Sizing is one of the most important considerations when scheduling water heater replacement in Portland. The size of a water heater refers to its capacity and ability to meet the hot water supply needs of a home or building. Oversizing or undersizing a unit can have serious consequences. Whether installing tank-based or tankless water heaters, the Sky Heating & Air Conditioning technicians carefully determine your hot water requirements. We’ll explain how to size a water heater and its importance.
Why Is Water Heater Sizing So Important?
Water heater sizing is a core aspect of planning. When a professional who provides water heater replacement near you visits, they can assess your home and perform the necessary calculations.
Unfortunately, many homeowners request help when their water heater stops working in an emergency. They make decisions with little knowledge of the ideal storage tank size or input capacity. This can lead to prioritizing upfront savings over a unit that meets demand and lowers operating costs over time.
How Water Heaters Are Sized
Determining the right size of a water heater requires considering the following factors:
- Number of People: A 30- to 50-gallon water heater can serve a household of one or two people. However, a unit of at least 75 gallons is needed for a family of five or more.
- Peak Demand: Peak demand is measured in gallons of hot water needed during the busiest hour of use. It varies depending on the number of bathrooms and appliances in your home.
- Hot Water Devices Served: Know the faucets, showers, washing machines, dishwashers, and other appliances that may be used simultaneously, along with their flow rates in gallons per minute (GPM).
These are the specifics you need to consider when calculating water heater capacity:
- Flow Rate: Adding up the rated GPM for all devices determines the required water output, so hot water is available when you use fixtures and appliances. You can reduce flow rate requirements by installing low-flow water fixtures.
- BTU/Hour: To determine the required input capacity, add up the hot water load of all fixtures. Multiply this demand in gallons by 8.34 pounds per gallon by the degree rise by 60 minutes. This gives you the required BTU/hour rating needed.
Also, only 70% of the hot water in a storage tank is usable. Cold water mixes with hot water as it enters the tank and is too cool to use for applications that require hot water. Therefore, this is another sizing consideration.
- First-Hour Rating (FHR): Determining a water heater’s delivery capacity requires looking at how many gallons of hot water it can supply in the first hour. It largely depends on tank capacity and recovery rate. A high FHR means a water heater can provide enough hot water during peak demand.
- Flow Rate (Tankless Water Heaters): Flow rate is an important aspect of demand-type water heater performance. A tankless unit adjusts its temperature output based on water flow and incoming water temperature. Most units have a flow rate of between 2 and 5 gallons per minute.
- Temperature Rise: This is a measurement of how long it takes water to be heated to the required temperature. A water heater must accommodate a greater temperature increase if the water entering it is chillier. Consider your local climate and know the temperature of incoming water to determine the temperature rise your water heater must accommodate.
Other Water Heater Requirements
When performing water heater replacement near you, a plumber must take other considerations into account. It can impact your entire plumbing system, especially if the new model has a storage tank of a different size than the old unit. For example, the operating temperature of your entire hot water distribution system can change, which requires readjusting the maximum temperature limit stop on bathtub and shower valves. To meet code requirements, they must be set to 120℉ or less for safety reasons.
- Temperature-Actuated Mixing Valve: Installed on the unit’s outlet, it raises the temperature of stored water to increase the amount of hot water available and provide a consistent water temperature.
- Temperature Modulation (Tankless Water Heaters): Aside from flow rate, point-of-use and whole-house demand water heaters can have staged burners or heating elements for temperature modulation or a built-in flow modulating valve to slow water flow, which maintains the outlet temperature.
- Balancing Valves: Manual or automatic (thermostatic) balancing valves restrict flow to nearby branches to equalize flow throughout the system. Without them, fixtures that are farther away may see little or no water flow.
Proper water heater sizing ensures these components work correctly and that all the plumbing fixtures and water-using appliances in your home function properly.
What If a Water Heater Isn’t the Right Size?
Improper sizing during water heater replacement in Portland can have various consequences. Oversizing or undersizing the unit can lead to the following problems:
- Reduced Energy Efficiency: An oversized water heater maintains a larger volume of hot water than needed, therefore consuming more energy and increasing utility costs.
- Higher Purchase Price: Buying a larger model than necessary means you’ll pay more upfront for the water heater.
- Limited Water Flow: Having a larger tank to store more hot water isn’t a benefit when there’s reduced water flow from fixtures, which can be an issue with an oversized system.
- Not Enough Hot Water: If your water heater is too small, you could end up with a hot water shortage.
- The Unit Runs Continuously: An undersized unit can struggle to keep up with demand, so it runs non-stop and consumes more energy.
- Shorter Lifespan: Too small a water heater works harder. The increased use can accelerate wear and lead to premature failure.
- Burns: If a water heater isn’t the proper size for your home, you risk setting the temperature too high. Overheating the water increases the risk of burns and scalding injuries.
Water Heater Size vs. Fuel Type
No matter what fuel type they use, water heaters come in many sizes. Natural gas or propane models have a quicker recovery rate. Therefore, a gas-powered water heater equal in size to an electric one may deliver more hot water faster.
Water Heater Capacity vs. Physical Size
Just because you have limited space, that doesn’t mean your hot water demands can’t be met. Conventional tank water heaters are large compared to their tankless counterparts. A tankless water heater comes in many capacities. You have a constant supply and suitable flow rate yet benefit from a more compact unit that takes up little space.
Conclusion: Why Water Heater Size Is a Priority
An undersized water heater won’t keep up with your hot water demands, while an oversized unit wastes energy due to a higher standby heat loss. Therefore, you’ll pay more for electricity. The right-sized water heater delivers a balance of peak performance and energy efficiency. It may also require fewer repairs throughout its operating life and can last longer too. This reduces the cost of ownership, so you save money over time.
Call Sky for Water Heater Replacement in Portland
At Sky Heating & Air Conditioning, our plumbing professionals install tank-based and tankless water heaters in the Portland area. They’re familiar with the latest models and technologies and determine the best-sized unit for your hot water needs. Check our special offers for opportunities to save. To learn more or request help with water heater replacement or other plumbing services we offer, call (503) 673-9083 today.