Just do everything possible to get your energy costs down. CFLs in every socket, consider installing light timers, high efficiency appliances (or is this just a grow house, with no people really using it for living essentials?). 4k worth of lights is getting to a pretty big draw but I've heard of people running lots more than that and never having problems. If you have the money, consider getting solar panels installed I'm sure that'd take quite a chunk out of the bill in the sub tropics.