What Size Water Heater Do I Need?

Running out of hot water in the middle of a shower isn’t just frustrating—it can also indicate that your water heater might not be the right size. A water heater is designed to provide hot water for extended periods, but if it's too small, it won't be able to do so.  

Selecting the right-sized water heater enhances your comfort, lowers your energy bills, and finally allows you to sing that song in the shower without being interrupted by a blast of cold water. If you're wondering what size water heater you need, turn to Suntech Heat and Air. We can help you choose and install the best water heater for your household.

Why Water Heater Size Is Important

When it comes to water heaters, sizing is everything. Too small, and you won’t have sufficient hot water. Too large, you’ll end up paying for higher energy bills and ongoing costs. 

But remember that determining the right-sized water heater isn’t a guessing game. The size of your water heater depends on multiple factors in your home. That being said, traditional and tankless water heaters are measured differently. 

Tank-style water heaters, also known as ‘storage tank’ heaters, are measured in gallons, while tankless water heaters are measured in flow rate/GPM.

Factors That Determine the Right Size Water Heater

When choosing a water heater, your life and living space are important factors. For instance, someone who lives alone will have different hot water needs than a family of four.*

Below are factors to consider when determining a properly-sized water heater.

• Household Size: A larger household typically increases the demand for showers, laundry, and dishwashing. 
• Number of Bathrooms: Multiple bathrooms can lead to simultaneous hot water usage, especially during peak times. 
• Peak Usage: Consider when your household showers most frequently—do you have more morning or evening showers? 
• Hot Water Appliances: Consider appliances such as dishwashers, washing machines, and hot tubs, and how often they are used. 
• Water Usage Habits: Long showers, frequent laundry cycles, or using low-flow fixtures can significantly impact hot water demand.

*Example: If you have a family of four with two bathrooms, you’ll likely need a 50-gallon traditional water heater or a 7 GPM tankless water heater.

Sizing Guidelines for Tank Water Heaters

Traditional tank heaters are designed to store, heat, and distribute hot water. The tank must be refilled and reheated once the hot water is gone. 

Below is a general guideline for the appropriate tank size, based on the number of people in your household.

The size of a traditional storage-tank water heater is determined by its first-hour rating (FHR), which indicates how many gallons of hot water the heater can supply during peak hours. 

If you have a growing family, are adding another bathroom, or just need assistance in choosing the right size, call Suntech for a personalized assessment.

Sizing Guidelines for Tankless Water Heaters

Tankless water heaters differ from traditional units in that they do not store water. Instead, they heat water as needed. Their performance is measured by flow rate (gallons per minute, or GPM) and temperature rise.

The maximum flow rate is determined by the number of fixtures being used simultaneously and the flow rate of each fixture. The temperature rise is the difference between the water heater's set temperature and the building supply's inlet temperature. The colder the incoming water, the harder the system has to work.

Below is a list of common fixtures and their flow rates.

For example, if two people shower while someone starts laundry, the tankless system needs ~6.5 GPM. We know this information can be confusing, which is why our team can help you choose the best tankless water heater for your specific needs.

Other Factors to Consider When Choosing a Water Heater

Don’t rely on your household size and peak water usage to determine the best water heater. Keep these considerations in mind when choosing a water heater.

• Fuel Type: Gas can reheat faster and affect tankless sizing, whereas electric heaters may have a lower upfront cost but slower recovery.
• Efficiency Ratings (EF or UEF): A higher efficiency rating means lower operating costs. Electric water heaters are typically more energy efficient. 
• Available Space: A larger, traditional water heater is ideal for homes with plenty of space. A tankless water heater may be the better option if space is an issue.
• Water Quality: Areas affected by hard water, such as in Oklahoma City, may affect maintenance needs or size choice
• Budget: A traditional water heater is more budget-friendly than a tankless unit. However, tankless water heaters may save money in the long term.

Suntech Heat and Air can walk you through the water heater buying process. We’ll guide you every step of the way.

When Should You Upgrade or Replace Your Water Heater?

If you have an old water heater, you’re probably wondering whether to repair or replace it. You might also be experiencing issues that would warrant a premature replacement. 

Use these identifiers to determine whether you need to upgrade or replace your water heater. The best part is that Suntech can help you make a decision.

• The water heater is 10–15+ years old
• There are frequent hot water shortages
• Your monthly energy bill is rising
• You notice rusty or discolored hot water
• You hear unusual noises (rumbling, popping)
• You see visible leaks or corrosion

If your current water heater fails to keep up, increasing the size or switching to a tankless unit could help.

Let Suntech Help You Choose the Right Water Heater

Choosing the right water heater doesn’t have to be a headache—simply call Suntech.

Our team offers expert recommendations based on your household size and water usage. And don’t worry, we always factor in your budget needs. We proudly handle water heater installation, replacement, and regular maintenance for homes and businesses in the Oklahoma City area. 

Contact us for a free consultation or use our quick online form to request a service.

Get a Free Estimate

Frequently Asked Questions

What happens if my water heater is too small?

If your water heater is too small, you may frequently run out of hot water, and the unit will wear out faster.

Is a bigger water heater always better?

A larger water heater than necessary can waste energy and increase utility bills.

How is tankless water heater size determined?

The size of a tankless water heater is based on gallons per minute (GPM) and the amount of hot water your household uses at once. 

Can I replace my tank water heater with a tankless one?

Yes, you may need additional plumbing services or electrical upgrades. If you’re interested in switching to a tankless water heater, contact a professional.

Does the Oklahoma climate affect water heater performance?

Yes, this is particularly true for tankless water heaters. Cold weather forces a water heater to work harder.