Hi Bodacious,
Here's some data that you can use to estimate your energy usage costs. The measurements are from a mod 50 but it's very close to what you'd get from a smokette. I put it on the web because it's the easiest way to go about posting it.
YMMV on several of the points here, KWH cost in particular, so make the appropriate adjustments.
Mod50 Energy UsageAll in all, I'd estimate that running your smokette at 225 F for 18 hours you'll use 9 - 10 KWH. Multiply that by your cost per KWH and you've got it.
HTH,
Joseph