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Making sure you have enough hot water for your showers, laundry, and dishes is critical when choosing the right water heater replacement for your home.
Choosing the size of your unit depends on several factors, including household hot-water demand, simultaneous fixture use, fuel type, and whether you want a standard or tankless water heater.
At Apex Pros Plumbing, Electrical, Heating and Air, our team of professional plumbers can help you with water heater sizing to ensure you have easy and reliable access to the hot water you need.
Why Does Water Heater Sizing Matter?
Successful water heater installation requires a properly sized system, as proper sizing affects comfort, energy use, operating costs, and equipment performance. With water heaters, bigger isn’t always better, and correct sizing helps homeowners avoid paying for unnecessary capacity.
The most common sizing issues homeowners face include:
- An undersized unit that struggles during showers, laundry, and dishwashing.
- An oversized tank that wastes energy by maintaining more hot water than the household needs.
- An undersized tankless model that may not provide the required temperature when several fixtures run simultaneously.
Homeowners should also avoid simply replacing their water heater with one of the same size. Because household demands change and water heater technology has improved, homeowners should reassess their water heater size when choosing a new system.
How Do You Calculate Your Home’s Hot-Water Demand?
When measuring your home’s hot-water demand, identify the busiest hour of hot-water use. This is often in the evenings, when the dishes are running, the laundry is going, and family members are showering.
During this peak time, estimate how many showers, sinks, and appliances are operating simultaneously. Then consider:
- Number of household members
- Number and duration of showers
- Bathtub size and frequency of use
- Dishwasher and washing-machine use
- Number of hot-water fixtures operating simultaneously
- Changes such as a growing family, bathroom addition, or new appliances
For example, a small family may use two showers and a dishwasher during their peak morning hot-water use, but may also plan to have another child soon or install a soaker tub.
Providing this general assessment to a plumber can help them create a more accurate demand estimate, ensuring you install the right size water heater.
What Size Standard Water Heater Do You Need?
When selecting a standard water heater, homeowners should pay close attention to two ratings:
Tank Capacity
Tank capacity is the number of gallons of hot water a water heater can store. While many manufacturers use household size to provide preliminary estimates on the right tank size, homeowners should use water usage habits as the final determining factor. Remember, for water heater replacement, there isn’t a one-size-fits-all gallon recommendation.
First-Hour Rating
First-hour rating is the amount of hot water a fully heated tank can deliver during one hour, including water reheated during that period. At Apex Pros, we recommend finding a system with a first-hour rating that matches your household’s peak hourly demand. This is generally more useful than looking at tank capacity alone when comparing models.
What Size Tankless Water Heater Do You Need?
Tankless water heater sizing is a bit different from that of a standard tank system, as there is no storage capacity. Instead, homeowners can rely on these two measurements:
Required Flow Rate
Finding your required flow rate involves adding the gallons-per-minute ratings for the fixtures and appliances they expect to operate simultaneously. This is because two showers and a dishwasher running at the same time will require a higher flow rate than operating a single shower.
Required Temperature Rise
Tankless systems also measure temperature rise. This is the difference between incoming groundwater temperature and the desired hot-water temperature. In Ohio, cold incoming water requires your water heater to produce a greater temperature increase, which can reduce its available flow rate. Comparing manufacturer performance data at the requirement temperature rise can be the best way to find the right system for your home.
What Else Should You Consider Before Water Heater Replacement?
Other factors that may impact your final choice include:
- Gas or electric fuel availability
- Energy-efficiency ratings and expected operating costs
- Available installation space
- Venting, gas-line, electrical, and plumbing requirements
- Upfront installation cost
- Upcoming home renovations or additions
- Local code and permit requirements
Homeowners will also need to remember that switching from a standard water heater to a tankless model may also require utility or venting modifications, making a professional site evaluation important.
Schedule Water Heater Installation With Apex Pros
When finding the best system for your water heater installation, always consider sizing. Tank models should be selected based on peak hourly demand and first-hour rating, whereas tankless units require calculations of simultaneous flow rate and temperature rise.
At Apex Pros, our team is here to help you make this complicated choice hassle-free.
Contact Apex Pros today for professional water heater sizing in Columbus or Dayton, OH.
