Sizing is one of the most vital considerations when buying a new water heater. The new appliance must accommodate all your household’s hot water needs. If it is the wrong size, you’ll run out of hot water too soon and may have to wait for a tank to refill and for the water to heat to the appropriate temperature. Continue reading to find out how to calculate the correct water heater size.
How to Calculate the Correct Water Heater Size
Start With Household Size
A tanked water heater uses a tank to store hot water when needed. Consider your household size when buying a tanked water heater. For example, a two-person household needs a 30-gallon water heater to accommodate showering, washing clothes, washing dishes, cooking, and other cleaning requirements.
The rule of thumb is to add 10 gallons per household member. Three people would need at least a 40-gallon water heater, and up to four would require a 50-gallon model. If five or more people are living in your home, you should consider a 75-gallon water heater.
How Many Bathrooms Do You Have?
Consider that your family may use more than one bathroom simultaneously. Add at least 3.5 gallons per bathroom to your water heater size. The location of your bathrooms may affect how quickly the water heater produces hot water and how long it takes to reach each shower.
If you have a two-story home, you may need more than one water heater, or you may consider installing two tankless water heaters to reduce water consumption. A large family with multiple bathrooms on different floors may save by using an on-demand model strategically installed near each bathroom. Our plumbers at Benjamin Franklin Plumbing can help you calculate hot water consumption based on these factors.
Check the First-Hour Rating for the Water Heater
Every water heater model provides a first-hour rating indicating how much hot water it produces within one hour. The water heater’s hourly heating capacity determines the appropriate tank size. Start with activities that occur during the time your family uses the most hot water.
Showering takes about three gallons per minute, so if you take a 10-minute shower, you’ll use 30 gallons of hot water. However, shampooing your hair could require five gallons; adding this to your 10-minute shower, you’ll use about 35 gallons of hot water during one shower.
Shaving requires at least two gallons of hot water, bringing this total to 37 gallons of hot water. Consider this calculation for each person in your household. Determine the water heater size according to the highest amount of hot water your family uses and when. If the water heater produces 40 gallons of hot water within one hour, it accommodates one person’s hot water needs for one hour only.
You’ll use one or two gallons of hot water each time you wash your hands. Basic food prep may require up to six gallons. Mopping, cleaning countertops, and hand washing pots and pans can require up to 16 gallons of hot water. You’ll use up to ten gallons per load if you have a dishwasher. Consider these calculations when comparing water heaters and their water heating capacity within one hour.
Calculate the total peak hour demand for showering and cleaning demands when you use the most hot water. For example, you need a tanked water heater that produces 80 gallons per hour if two people simultaneously take a 10-minute shower in the morning. If you have a smaller tank, someone may have to wait for the water heater to recover and produce more hot water.
Consider a Tankless Model
Tankless water heaters produce up to five gallons of hot water per minute. On-demand water heaters are convenient and don’t require you to wait until the tank fills and heats the water. The water heater heats the water whenever you turn on the hot water.
A large family using high volumes of hot water needs a water heater that meets their total peak hour demands. Calculate how many gallons each person uses for showering. Consider if more than one shower is used at the same time. Tankless water heaters using electricity will produce less than a gas model. Consider this when choosing a tankless water heater.
How quickly you need hot water and the total number of showers indicates the hourly capacity your family needs. These factors may also determine if more than one tankless water heater is necessary to accommodate your household’s hot water demands.
Choosing the correct water heater size ensures your family has enough hot water when needed. Your household size and total peak hour demands help you calculate the tank size required for your home.
The first-hour rating determines how much hot water the water heater produces within one hour. These calculations could also help you choose the water heater type that is best for your family. Call our plumbers at Benjamin Franklin Plumbing for assistance selecting the best water heater.