Since boiling water is my only cooking on the trail, I use one of two aluminum teakettles. I was interested to see if the larger one heats 2 cups of water faster because it has a wider base and hence a shallower layer of water. As it turns out, the difference between the 2 cup teakettle and the 4 cup teakettle is not significant. Maybe this is well known, but I thought I'd share my results.

The smaller teakettle holds 2 cups, weighs 4.8 oz, with a 4.5" dia. base. The larger teakettle holds 4 cups, weighs 6.2 oz with a 5.25" base. Both kettles flare an inch or so from the base. During the test, the outdoor air temp was 51*F and the starting water temp was 60*F. Wind varied from 0.4 to 3.8 mph. I was using an MSR Pocket Rocket with an IsoPro 8oz canister. I used an NorPro analog dial thermometer. With the stove on full, water reached 200*F in the 2 cup teakettle in 3:30 and in the 4 cup teakettle in 3:45. The fuel canister was getting low (with only 0.7 oz remaining at the end) and the wind speed was increasing. These factors could easily account for the difference in boil times. Fuel consumption and boil times were consistent with Curt Peterson's Pocket Rocket tests on Thru-Hiker (http://thru-hiker.com/articles/pocket_rocket_test.php).

So I won't carry the larger teakettle (and extra 1.4 oz) unless there are more than 2 in our party.