Lighting is one of the simplest, most reliable ways to reduce a power bill, particularly if your home still has older halogen or fluorescent fittings.
LED downlights typically use up to 80% less energy than the halogen downlights they replace, while also lasting many times longer, so the saving compounds over the life of the globe.
Rooms with multiple downlights, kitchens, living areas, and outdoor lighting left on for long periods, see the biggest impact from switching to LED, since the wattage difference is multiplied across more fittings and more hours of use.
Adding sensors or timers to outdoor and less-used areas (like a garage or hallway) can compound the saving further by cutting down on lights left on unnecessarily.
Because LED globes cost more upfront but use so much less power and last longer, most households see the switch pay for itself well within a year or two, sooner in rooms with heavy usage.