Utilities group National Grid has agreed with Long Island Power Authority to modify and extend their power supply agreement for at least another 12 years. National Grid owns and manages a number of power plants on Long Island, with a generation capacity of 3,700 megawatts. The company has been supplying that electricity to communities and businesses across Long Island since 1998, under an agreement with Long Island Power that is currently set to expire in May next year. Once all regulatory approvals are received, the new agreement would give National Grid and Long Island Power new options for updating and modernising the power plants through retiring, or "repowering," existing facilities while reducing energy costs and improving environmental performance.The share price rose 0.65% to 699.50p by 13:22.NR