programmable thermostats

Okay, at last the electric bill arrived. This is the first full month’s summer bill I’ve had since I replaced the dratted programmable thermostat with a plain boring digital thermostat. So! The question is…

Did replacing the programmable headache thermostat with something that does not require advanced training in computer programming result in bankruptcy?

And the answer is…. Well, define “bankruptcy.”

The August 2009 bill, when the programmable thing was supposed to heat up the house during the day and cool it down at bedtime and then let the temperature drift back up when I would supposedly be unconscious in bed, was $257. Since the highest summer bill in previous years had been $229 and rates had held steady for several years, that was pretty darned breathtaking.

Since then, Salt River Project has raised its rates about 10 percent. So, in theory, this month’s bill should be around $282, approaching break-the-bank levels.

And the real bill WAS... $239.08!!!!

Wooo-HOOO! Almost $20 less than last year’s monster bill, in spite of the rate hikes!

Isn’t that something? This summer has been a little cooler than 2009, but not much—we’ve still had long stretches of 110- to 115-degree days. Except for the last two weekends, when rains drove early-morning temps into the 80s, the AC has been pounding away, all day and all night.

I figure the difference has to do with the thermostat, since the midsummer weather doesn’t vary much from year to year. After the programmable thing was installed last year (May 2009), the June bill was $49 higher than the June 2008 bill; the July 2009 bill was $36 lower, and the August bill was $28 more.

After seeing the June gouge, I ratcheted the temperature in the house way up, and so that may explain the drop in July. But I didn’t turn it down in August—and in fact, August is usually less scorching than July. And August 2009 cost almost $30 more than the prior August. So there’s no clear explanation for the $36 saving in July of 2009.

April and May were temperate this year, and so the bills that came in May and June were fairly low, reflecting the fact that I left the AC off most of those two months. June started to heat up, so the bill that arrived in July shot up through the roof: $11 more than the same month last year.

The programmable thermostat came off on July 2, and so the bill that came today is the first non-programmable thermostat month of 2010: $20 less than the bill for the same period in 2009.

How did I work this little miracle without the wonders of the silicon chip?

This new thermostat has a function called “Save.” When you press the “Save” button, it remembers the setting you started with but pushes up the temperature in the house by five degrees. So, I’ve had the thing set at 79 degrees for nighttime use, and, as soon as I stumble out of bed, I’ve been hitting the “Save” button on the way to the bathroom. This keeps the daytime temperature at 84.

That’s approximately what I was doing with the programmable thermostat, only ratcheting it up to 85 during the day, down to 76 around 6:00 p.m. so it would be cool enough to sleep by around 9:00 or 10:00 p.m.,  and having it go back to 80 about midnight.

So really, now there are more hours when the temperature is in the tolerable range (85 really is uncomfortable in a shut-up house full of stale air) than with the programmable number, but the bill is significantly lower.

Yesterday morning Matt the Air-conditioning Tech called to discuss the thermostat issue. By then I had finally managed to figure out the trick of programming the thing, evidently quite the trick, since one of the instructions he gave me over the phone was wrong. If an expert can’t work it, I don’t feel like such a moron taking months to master its “simple” instructions.

Matt said the classic round Honeywell thermostat is no longer being made: mercury. He speculated that before replacing the programmable number with another digital thermostat, it might be worth it to experiment with jacking up the temperature further during the day or simply turning the system off until the house starts to get uncomfortable. That mimics what I used to do with the old thermostat: I would turn it off manually the first thing in the morning and leave it off till I couldn’t stand the heat any more, or, on workdays, until I got home from the office. 

Hilariously, Matt suggested one way to shut the fancy thermostat off: press the “Hold” button. He believed that would turn it off until the button was pressed again.

N-n-o. What that does is say to the system “hold the temperature at the figure that’s now showing on your display, no matter what the programming says.” So, if your system is set at 80 degrees from 9:00 a.m. to 6:00 p.m., the thermostat reads 78 (meaning it registers the temperature at 78 degrees), and you press “Hold,” the device will keep the temp at 78 degrees. Should you notice this fluke and press “Hold” again to toggle that function off, the thermostat will go back to maintaining the temp at 80.

It now looks like the issues are these:

• The thermostat Matt installed isn’t really a model designed for heat pumps, even though he insists it’s perfectly OK with my system.

• It’s apparently more sensitive than the old round Honeywell number. The formerly oven-like bedrooms have been, it must be admitted, suspiciously balmy. To get them that way, the thermostat runs the unit longer than the old one did.

• Eighty degrees is too cool. I need to set it for about 82 in the daytime and then leave the system turned off until it gets unbearable inside the house. That evidently saves more power than programmed setbacks.

Mercifully, just now we’re having a cold spell. When I got up at 5:00 this morning, it was a fantastic 70 degrees outside, after a night that allowed me to leave the AC off and the window locked in its no-burglar-can-squeeze-through open position. Today is supposed to be cool—only about 90—followed by another 70-degree night. w00t!