Activists from Canada, Britain, Germany, Poland and Sweden would stay perched on the chimney "until Poland's prime minister promises Poland will not block the EU's climate package," Greenpeace spokesman Jacek Winiarski told AFP.
Greenpeace also hung a banner reading "Quit coal, save the climate" on the smokestack at the brown coal fired power plant near Konin, in central Poland.
The protest comes a day after high-profile UN Climate Negotiations opened in the nearby western Polish city of Poznan.
A 2004 EU entrant, Poland, which depends on coal for 94 percent of its electricity, supports the objectives of the EU's planned climate package, but has refused to agree to its terms arguing they would see energy prices skyrocket and so thwart economic growth.
The EU climate package, which the 27-member bloc is expected to adopt at its December 11-12 summit in Brussels, sets industrial targets of giving renewables a 20-percent stake in the electricity market, reducing CO2 emissions by 20 percent and increasing energy efficiency by 20 percent by 2020 compared with 1990 levels.