Marine fish tank lights costing a fortune.?

i have been running my 4 foot marine tank with a double halide light for the last year and my electric bill has shot up.i now realize that it is the lights that are costing so much to run.is there an Alternative light that i can buy that will keep my corals alive and at the same time not cost so much to run.i have tried t5 tube lighting in the past with not much success.any help would be much appreciated