How to trade Power between Cities?

Solution 1:

Lets call the city that buys Power as BuyerCity and the city that Sells power as seller City. Here are the things to note before initiating a power deal.

1. Make sure BuyerCity and SellerCity are neighbours!
2. Build Power plants in SellerCity.
3. Build power lines to SimNation(edge of map towards the buyer city) in SellerCity.
4. In BuyerCity you should see some power lines towards edge of map to SellerCity.(Do not demolish these. This represents the connection to the other city.)
5. BuyerCity must have enough cash on hand to pay for the power. (Possibly need enough cash to fund the deal for a year)
6. BuyerCity must need power. Check the power graph. (Possibly has a deficit or a surplus of less than 1000 MW)
7. Go to budget panel and click on it to get budget overview. Here you can now initiate a power deal with the SellerCity by clicking on Neighbour Deals(In the reds section).

Hope this helps.

Solution 2:

To make the initial deal, there can't be other sources of power in the buying city. So if you've built a windmill, for example, you'll have to bulldoze it before a deal can be made. After the deal starts, rebuild your windmill. I only had to do this on the first buy, later ones with the windmill present worked fine.