Originally Posted by
gregf83
Rule of thumb is normally Cals = 3.6 * Avg Power. For your example at 276W you'd expect to burn about 994Cals. If you use Joules you need to multiply by about 4 to account for efficiency.
Rule of thumb is 1 kJ = 1 calorie. 276 average watts = 1 mJ an hour.
1 mJ an hour = 1,000 calories.
Zero reason to make it any more complicated than that. 6 calories = 1.5 grams of sugar. Not consequential in the least.