As I tried to lay out in an earlier posting, much depends on what you want to compare: fuel burn per trip of fuel burn per passenger.
The official documents provided by the manufacturers
can provide some answers, as they give us numbers like empty weights, fuel capacities and also range-payload diagrams.
So let's compare the B737-800 and the A320-200 with a similar takeoff weight. I choose the 170 klbf/77.1t MTOW variant of the B737-800 and the 169,756lbf/77t variant of the A320-200 (WV010).
On page 3 and 4 of section 3-2-1 of the Airbus document you can see the payload range diagram of the A320-200 with CFM56-5B and V2500-A5 engines respectively. For a payload of 30,750lbs (205lbs per passenger you get a maximum range of 3,050nm.
To calculate the fuel burned for these two (virtual) missions, we need the "Zero Fuel Weight" (Operational Empty Weight + Payload) and subtract that from the MTOW.
Payload was 30.0750lbf for both aircraft.
Operational Empty Weight (OEW) is
- 90,027lbf for the A320-200 and
- 91,300lbf for the B737-800
Yes, contrary to what many people think, the A320-200 - meanwhile - is lighter than the B737-800; although that may be different from operator to operator and on a per-seat basis the B737-800 should be lighter anyway.
Thus the "Zero Fuel Weight" is
- 120,777lbf for the A320-200
- 122,050lbf for the B737-800
Fuel hold and fuel burn (minus reserves) thus is
- 48,079lbf for the A320-200
- 47,950lbf for the B737-800
Fuel burn per nautical mile flown then is
- 15.76lbf for the A320-200
- 15.98lbf for the B737-800
Thus the B737-800 burns 1.4% more to carry the same payload.
What puzzles me a little bit is that Airbus states a cruise speed of Mn0.76, whereas Boeing just states "at LRC". This could be anything between 0.76 and 0.78. If LRC means something higher than the Mn0.76, we would have to correct the range and therefore the fuel burn per nautical mile of the A320-200, so that range will fall and fuel burn would raise.
But - bottom line: for a typical mission of 500-800nm, where cruise speed does not play a big role - neither for trip time nor for fuel burn - the A320-200 and the B737-800 are very close in fuel burn for the same payload.
If one uses the higher passenger capacity of the B737-800, thus transporting more payload, the fuel burn will go up slightly. Fuel burn per trip would be above the A320-200 number then.
Boeing's claim, that the B737-800 would be 8% better can not be backed by this little analysis and was always disputed by Airbus. As Scott Hamilton pointed out recently, airline fleet managers also seem to back Airbus here.
And as the fuel burn improvement for the B737RE is seen by about 10% compared to the 15% of the A320neo, the gap on a per-seat basis between the A320neo and the B737-800RE should narrow, if not close. On a per-trip basis, the A320neo should have an edge anyway. This is particular true for noise sensitive airports where noise fees are factored in the landing charges. The smaller fan diameter of the B737RE will result in higher noise levels than the fuel burn and noise optimized engines on the A320neo.
Update Aug19, 2011:
I would like to comment on some comments made:
Of course the airport planning manuals are not too accurate and I did not intent to claim that I made a detailed and fully accurate analysis. But suggested that both documents have a similar level of accuracy, the conclusions should be not too far off from reality.
The Boeing document is for the non-winglet version of the B737-800, this is right. But for typical (short)missions the effects of winglets on fuel burn are not that big. And with the introduction of the "sharklets" the two aircraft would be on-par again.
The claim that the 737-800 flies missions the A320 cannot (range-wise) is contradicted by flyhigh@tom ina thread over at airliners.net. I cannot comment on that myself...
Another post from seabosdca states some issues:
1) I already commented on the winglets.
2) I compared a mission with the same paylaod with about the same MTOW to get a feeling about the fuelburn per mile. Fuelburn per mile would not change significantly if I would choose the 79t MTOW version of the 737-800. In fact, it could even go higher as the aircraft has to lift more weight at the beginning. I once made a study and it showed that aircraft as different as the A380-800 and the B787-8 which are both designed for 7000-8000nm have the lowest fuelburn per mile when flown at ranges like 4000nm.
3) The mission I "flew" was the longest mission possible with that particular payload and MTOW, as the payload-range-diagram shows. The reason why I choose same MTOW's I laid out before. Normally, if you are an airline manager, you compare the same mission (same stage length) to compare fuel burn for different aircraft and you get the fuel burn for this particular mission from the aircraft OEM. As I did not have fuel burn numbers for any mission I choose to compare the fuel burn from reading the payload-range diagram. And to have missions with similar ranges I choose similar MTOW's.