Friday, June 20, 2014

Energy savings in the summer time is challenging!

Forsyth MO - In late June, every year, I always grow a little bit concerned about how much money my heat pump is going to burn through just to keep my house cooled down to a still warmish 82°F. With electric rate recently increased to a summertime rate of 0.1149 cents per kilowatt hour (up from .1070 or a 7% increase), I want to make sure I'm doing all that I can to keep my electric bill as small as possible. Note that the Empire Electric Coop also tacks on a $12.52 usage charge to every monthly bill!

In July, down here in southwest Missouri, we can often get into the low to mid nineties (average high is 89°F), with oftentimes lots of humidity to make things even more uncomfortable. From past experiments, I've already ascertained that when the temperature hits the 90 degree mark, it will typically mean a 30+ kWh power use day to run my whole house and to cool it down to 81°F. Last year, the temperature hit 90+ over 16 times in July! The only thing that save me that year was a surprise cool down toward the end of the month! My total power used, that year, was 674 kWh. That would relate to a $90 electric bill at todays current rates.

Forsyth MO temps for July 2013
The Plan

So, what's my plan for this summer? I want to keep my electric cost as low as possible without frying in the process. I've considered a couple of alternatives, including purchasing a small portable AC unit to cool just my man cave. This unit has a dual function in that it both cools the air and dehumidifies! The SPT 8,000BTU Single Hose Portable AC unit pictured here, sells for $288 on Amazon. The problem I have with this approach is that it also uses power!

A second approach to saving on energy would be to utilize my basement on the really hot days. The air down there typically runs at about 67°F all year long. It's a finished basement complete with a bedroom and a bathroom, so I may just plan to move down there and see how that goes. Stay tuned for more!

Wednesday, June 18, 2014

My power use for the first really warm day of late June!

For anyone who lives on a fixed income, you live or die based on variable costs like electricity which can fluctuate by as much as 30% from one month to the next. In general, we all get a break twice a year; in the spring and then again in the fall when neither the furnace or the AC is running.

Thus far, I'd been able to skate by with my AC in the off position until the 17th of June when it began to get seriously hot. By noon on that day, the temperature outdoors read 86°F and seemed headed for 90 or so by the late afternoon. The relative humidity read 60% and that more than anything else prodded me to turn my heat pump to cool to 81°F. In my room, at that time, the reading was 83°F which felt a bit warm. I was running a ceiling fan which helps up to only a point. I had been averaging 15.3 kWh thus far in the month, but felt sure that was going to change upwards pretty quickly! (I was, in point of fact, trending towards a total power use of about 582 kWh through the 16th. The would equate to an electric bill from Empire Electric of only about $80).

At 12:00 Noon, I noticed I had used 8.8 kWh of power (since midnight) which was not too bad. At that rate (.733 kilowatts per hour) I could normally expect to finish the day at about 17.6 kWh which would be very doable and in line with the monthly average. (That was not be the case, however).

Quite often in the early summer, we get pop up thunderstorms that serves to cool everything down before moving on. It's not unusual to see the temperatures drop twenty degrees or more as the rain transports cold upper air down to the ground. Unfortunately as you can see at right, the radar over southwest Missouri was not looking very promising!

A fourteen hundred square foot home such as the one I live in and which is a stick-built ranch style dwelling with a basement (cooling effect) – I can normally expect a buffering effect from the outside temperatures to last for a couple of hours after the temperature gets much above the cooling level set for the AC – or, in my case, 81°F. On this date, we hit the 81'outside' degree mark at 9:54 AM. The AC kicked on, for the first time at 11:01 AM and then kicked off at 11:39 AM (see graph). Poof! A few kilowatt hours of power spent on cooling! Of note also was an attic reading of 108.9 degrees! So, above my head was that kind of head while below in the basement it read 65°F. A temperature that is maintained pretty much no matter what's going on outside! And, there I was stuck in the middle!

12:43 PM – AC kicked on – outside temperature was then at 86.6°F. Inside was 83.8°F. Attic reading was 110.7°F. Clouds were increasing a bit – the sky was at about 50% coverage. AC was on for 1 hour.

3:00 PM – The temperature outside was 89.2°F. Inside, it was 82.6°F with an attic temperature of 115.2°F. Power use at that moment was 13.2 kWh. At 3:10, the AC kicked back on. The temp out was then 90°F.

The AC kicked on two more times – at about 5PM and 7PM, at which point things cooled down enough to retire its operation for the balance of the day. The total power used was 26.2 kWh. Assuming that 15.3 kWh was average, this meant I used 10.9 kWh for cooling. This come to about a buck in terms of cost.