Power grids are feeling the strain as the U.S. moves away from conventional power plants. From California to Texas to Indiana, electric-grid operators are warning that power-generating capacity is struggling to keep up with demand , a gap that could lead to rolling blackouts during heat waves or other peak periods as soon as this year. California’s grid operator said Friday that it anticipates a shortfall in supplies this summer, especially if extreme heat, wildfires or delays in bringing new power sources online exacerbate the constraints . The Midcontinent Independent System Operator, or MISO, which oversees a large regional grid spanning much of the Midwest, said late last month that capacity shortages may force it to take emergency measures to meet summer demand and flagged the risk of outages. In Texas, where a number of power plants lately went offline for maintenance, the grid operator warned of tight conditions […]