Maybe $0.15 per kW/hr is typical rate, which is 4.5 cents per hour, or $1.08 per day, which works out to about $33 / month and $400 / year.
Not everyone will be comfortable with that, but of course if you can afford the big Krells, you probably won't bat an eye.
Not everyone will be comfortable with that, but of course if you can afford the big Krells, you probably won't bat an eye.