE: DGW), had a brutal fall following accounting irregularities at related company Duoyuan Printing (NYSE: DYP). A-Power suddenly trades at a premium to the former highflier (which I flagged as "seriously expensive" last year), on the basis of trailing sales.

So where do I stand now? Now that the stock has rebounded so significantly, I'm a lot less interested in A-Power as a potential short-term speculation. Sure, it's still cheaper than Chinese cleantech stocks like JinkoSolar (NYSE: JKS), but that company has one of the best cost profiles in the solar industry. As for a long-term investment, A-Power has never met my growth stock criteria.

Fool contributor Toby Shute doesn't have a position in any company mentioned. Check out his CAPS profile or follow his articles using Twitter or RSS. The Motley Fool has a disclosure policy.