Hard data based on my experience and testing.
1)I have recorded my fuel usage on ski trips dating back numerous years. All WG. Basic numbers are that for one person, melting snow at both breakfast and dinner (i.e., finding no running water) I average 85 gms or 3 oz. (by weight) of fuel per day. For two people same situation, I average 124 gms of fuel per day.
2) to compare stoves I ran a test where I primed the stove (if needed) and brought 12 cups of water to a boil (from 50degree starting water) in a 4 liter pot. MSR Simmerlite and Whisperlight both averaged 43 gms to do this: my Coleman F1 Ultralight used 34 gms of fuel. What makes this test particularly germane is that the amount of WG burned is almost exactly half of what I use per day solo, thus this accurately recreates the single burn I make in the morning or evening and thus the ratio of prime to burn is accurate.
3) I carry the smallest Sigg bottle with the pump in it(5 oz empty of fuel but with pump) and full of WG, then additional fuel is in PET bottles (I choose relatively thick and stout bottles to be on the safe side and have never experienced a leak).
4) So for an 8 day trip solo, my weight of WG and containers is 24+5+1.5=30.5 oz. that's 24 oz. of fuel, 5 oz for sigg bottle with pump, and 1.5 o for 500ml plastic bottle.
5) Same trip canister:544 gms of fuel, so one 450 and one 110 gm canister, or 23.5+7=30.5 oz
Thus the weight of fuel and containers is the same. And since the weight of the pump in my case is included in the fuel container weight, the simmerlite stove weight – 6.35 oz. – can be directly compared to a remote canister stove weight. so with a Caffin you are ahead by about 3 oz; with a Kovea Spider (which is about the lightest commercially made remote) you are ahead by less than half an ounce.
6) For an 8-day trip with two people, the WG starts to pull ahead. I'd need 36.4 oz of WG, so I'd have 44.5 oz of fuel and container with WG, and I'd need 816 gms of canister gas, or 47 oz with containers (2, 450gm cans). Around 10 days with 2 people you'd offset the weight savings of the Caffin.
But you'd never get very far ahead because you're still dealing with the fact that you burn more WG than you do canister gas. The WG only stays ahead because you can carry it in such light containers. And at particular numbers of days it could swing the other way if the canister gas needs come in right at a quantity that matches the canister sizes while the WG just goes tips over to an additional plastic bottle – it's that close.
Final caveats:
a) This is based on one burn each meal – I light the stove once in the morning and once at night. If you prime more often that that you will lose ground.
b) The canister stove used for comparison is an upright, and testing published here on BPL (and done by the man himself) showed uprights having better fuel efficiency than remotes. But whether that is due to burner styles, and might not apply to the Caffin which is an upright burner fed remotely, is an unanswered question. the only upright canister stove I own is suspect (Bulin B-5) and thus I did not rely on the numbers I got when testing it – it used just as much fuel by weight as the WG stoves.
My final take was that for me it's so close that it doesn't matter, and thus not worth buying a new stove.
It's worth noting that the MSR stoves do not have the reputation for fuel efficiency that the venerable Svea 123R has. But I don't have numbers for a Svea so I can't compare accurately.
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