You can use free geothermal air conditioning with your current central AC, here's how to do it.

Much of the country is in a heat wave. It's been in the 90s and triple digits here the last couple of days.  Yesterday, Lisa turned on the central AC in anticipation of another hot one.  We limit our AC use, this was the first time this year to break down and start it up.  There were blackouts and reports of extreme stress on the power grid.  Lots of people out there using a lot of AC energy.

Well, here's the thing.  Though I didn't tell her, when she turned on the AC, she did so at the thermostat and did not include the outdoor breaker at the compressor.  Without it, no AC.  So, I opened the basement cold air return register and let the duct fan, activated by Lisa's thermostat action, blow.  The basement, cooled by shallow passive geothermal action (in New Hampshire, the earth below 5-6 feet is at 52-53˚F all year) remains cool.  The basement air, drawn into the duct system, circulated through the house and kept the place cooler throughout the day during the highest electricity demand. 

By 8:00pm as the day had caught up with the basement's ability to cool the house (and Lisa was feeling it), I kicked in the real AC,  dropped the house temp down 4 or 5 degrees, dropped the humidity, and we were good for the night.  This morning, I switched back to just the fan (on circulation mode which doesn't run the whole time) and we are saving energy and helping out the power grid again today.

If you have central AC, give it a try.  Any amount of time not running your AC compressor saves energy and money.