Only in Cincinnati, Ohio and Wellington, NZ did I have a choice as far as power companies go. Everyone uses the same lines, so it's all about who buys the power and puts it on said line. Wellington had a company called PowerShop where you could buy power "futures" at a discounted rate depending on what you thought you were going to use.

We only have one provider in my current city, but they're super cheap and also provide really good 1G fiber.