LED Lighting for all purposes - street lights, office buildings, warehouses, etc., directly saves 50%-80% of energy used on lighting, which can represent 15% of total energy use. Payback is 1.5-3.5 years with a 10-20 year asset life so after the first few years of energy-saving, beyond that it's all gravy! This is THE most direct way of "low-hanging fruit" to save energy and money.