There has been a lot of talk on the motionbased forums about how the calorie counter in the Edge 305 is not accurate. So I did a bit of searching and found an article on how to predict energy expenditure based on heart rate. I considered writing a program to "correct" the calorie expenditure in Training Center (the software that came with the Edge) but ended up getting bored with the project before I finished it.
However I decided I wanted to lose some weight in hopes that it would help me with my hill climbs. So I started counting calories that I am eating each day. The calorie counting has worked good at helping me lose the 10 pounds I figured I could lose. Now I just need to work at maintaining my new weight. Anyway this got me interested enough in the Edge calorie problem enough to put together a little calorie calculator in my blog. So I have added it to the left panel for anyone that cares. Given the number of minutes exercised, the average heart rate it gives a calculated calorie expenditure.
If you know your VO2max you can improve the calculation. Using the VO2max value you could also adjust the formula based on your fitness level. I'm no expert on VO2max but for a lower fitness level use a lower VO2max (50's?), for a higher fitness level a higher VO2max (60's?).
So for what it is worth here it is. http://www.epicbiking.com/calories.jsp