From the publisher's website:

Two new maps for Power Grid. This is an expansion pack, so you will need the Power Grid game to play with it. As with the original, the board has a different map on each side: Benelux on one side and Central Europe on the other. Along with the maps are small rule changes to reflect the power culture in these two countries. As the Benelux countries support ecological power, players may have greater opportunities to acquire such power plants. Also, oil is more available and coal less available in these countries. As Poland has large coal supplies, coal will be much more plentiful then elsewhere in Central Europe. However, due to political stands taken by some countries, players may be limited in their access to nuclear power. The result is not just new maps, but new ways to play this great game!