Only 17 states, plus the District of Columbia, have protections that prevent utility companies from turning off the power of people who fall behind in their bills. But they only take effect when temperatures hit a certain level or when a heat advisory is in place, Wolfe said. For Nevada and Delaware, for instance, that threshold is 105 degrees.

This compares to 33 states and the District of Columbia that prevent utilities from shutting off the heat during the winter.

Nearly all states and the District of Columbia provide some protection for residents with certified medical conditions, though many only delay the disconnection for 30 days.

Still, many people whose health is compromised by hot temperatures don't qualify.

Though he suffers from a thyroid condition that makes him very sensitive to heat, Walter Protheroe now sets his air conditioner at 78 degrees, instead of a more comfortable 72 degrees. That keeps his electric bill affordable since he's disabled and living on a fixed income.

But it means the 64-year-old Houston resident has to spend most of the day lying down on the couch. He can only take short walks outside twice a week, instead of his daily one-mile stroll, because he can't return to a cool home in a city contending with its hottest summer to date.

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A former research engineer, Protheroe thought his June bill would be around $90, but it was $125. He's expecting to have to shell out about $150 this month and probably more than $170 in August if the heat continues.