You know from reading my blog on household energy consumption that heating and air conditioning make up almost 50% of your energy usage.  And once you know that, it is fairly obvious that outside air temperature would be the biggest influence on how long you have your air conditioner or heat on.  But wouldn't it be nice to see the actual data that backs this up?

Luckily, you can do that!  Well, as long as you have some method for knowing how much energy you use each day and what the average temperature outside is each day.

To figure out how much energy you use each day you will need to use one of the below methods:

• Go outside and read your meter every day at the same time (cheapest but most time consuming)
• Install a home energy monitoring system like the TED 5000 (costs money but easiest and most informative)
• Use your utility installed smart meter connected to the smart grid (the best solution but only available to people who live in areas with forward thinking utilities and people who live in the future)

The method I have used for my comparison is the TED 5000 and the Footprints software that comes with it.  The software enables you to pull history data showing how much energy (and much more information) that you used each day (it even goes down to hours and minutes).  For my comparison I chose to pull the energy consumption for the entire month of August.

Once you can get your energy data, you need to find the outside temperature data for where you live.  Lucky for you, I have made this easy to find with the blog I wrote on finding your city's temperature history data yesterday.  The temperature data is courtesy of Weather Underground.  I found this site when I was researching degree days and found the site degreedays.net who use weather underground for their data.  That blog on degree days will be coming in the near future.

Once you have your energy data and temperature data, you are ready to combine them in an a spreadsheet (I used Excel) and make some graphs to really compare how outside air temperature impacts your energy consumption.

And without further adieu, here is my graph of temperature and energy consumption for each day in August 2009 (the Excel file used to generate the graph is found at the end of this post).

How Temperature impacts Energy Consumption

The actual data is a little scattered for many reasons.  The peaks are probably due to days we did laundry (the dryer consumes a huge amount of electricity) and the lows are probably due to days we weren't in the house much (like weekends and late work nights).  This is why it is necessary to add in the trendlines to get an overview of the relationship in temperature and energy consumption.

The hardest part about making the graph from the Excel data was remembering how to display the data using two y axes.  To do this you have to right click on one of the data series, then select "format data series".  In the window that pops up select the "Axis" tab, then select the radio button for "Secondary axis".

Keep in mind that this is only one month displayed, so I will do this in another few months (once Autumn kicks in) so I will have a larger sample size to show the relationship a little bit clearer and over several months.

Overall you can see that as the average daily temperature decreased over the month of August, the energy consumption declined as well; which is exactly what we all would predict to happen.  Sometimes it's just nice to be constantly reminded of this fact so we all can continue to take efforts adjusting our thermostats, insulating our houses, and being vigilant to reduce energy consumption so we can improve our environment and save money!

mapawatt_blog_temperature_energy_data_091309 : Excel file used to generate above graph.