NEW YORK ( TheStreet) -- Solar inverter company Power-One ( PWER) announced after the close of the market on Tuesday that it's beginning a stock buyback program of up to 10 million shares, or 6% of the solar inverter company's 160 million outstanding common shares. Power-One shares could use some support. The solar inverter stock has been the hardest hit of any solar stock since German solar inverter giant SMA Solar said last week that 2011 may be a difficult year for inverter company margins.
Power-One shares are down 22% in the past five trading days -- and were down more than 25% at the worst moment of the decline. Even when Power-One shares staged a comeback on Monday, the bearish pressure sank the solar inverter shares again yesterday. Other inverter stocks took a tumble too, but have recovered since last week, or in the least, cut their losses. SMA Solar is down 7% over the past five trading days, though since it held its annual Capital Markets Day last week, that was probably not the trading response for which the German solar inverter giant was looking. The two other U.S. solar inverter plays, SatCon ( SATC) and Advanced Energy Industries ( AEIS), have minimal losses over the past five trading days -- though Advanced Energy shares are actually down in the year-to-date period by close to 6%, and SatCon shares up only 19.5%, a minor rise compared to Power-One's 140% share skyrocketing this year, at least before last week's share decline. Once the Power-One buyback program was announced after the market close, however, the solar inverter company's shares rallied by close to 4%. Power-One shares were up by more than 4% in pre-market trading on Wednesday, though volume was light. Power-One was by far the biggest decliner in the solar sector last week.