I am trying to decide between a new kiln that is 9″ deep and one that is 13.5″ deep. My present kiln is 6″ deep and is a bit limiting when it comes to drapes, droprings, etc. I am not sure how often I would need the extra 4″ of height. Any advice?
9″ is very reasonable and will work for most things.
13.5″ will better accommodate large drapes/handkerchiefs and casting. Additionally, glass is less likely to thermal shock in taller kilns as the heat has more opportunity to even out on the way to the glass.
The difference in electrical cost of firing (two otherwise identical kilns) is negligible.