When choosing a hot water heater, you’ll need to consider what size (capacity) water heater you will need before you determine anything else. After you know what size you need, you can look into what each type of water heater will cost you to install and to run (energy costs over time). Once you’ve taken these factors into consideration, you’ll be ready to choose a new water heater.
This article addresses how to choose the right size hot water heater for your home.
Choosing The Right Size Water Heater For Your Household
Many people think they have to size a water heater by the size of their house, but really, this isn’t what’s important. What matters is how many people live in your household and how high the peak hot water demand is at your busiest hot water usage time of the day. It also matters if you’re sizing a tankless or traditional tank water heater.
First, Determine What Your Peak Hot Water Demand Time Is
Is it at 7:00 a.m., when all five of your family members are taking showers at the same time? Is it at 8 p.m., when you are running baths for all three kids plus the dishwasher and the washing machine?
To Size A Traditional Tank Water Heater
You’ll need to tally up the amount of hot water you need available during the hour of peak hot water usage each day. You can do this by adding up averages from a chart like this one (which gives average gallons of hot water used per one time usage for activity associated with appliance or faucet):
Water used in shower – 12 gallons per one-time use
Water used for one load of laundry – 32 gallons per one-time use
Water used for bath – 9 gallons per one-time use
Water used for sink – 4 gallons per one-time use
Water used for dishwasher – 14 gallons per one-time use
You’ll want to add up how many of these activities are performed during that peak hour of hot water usage to figure out how much hot water you need available at one time. Once you’ve got this number, you’ll know you need a hot water tank that can heat at least this much water at one time.
To Size A Tankless Hot Water Heater…
You’ll need to add up home many gallons per minute of hot water you need for your tankless water heater to produce at your peak hot water usage times. This will require calculating the flow rates of different faucets and showerheads to determine how much hot water you need available during those peak times.
Tankless hot water heaters have to heat the water on demand, so you’ll need to also factor in what temperature your water is before heating (usually about 50 degrees F) so you can determine what the temperature rise is (how much the water need to heat up) for the task required.
Your water is probably starting at 50 degrees and being heated (for most uses) to 120 degrees, although you’ll need to heat it to 140 degrees for the dishwasher. That means you need a temperature rise of 70 degrees for most tasks, but a temperature rise of 90 degrees for washing dishes.
Most gas-powered tankless water heaters can produce a flow rate of 5 gallons of hot water per minute (at a 70 degree temperature rise). Most electric-powered tankless water heaters can produce a flow rate of 2 gallons of hot water per minute (at the same temperature rise of 70 degrees).
Let Us Do The Math For You
Here at ER Plumbing, we’re water heater experts. We can quickly calculate out what size (capacity) water heater you need and what type of water heater will be most cost-efficient for your home. We’ll explain the different options so you know exactly what you’re getting. Then we’ll install the heater for you, so you’ll know you’re getting the right water heater, at the right price, installed by experts. If you ever have problems with your water heater, we’ll be available 24/7, year round, to set things right.
Contact us today for an estimate on a new water heater.
