When air-conditioners kick into overdrive on a hot afternoon, the price of electricity rises dramatically. Heavy air-conditioning usage can also prompt brownouts and blackouts. To get around it, companies such as Comverge, of East Hanover, N.J., and EnerNoc, based in Boston, have created systems that effectively redistribute electricity between buildings and appliances on a grid. If a brownout is looming, swimming pool heaters might be turned down so that air-conditioners can go full throttle. The systems save money too by cutting back on power usage in the afternoon, when rates peak. Utilities in Utah, Florida and other states have begun to install these systems.