[engineerscott]

Without doing any heavy duty calculations I would suggest that we have evidence that 80W/ft^3 is a reasonable number. If we plug that in we get 32.8 kW. At 220V this would require a 150 amp circuit (which would mean 300A at 110V). Where is this oven going to be used? If it is in a residential setting then it is almost certain that you do not have a sufficient electrical service to support that kind of current. If you are in a light industrial setting you probably either have or could get a service drop that big.

Also, what are you going to use for heating elements? If you are going to use stove elements then lets assume that the element is 3 kW (a reasonable number for an average electric stove). You would need eleven 3 kW elements to get your 32.8 kW.

I think at this point you need to step back and ask yourself if you really need an oven this large. If you really have to have a oven of the size you suggest then you either have to suck it up and sign up for a 150A 220V service or you could compromise on the W/ft^3 some. As you decrease the power per cubic feet at some point you are going to be unhappy with how long it takes to heat your oven or it gets so bad that it never gets up to your operating temperature.