Some of you may be interested in this.

www.degreedays.net

I just got an oil delivery and wanted to calculate the real difference in
efficiency of my old versus new boiler. I use the mentioned web site to get
the information I needed from a nearby weather station. This is the way the
oil companies figure the automatic delivery for you.

My savings over the past 10 months has been 40%. A real savings of 248
gallons. The new boiler is paying for itself in oil cost.