Renewable energy is energy that is collected from renewable resources that are naturally replenished. It includes sources such as sunlight, wind, rain, tides, waves, and geothermal heat.
Energy efficiency is the practice of using less energy to provide the same amount of useful output from a service such as heating water, lighting, or cooling a fridge.  The improvements include higher efficiency HVAC systems, sealing air ducts, increasing insulation in walls and attics, using smart thermostats, and sealing windows and doors.