Air conditioning carries a high cost in energy and dollars

One reason more Minnesotans are using more air conditioning more often is Minnesota is getting warmer.

The warming trend is most noticeable at night.

The number of 90 degree daytime temperature readings is actually declining, according to University of Minnesota meteorologist and climatologist Mark Seeley.

The warming trend, Seeley says, happens when the sun goes down.

"The number of very warm overnight lows is getting greater and greater and greater."

In l948, the number of 90 degree or warmer days was just over 16, state climate records show. Last year it was just over 13.

In l948, the number of 70 degree nights was about eight and a half. Last year the number was just over 11.

The warmth from the increase in the number of hotter nights is off setting the decline in the number of warmer days, Seeley says. Part of the explanation for more, warmer nights, is there's more water vapor - humidity - in the air.

"There may be a whole complex of things behind that, but clearly that's a signature change in our climate," Seeley says.

It's not only warmer because of higher nighttime temperatures, it feels warmer because of the water vapor, what Seeley calls the ultimate greenhouse gas.

Mechanical air conditioners make us more comfortable by taking water vapor out as they cool and dry the air.

There was a time when some considered air conditioning un-Minnesotan. Many houses and workplaces didn't have it.

Belinda Manolis lives in a Twin Cities suburban rambler with her children and husband and says they've just turned on the air conditioning for the season. She grew up in a northern Twin Cities suburban family home without AC.

"When it became really unbearable in the drought years of the late '80's we'd just put out our sleeping bags in the basement and sleep there if we needed to," she says.

The picture these days is very different.

Northern Minnesota utilities that used to report their peak electric use was in the winter now report it's in the summer and increased demand for air conditioning is the reason, state officials say.

A government survey two decades ago found 25 percent of the households in our region didn't have air conditioning. Now that number is down to 8 percent with 92 percent of the households reporting they have either central or window air conditioning.

And of course many workplaces have air conditioning. There's a widely agreed on temperature range for work, says Xcel Energy's Shawn White, a business cooling consultant.

"Seventy six degrees is about average. In the winter time, 71 degrees is about the most comfortable," he says.

That means we now have a couple of generations of Minnesotans who think anything outside a temperature range of 71 to 76 degrees is not comfortable.

One writer, Joe Klein, in a recent Time magazine column describes the growth of air conditioning the unnecessary refrigeration of America.

Our craving for coolness is not as common in other places in the world, says Phil Smith, an energy adviser for Minnesota's office of energy security.

People in Asia and Europe tolerate indoor temperatures that would turn some Americans red in the face. But he's noticing a shift in some European countries.

"There is a growing demand for air conditioning because they're experiencing much hotter summers," he says.

If you enjoy numbers here's a sort of air conditioning score card.

Half the country's electricity comes from burning coal.

The federal government says air conditioning uses almost 5 percent of all the electricity produced in the U.S.

The government puts the cost of air conditioning to homeowners at over $15 billion a year.

The amount of energy used creates roughly 140 million tons of carbon dioxide.

One last number.

The federal government says if every room air conditioner sold in this country had the ENERGY STAR conservation rating greenhouse, gas emissions from coal and natural gas fired generating plants would be cut by 600,000 tons.

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