GMR Infrastructure (up 7.59%), Reliance Power (up 5.73%), Lanco Infratech (up 5.03%), Tata Power (up 4.14%), Reliance Infrastructure (up 4.02%), GVK Power & Infrastructure (up 3.25%), Adani Power (up 2.84%), JSW Energy (up 2.14%), NTPC (up 1.43%) and Torrent Power (up 0.41%), edged higher.

The BSE Power index was up 3.01% at 1,977.03. It outperformed the Sensex, which was up 2.19% at 17,362.15.

The BSE Power index had outperformed the market over the past one month until 28 June 2012, gaining 5.10% compared with the Sensex's 3.50% rise. The index had, however, underperformed the market in past one quarter, falling 6.71% as against 0.76% fall in the Sensex.

According to reports, the spot coal prices globally are down 20-30% from their year ago levels and almost 40% below their peak in early 2011. The benchmark Newcastle, Australia thermal coal is trading around $87 per tonne in June 2012 - a two-year low - as against around $142 per tonne at the beginning of 2011. Similarly, the Indonesian Coal Reference Price is trading around $96.65 in June '12 from a peak of $127 in early 2011, reports added.

Fall in international coal prices this year could boost profitability of those power generation firms which buy imported coal in the spot market. Coal is the largest source of energy for electricity generation.