kstills wrote:

That calc for #2 doesn't seem to work out...

Well, lets see for both of them, using an example of a median temperature of 15 degrees F. for the day:

For electricity at 100% efficiency:

3.45 x (65-15) = 172.5 KWH

172,5 KWH x 3,412 BTU's/KWH = 588,570 BTU's (which equals 24,524 BTU's per hour for 24 hours)

For oil at 80% efficiency:

0.11 x (65-15) = 5.5 gallons

5.5 gallons x 138,600 BTU's/gal. x 0.80 = 609,840 BTU's (which equals 25,410 BTU's per hour for 24 hours)

OK, to make things a bit more even lets call it:

Gallons of #2 Heating Oil per day = 0.10616 x HDD's

And if (for example) the whole month of January averaged a very realistic (for this area) 20 degrees F:

31 x (65-20) x 0.10616 = 148 gallons of # 2 heating oil required for the month (at 80% efficiency)

But remember, my chosen factors of 3.45 KWH (electricity) and 0.10616 Gal. (oil) and 1.55 Lbs, (coal) are for my home only. Your home will likely be different. Also remember that there are a lot of oil boilers and furnaces out there that are older and may only be operating in the 60% to 70% efficiency range.