Heating degree days, weather extremes, and thermostat temperatures

The latest power bill arrived last week. January is usually the coldest month of the year and last year was particularly brutal. We used 2102 kWh during last year’s billing period for January. January here usually averages 1107 heating degree days (HDD: the number of degrees in which the day’s average temperature is below 65 °F/18 °C). Last year we had 1291 HDDs with record-breaking lows for many days; this January had only a few more HDDs than average at 1133 and only a single record-breaking cold day on the 8th. This January the billing period was only one day shorter, but we used much less electricity: 1252 kWh for this milder month. The downstairs minisplit thermostat was set a bit lower than last year, but mainly we have avoided the string of record lows of last winter so far. The minisplit heat pump works more efficiently when the temperatures do not approach its -13 °F (-25 °C) low operating temperature. The larger the temperature difference between inside and outside temperatures, the larger the heat flux through the windows and walls of the house, too. Of course, the only control we have in narrowing that delta T is by setting the minisplit temperature as close to the outdoor temperature as possible. It is always nice when the weather cooperates to make that outdoor temperature closer to comfortable!

A milder, more usual January also means that the annual energy usage now is only 7914 kWh, or 10.8 kWh per person per day on average. Last February was also brutally cold whereas this month is shaping up to be more the norm. It will be interesting to see how the house performs in an average year after the initial year of unusually high HDDs to find out what might make sense in terms of solar panels.

Year one kWh’s: The start of a great new year!

The power company just emailed me my latest bill yesterday after the meter reader came by on December 27. I was likely their only customer that was super excited to see the latest charges. :) The year started out with an unseasonably cold and snowy winter, a mild summer, and more heating degree days than usual again in November. Given the many guests that have visited in 2014, the house has had two occupants on average every day of the last year despite our absences. In other words, I could now see if the house and our life in it matched the 13 kWh/day per person design goal.

In logging on to find the meter reading on December 26, 2013, I was very happy to see that we even beat our goal. (You were right, Larry!). The 366-day period saw 8764 kWh of usage—or 12 kWh/per person per day. Yeah! As expected, most of the usage came in the 6-month heating season. Some of the kWh’s were still used by construction and landscaping crews in 2014, but that usage likely contributed little to the total. Overall, the house has performed very well and is much quieter and more comfortable than a less airtight and insulated structure. (The two minisplit heat pumps also contribute to the quiet compared to a forced air furnace system.) The many south-facing windows obviously lead to some heat loss even with triple panes of glass, but have also been a blessing of light in these seemingly nonstop gray days of December. Even without more seasonable temperatures, we will likely come in with even lower numbers in 2015 now that we have a better idea of how to use the ERV and set the temperatures of the minisplit systems on each floor. This power bill is a very nice way to end the first year of this housing experiment.

Thank you to the thousands who have stopped by this blog over the years and kept me writing and to all the people who helped make this house possible. Wishing you all a very happy, cozy 2015!

Cobbles and peonies

Fortunately, the expected rain did not arrive till after dark, so there was more time in the suddenly warm day to work outside. Quarter minus was used to fill the area between the stones in the path to the back deck.

Fortunately, the expected rain did not arrive till after dark, so there was more time in the suddenly warm day to work outside. Quarter minus was used to fill the area between the stones in the path to the back deck.

The driveway and path are now complete! It is too late in the year to do much landscaping, but I did order a dozen Coral Sunset peonies to plant this past week along the rocky edge of the drive. The last one was planted today and the spot marked with the small silver trellis. With luck these plants will also prove to be as deer resistant as the six Festiva maxima peonies I planted last fall. In fact, a large area next to the new drive is now mapped out for more of the Indiana state flower. Now I cannot wait for spring!

The driveway and path are now complete! It is too late in the year to do much landscaping, but I did order a dozen Coral Sunset peonies to plant this past week along the rocky edge of the drive. The last one was planted today and the spot marked with the small silver trellis. With luck these plants will also prove to be as deer resistant as the six Festiva maxima peonies I planted last fall. In fact, a large area next to the new drive is now mapped out for more of the Indiana state flower. I cannot wait for spring!