New England’s power grid operator said it is ready to meet summer demand for electricity. ISO New England said Monday that under normal conditions of about 90 degrees, demand pushed up by air conditioners could peak at 26,690 megawatts of electricity. In an extended heat wave of about 95 degrees, demand could rise to 28,985 megawatts. One megawatt powers about 1,000 homes. If all power plants in New England operate at maximum output, electricity produced would total about 31,760 megawatts, providing more than enough power. But that drops to 29,580 megawatts to account for power that generators have already promised to sell.