A local printing company that we frequently work for had metal halide lighting. This type of lighting was the best at the time to install, but it uses a lot of power, take a while warming up to full brightness and if the lights are turned off for any reason they take a further 10 minuets to come back on.
The lights in the warehouse were 400 watt, and we replaced these with 200 watt LED lowbay lights. These have a crisp white light that when measured gave out 80% more light(as you can see from the before and after photo above). These also have an instant on, with no warm up or cool down time. They come with a 5 year guarantee and an expected 50000 hour life(this should give around 19 years of 10 hour days).
We also replaced the lights along the storage area with 140 watt leds, again brighter and perfectly adequate for the situation.
In summary we dropped the power consumption by 58% and the yearly running costs by £1346 per year. this giving a payback 2.4 years and increasing the light levels by 80%