I can't find any place that gives a number other than for a $10c$, 8 lightyear trip being something like 68 exajoules (off the top of my head, might be wrong). I'm sure the math would tell me this if I understood it, but what I'm looking for is determining energy consumption for a given distance and "speed" from at least $0c$ to $1000c$ and how much the size of the field affects the consumption.
I'd prefer a simple equation that I can input into Google Sheets, or write a small JavaScript program so that I can mess around with the variables to use for my purposes, but I don't know if that is possible.
What I am doing is designing star ships for a sci-fi universe and part of that requires storage capacity of fuel and such, and I'd like it to be relatively accurate.