Mid-December 2010 Temperature & Energy Use Report for Forsyth Missouri

Forsyth, Mo. -  My intent is to post temperature information I have been gathering as part ongoing research for a book on home energy saving practices due out sometime in March 2011.

The graph displayed above represents temperature data taken for my home here in southwest Missouri. The data for the previous year of 2009 was gleamed from a fellow weather watcher over in White Tail Crossing, a location just to the north of Branson, Missouri.

The major difference between last year and this year is the fact that temperatures, on average, have been much lower than they were in 2009. This is true, at least through the first two weeks of the month. Plotted in the graph above are the mean temperatures for each date which represents the average of the highs and lows for that twenty-four hour period. (I posted these and not the actual highs and lows as they are more indicative of trend analysis. The actual values are posted on the left side for anyone who is interested).

As you can see this year’s average temperature, through the middle of the month, is 3.8 degrees Fahrenheit colder the thirty year average. I think for there to be any significant difference of more than say a tenth of a degree when compared to thirty previous December is significant in and of itself. (Whether this is indicative of a long term change, a blip or one that will average itself out over the balance of the month remains to be seen).

Likewise, the energy used to heat my home is also trending upwards in line with the colder air outside. Last year, I used 2,074 kilowatt hours and the year before that (with the average mean temperatures close to normal) 1,878 KWh. This year, in spite of efforts to better insulate my home, I am trending to come in at 1,978 KWh (63.8 times 31 days) which would only be marginally below last year. Colder than normal months can be significant to anyone on a fixed income when considered on top of a 13+ percent rise in the cost of electricity we received in my county earlier this year. (As a side note, the Springfield weather office is reporting an even larger seven degree mean temperature variance this year versus average).

Precipitation for most of the Taney county-wide area has also been a little sparse. Most sites have recorded around a tenth of an inch or less since the first of the month. In a normal year, we should see somewhere between three and four inches,

The bottom line, so far, is a month that is colder and dryer than usual. However, the weather service is hinting at a moderation of temperatures for the later weeks of this month. Now if we just get some rain!

Anticipating my electric bills based on mean outside temperatures.

For all of December, I have been recording the temperature in three major rooms of my house (Living room, Dining area and Master bedroom) three times a day in order to get a feel for the average temperature that is maintained 24/7. I have had the thermostat set between 69F and 70F for the entire period. The end result of all this measuring has been to determine that the average temperature for the core of my home has been 68F.The central unit used to heat my home is a heat pump. There are also a couple of small space heaters that are used as needed.

Since I now knew what the average level was inside and had also recorded the average outside temperature from day to day, I was able to construct the graph pictured here. On the left side is power use expressed as kilowatt hours while the X axis displays what I call ‘load’ which is merely the difference of the average inside temperatures (68F) minus the average outside temperature for any given day. I then graphed each day as a point in a spreadsheet expressed as an x-y scatter diagram. To this set of data, I have applied a trend line that is extend backwards twenty units. As you can see, there is pretty close agreement when comparing the kilowatt hours used to daily average temperature (the R-squared value was 0.9101). This graph then, gives me a pretty handy tool for anticipating not only the cost of electricity for a particular day but also for a week or a month.

As I have data for the first thirteen days, so then do I also have a pretty good way to guess that this month will end up with an average temperature of somewhere between 32 and 37 degrees Fahrenheit ( the fifty percent statistical spread around the historical mean temperature of 35F that is left for the remainder of the month). Therefore, at ten cents approximately a kilowatt hour for electricity, I can assume a month end bill of between $186 (60KWh x 31) and $211 (68 x 31). An interesting side note to this experiment is the points that fall either above or below the trend line. I will assume that a point above represents heavier than normal use of appliances while those below, less. This is due to the fact that when measuring the power consumed for each day, I had to measure the total power used by all the electrical devices in the house, not just the furnace. Hope this made some sense.

December temperatures can be tough in SW Missouri!

While winter officially gets its start on December the 21^st, I’ve always felt that it really started on the first and then lasted through the 28^th of February. As you can see in the graph above we get some pretty cold December nights even this far south in the mid section of the country. Note that the data was obtained from a Davis weather station located just north of Branson, Mo.

My energy usage for 2009 in kilowatt hours was 2070 KWh, which I felt was a bit on the high side. As I pay about ten cents per KWh, that meant a bill over $200 for the month! If you average out the power, it equates to an average expenditure of 66.8 KWh per day. The year before (2008) I used 1878 KWh although that month was pretty average coming in at a mean temperature of 35.7F. while 2009 was a much colder 33.6F.

Since I heat my home with an air heat pump (which work in temperatures only down to a certain point), I know that the auxiliary heat will come on whenever the outside temperature hits about 35F. That’s pretty often for December, so one of my plans will be to use space heaters in the living area and bedroom to supplement the heat pump. The theory being that by using space heaters which are more efficient at delivering warm air to a particular room than the heat pump is, I will actually be saving some energy. That’s the theory anyway. The trade off will be to keep the need to keep the house thermostat set to a low number (perhaps 70F) which will insure the other rooms that do not have space heaters will be pretty cold. I’ll see how that actually works out as I go through the month which starts tomorrow.

The other affirmative action measures I have taken have been to cover some windows with 3M plastic insulation and to make sure that unnecessary electrical devices are turned off. I’ll follow up with a report at the end of the first week to report on how I’m doing.