The calorie count runs high, I would subtract at least 10-15% as the more accurate total.. Burning 1000 calories a hour is pretty tough unless your avg Heart rate is at 85-90% of maximum..

what is your average HR for the ride..

iPhone with SMHeartlink and Garmin GSC10 sensor and iRPM app.

wait a bit for Apple to fix their bug with OS 3.1.

prior to 3.0 OS for iPhone this worked really well for me. I can't wait for Apple to fix their OS.

the average is 83% for my typical ride.

Maybe your estimate of 10-15% lower would be accurate.

I went to REI to inquire about getting something more accurate and they assured me that the edge 305 was absolutely accurate. They said that I must have input some data about my age, weight, bike tire incorrectly.

I rechecked all the data and it seems that I input everything correctly.

I also use the sunto Heart Rate monitors and for similar rides and pacing, it comes up with much less for calories burned over the Garmin.

Err on the side of caution and just cut the Garmin calorie number in half. This will make up for the overcalculating it already does, as well as times when you coasted or took it easy. No calculator will be truly accurate unless you drop ~$1k or so for a power meter. At least by estimating on the low side you will be more likely to avoid the common pitfall of "I rode my bike today, so for lunch I can afford to eat this double cheeseburger and large fries and milkshake and a dessert."

But I do love my 305. You won't regret the purchase.

I have been using a Sigma PC14 HRM for over 3 years. Basic, dependable, inexpensive. I have a Garmin Edge 305 on the way. It will be interesting to see the comparison. I agree that the "calories burned" functions are more "ego building" than accurate!!
Cheers,
Geary