Green Mountain Power will provide you with an estimate, and your local GMP Distribution Designer will provide you with a written estimate. The average cost will vary; however as an example the average single phase overhead is $15 per foot, and the average single phase underground is $16 per foot. Prices are detailed in the Line Extension tariff approved by the Public Utilities Commission. Should there be any changes to the project, the estimate will change accordingly. If GMP runs into a ledge, a new estimate for additional costs will be provided to the customer.