I made a tactical error at a meeting in one of the region's office buildings last week.
I didn't bring a coat.
I was carrying a digital thermometer, and as the air vents whooshed, it hit 68.9 degrees.
How ironic that with all the concern about global warming, we can't seem to cool it with the cooling.
On a hot summer day, 35 percent to 40 percent of electricity use is "weather sensitive," says Ray Dotter, spokesman for PJM Interconnection, which operates the region's electricity grid.
In other words, mostly air conditioners. (His office, by the way, is 77 degrees.)
Michael Wood with Peco Energy Co. says when daytime temperatures rise from the 70s to the 90s, electricity use spikes 50 percent or more. It's the grid's busiest time of year.
Also the most expensive. Peak energy is priced at a premium. And to avoid brownouts, the grid itself - the plants and transmission lines - have to be sized not for "normal" use, but for the spikes. It's like building all the shore roads big enough for Memorial Day traffic.
Here's the math on conservation: Every degree the thermostat goes up translates to a 3 percent savings in energy and dollars.
So what could be simpler? It doesn't take a government program or a scientific breakthrough. Just press a button.
Around the region, many temperatures are in the low 70s - even the eco-friendly Eagles offices.
At Philadelphia's City Hall, known for its hot atmospherics, Mayor Nutter's office last week was 72 despite a priority to reduce energy use.
So a tip of the sun hat goes to Gov. Rendell, who this month directed that thermostats in state buildings go from 74 degrees to 75. He says it will save 5.3 million kilowatt hours a year - nearly what 500 households use.
Anyone hot and bothered yet? "It's discernibly warm," admits press secretary Chuck Ardo. But so far, no mutiny.
Actually, Rendell's move was minor.
In 1979, President Carter ordered federal buildings to hold at 78. In Congress, Geraldine Ferraro ditched her suits for a cotton jersey dress; Morris Udall formed a Comfort Caucus to "liberate" men from coats and ties.
In 2005, Japan went further, requiring thermostats to be set at 82 in summer.
Neckties were out; lightweight "global warming" suits were in. Talk about sweat equity. And Japan avoided millions of tons of CO2 emissions.
Cornell researcher Alan Hedge has studied warm workers' productivity.
When the temperature rose from 68 to 77 degrees, typing errors fell by more than 40 percent and output jumped 150 percent among keyboarders at an Orlando insurance office.
The results bore out in subsequent studies on Long Island and in New Jersey - and at temperatures up to 85!
They expected productivity to top out at some point. "But so far, we haven't hit that," says Hedge, speaking from his "perfectly comfortable" 82-degree home office.
For now, the American Council for an Energy Efficient Economy likes 78 for households, says buildings program director Jennifer Thorne Amann. "Slightly lower" is OK in offices "because people can't wear shorts."
I realize building managers - and spouses - mess with thermostats at their peril. Brad Pitt made a marriage vow to split the thermostat difference with Jennifer Aniston, and look what happened.
But why not take a cue from Rendell? What about a one-degree difference from wherever your thermostat is now?
It sure would have helped my meeting last week - on "smart energy," of all things. As I sat there, my thermometer continued its descent.
It bottomed out at 68.0.
Here are ways to keep your cool and save energy:
Room or ceiling fans make the air seem cooler.
Insulate your attic.
Pull shades to keep out sunlight.
On central air, install a programmable thermostat that raises the temperature at night or when you're away.
Change air filters every one to three months. Dirty ones make the system work harder.
As outside temperature warms, raise the thermostat indoors.
Seal connections of ducts.
SOURCES: American Council for an Energy Efficient Economy, U.S. Energy Star Program.