The contract, which is for 50% of the output of the Cape Wind offshore wind facility, sets the initial price – for electricity, capacity, and renewable energy attributes – at 18.7 cents per kWh in 2013, and rising 3.5% annually for 15 years.

After that, National Grid would have the right to a one-time extension of the contract for another 10 years on terms that could be below market rates.

The contract allows for upward and downward price adjustments based on a variety of contingencies.

If Cape Wind is unable to tap certain federal subsidies, the price would go up, but under other circumstances the prices could go down, to the benefit of ratepayers, the DPU said.

The DPU found that the contract and the Cape Wind project will moderate electricity peak load in the region.