NOTE: it is assumed in this post that you know how to play Power Grid; I only describe the adaptation here. If I ever collect these posts into a book, I'll expand this one with a complete set of rules.
Power Grid was designed by Friedemann Friess, and is undoubtedly copyrighted and trademarked by him or his publishers. (Last week's game, Pit, was designed by Edgar Cayce.)
The following has not been playtested. Undoubtedly, some tweaking in the number and/or plant powers will need to occur. This can be discovered during the first play or two. Since the plants are acquired through an auction, this should not prevent the game from being playable as is, because, however good or bad a plant is, there is some price at which you hit the pain point.
How to Adapt
Remove the 10 through A from both decks (these will become the power plants). Shuffle the remaining 64 cards and deal them out in the following pattern (only the letters, not the .'s; you can use some of the extra cards to maintain the other cards' positions):
Set aside any unused cards. Each letter represents a region, each inidividual character is a city. The connections between any two diagonally adjacent cities are the sum of the price of the two cards (i.e. somewhere between 4 and 18). Any two adjacent identical cards represent a metropolis and have a connection cost of 0. Choose the correct number of regions in which to play (3 to 5).
The 10's through A's form the power plants. Clubs are oil, Diamonds are coal, Spades are garbage, and Hearts are nuclear. Prices start at 3, and ascend in order: Clubs, Diamonds, Spades, Hearts, and then skips one. So:
TC = 3
TD = 4
TS = 5
TH = 6
JC = 8
JD = 9
JS = 10
JH = 11
The plants are as follows:
+ Nuclear plants require one less fuel. Nuclear plants may also be bought as green plants, adding 4 to the cost.
- Whenever two cards of the same exact rank of Clubs and Diamonds are both available, a hybrid plant may be bought for +2 cost over the coal price. Take either one of the two plants and add an unused face down card underneath it to indicate that it is a hybrid.
Starting plants: Arrange 4 10's and J's of each suit for the starting plants. Remove plants as usual according to the number of players. Mix the rest. When placing plants under the deck, place face up. When you reach the first face up plant, mix and start stage 3 as usual. Cycle plants as usual for Power Grid.
Use 4 different colored tokens to represent the four different types of fuel. Group in 3's at the bottom of the board (which has 9 cards width) to indicate prices.
Houses: use the same tokens as you used for fuel, if you're careful to keep them separated. Track money using pencil and paper. Arrange tokens at the left of the board to indicate player order. You can use the top and right of the board to keep count of number of cities, if required.
Replenish fuel supplies according to your favorite Power Grid chart, adding one additional nuclear fuel in the second and third phases. Use the usual payout chart from PG. The win conditions are as usual in PG.