At Boise Friends Church we did a lighting retrofit where we changed out old 400 watt metal halide lights in church gym to a 6 lamp T8 highbay. This resulted in increased light levels, and reduction in energy of over 50%. The old metal halide lights also took several minutes to come up to full power, where the T8 fluorescent lights come on instantly.
Besides the gymnasium lighting upgrades, we also changed out over 100 incandescent 60 watt bulbs to 11 watt LEDs. The 11 watt LEDs are a dramatic decreased in wattage, and will last 10 times longer than the old incandescent bulbs.