Check your ducts for air leaks. First look for sections that should be joined but have separated and then look for obvious holes. Consult with a professional about repairing duct leaks. Safe duct repairs require a licensed heating, ventilating, and air-conditioning contractor.
Use task lighting; instead of brightly lighting an entire room, focus the light where you need it. For example, use fluorescent under-cabinet lighting for kitchen sinks and countertops under cabinets.