Energien.dk is a Danish educational site for junior high kids, specifically about electricity, gas and energy. It was created for use in Danish schools, and appears to have been commissioned by for an association of Danish energy companies and providers.
 
If you click on the link Kampen om Energien (the Fight for Energy) on that page, you'll find is an RTS style game in which the player manages the use and distribution of electricity during the last 150 years. The player must "build a society" to realize "the challenges faced with when it starts to use electricity, when it has to expand the use because of the development of society in general, and then later try to reduce the use of electricity and pollution" (many thanks to Lisbeth for the overview and translations!). I can only get so far because of all the Danish, but the game seems to be well put together with good production value. One of the problems with educational games is that they often fail to take advantage of the standards and conventions of videogame genres. Kampon om Energien seems to borrow directly from standard RTS conventions, which makes a lot of sense for this kind of game.
 
You can also try out Legen med Energien (Play with Energy) is a series of small "interactive physics set-up tests and assignments" to be used alongside a textbook.
 
(thanks to Nico for the tip and Lisbeth for the Danish help)