Tight supplies of natural gas, crude, and coal have pushed up residential electricity rates this year. A nationwide weather outlook for this summer forecasts extreme heat — all of this will force households to crank up their air conditions, resulting in oversized power demand that could stress national grids.

Bloomberg cites new data from Barclays Plc that says monthly power bills could be 40% more than last year's. The US Energy Information Administration expects retail residential electricity rates to increase the most since 2008.

Data from the US Bureau of Labor Statistics shows Miami households spent 38% more on energy in April than a year ago. Power prices in the state have jumped due to the rising cost of natgas.

"Our continued overreliance on gas only sets us up for these burdensome and unnecessary rate increases. 

"This business model is unsustainable, and it's hurting people," said Natalia Brown of Catalyst Miami, a nonprofit consumer advocacy group. 

Besides Miami, parts of Hawaii, Dallas, Minneapolis, Boston, Philadelphia, New York, and San Francisco recorded the highest increases in retail electricity costs last month.