Need a new hot water heater? Wondering what size to buy? Today you'll learn that some are too big, others are too small, and never does ?one size fit all?! Here are a few tips that will help you decide. While the term ?capacity? refers to size, in reality, you must consider two things with regards to capacity: storage and recovery time (how quickly it can re-heat a tank of water.) Common capacity sizes range from 40 to 75 gallons, and electric takes longer than gas to reheat a tank. With that in mind, here are a few rules of thumb: for a one-bath home, 30 to 40 gallons is okay (either gas or electric). For one-and-a-half baths, 40 gallons is the minimum. For two to three baths, use a 50-gallon gas or 60 to 80 gallon electric (due to longer reheating). For large homes with four baths or whirlpool tubs, use a 75-gallon gas tank or 120-gallon electric unit. Get the right size for your house and family and you won't be taking cold showers any more!