Thanks for the info Craig, the Acunto ovens look very well insulated. That makes me wonder which branch of the Acunto family supplied the first oven for Una Pizza Napoletana when they were in New York because I've read comments from them that the SF oven used much less wood, which has my wheels spinning.
I don't think it is the same as mine - it doesn't look anything like it. I don't think the oven in UPN/Motorino was built on site. I seem to remember him talking about being worried that it wouldn't fit through the fron of the restaurant, but maybe I'm confusing it with someplace else?
As for wood usage, I'm sure there are plenty of factors, but insulation intuitively would be near the top of the list. The more easily the heat escapes, the more fuel you need to replace the lost heat and keep the oven hot. It’s pretty basic physics.
I think the physical size of the wood burned (the cross-section in particular) is the other important factor. For the same mass of wood, a larger log burns slower and longer than several smaller ones (less oxygen in contact with the fuel in a larger log). Generally speaking, the same amount of energy is released either way, but it is released over a longer period of time when burning a larger log.
Here is my theory on wood consumption, keeping in mind that I want an open flame when I bake. If I didn’t, insulation might be even more of a factor. For me, I always have to have a fire burning which means I’m consuming fuel when I might not need to be if I was only concerned with maintain the operating temperature:
I think insulation is the most important factor. The better the insulation, the less energy you need in a given amount of time to keep the oven warm. If your oven is well insulated, once you get it up to temperature, you can burn larger logs for the open flame (and replacement heat) during the bake. This works in a well-insulated oven because you don’t need as much replacement heat to keep the oven at operating temperatures. If you used smaller logs for the open flame, you would burn more fuel simply because they burn faster.
Let’s say you have a less well insulated oven of the same size, once you get it up to operating temperatures, you will either need to burn smaller logs which burn and release their energy faster or several larger logs simultaneously to replace the heat lost and keep the oven at operating temperature.