When choosing the best electric or gas water heater, capacity is one of the design considerations you'll want to pay close attention to. Choosing a water heater with the capacity to meet your needs will save energy and money in the long run. When it comes time to replace your water heater, only purchase the authorized Rheem gas water heater parts. Additionally good are an Energy Star certification and an excellent guarantee. Energy Star-certified water heaters are up to 10% more efficient than non-certified models, meaning you’ll be able to save even more on your monthly energy bill.