On average, around 1200-1300 gallons of fuel oil without the stove. That'd be anywhere from $4,848.00 - $5,252.00 at the current rate of $4.04 a gallon I had to pay a few weeks ago to top off my tank (which I still use for hot water and suppmentary heat). With the coal stove, my annual oil consumption is dropped to roughly 400 gallons (depending on just how cold it gets in the winter). Thus this "saves" me anywhere from $3,232.00 - $3,636.00 a year. However, of course, I have to pay for coal...which in VT isn't as cheap as NE PA. I pay anywhere from $330-$350 a ton (typically $7 a bag for 40# bags so let's say $350). I burned 4,120 lbs of coal last year and I'm on pace for around that this year (my stove was down for 2 weeks in Dec so despite the cold, I'll likely end up around the same this year)...So, at $7 a bag, that's 103 bags for a total of $721.00. So figure on $1,616.00 for the oil and $721.00 for the coal for a grand total of $2,337.00 or a savings of around $2,915.00 on the high end and a low-end estimate of $2,511.00.
I installed the stove and entire chimney system 3 winters ago for roughly $3200 and have had to pay about $200 in maintenance parts (new fire bricks and a new baffle plate this year) and change but with that savings, I'm so far about $4-5K ahead of the game since I went to coal full time.
Another key point...the price of fuel oil has been all over the board in the past 3-4 years for me...its been anywhere from $3.25 a gallon to $4.50ish a gallon with no predictability whatsoever. Coal hasn't budged...the same dealer that charged $7 a bag or $330 a ton for bulk orders is still charging $7 a bag or $330 a ton for bulk.
Math is fun.