One week update

It has been a week since they filled up the tank. Time to compare and estimate how fast we're using oil.

According to wunderground.com, there were 159 heating degree days for that week. A day's heating degree days is how much below 65F (a fairly arbitrary number meant to approximate room temperature) the day's average temperature was. The people at wunderground rather disappointingly compute the day's average temperature using just the daily high and low, rather than hourly or more frequent measurements. For instance, imagine that it's a nice warm 50-degree day - this time of year, that is warm - until 10pm when a cold front comes in and the temperature drops to 30 degrees. By their formula the average will be 40, when it was clearly much closer to 50.

On the plus side, the tank indicator hardly moved from last week. On the minus side, it's hard to calculate how much it moved and thus how much oil we actually used. I'd like to calculate how much oil we use per degree-day (possibly adjusted for the fact that we keep our place colder than 65, so perhaps we should use a lower temperature as our baseline), which will let me use historical degree-day data to project our total gallons of usage for the entire heating season. More to come after I've stared at the pictures side-by-side.