Joe, I did an overnight mash in my anvil last night, details in the light beer thread in Beer Recipes. I will post when I find out how the beer comes out.
I did an overnight mash in mine last night. Mashed in almost 14# of grain at 150F. Stirred it a few times, didn't use the recirc pump. As far as electricity usage goes, I had my Watt-a-meter hooked up to it the whole night. Before mashing in, I had it at 100% power and it was pulling 1275 watts. I turned it down to 50% power (as you did) once it reached temp. It only pulled 375 watts when the heater was on. It mashed for 8.5 hours and the total killowatt hours in the morning was .87. Last time I checked I think I was paying under $0.25/KwH so the cost of running this at night is nothing. As long as it doesn't burn the house down.
The wort was a surprise, but I guess not really when you consider the 8 hour mash. Gravity was 1.064 pre-boil and 1.073
when I transferred to the fermenter (around 6.25 gallons). That's quite a bit higher than last time I brewed this recipe. It was 1.062 when I transferred.
We'll see what happens in a week or so.