As others have said, it depends on many factors. The proximity of the lines to the home, the size of the lines and the poles or towers, is there also an unsightly power station there?
In any event, a home close to power lines will cost less to buy, but will also fetch less when sold. Some buyers may not mid th lines at all and be thrilled by the discount, knowing that they will have to discount when they do sell.
My most memorable personal experience in selling such a home came at the bottom of the housing crisis a couple of years ago. A beautiful Drees home in north Plano, which I am sure would have otherwise gone for $350,000 was finally sold after a lengthy listing for $300,000. I don't believe the discount would be as steep in 2010. The house was immediately adjacent to a greenway with huge power poles.