Omnia Mechanical Group

571 Timpson Place Bronx, NY 10455

Phone: 212-534-2500

Contact us on email!

What Size of Water Heater Do I Need for my Multifamily Building?

Landlords must ensure all tenants can access hot water 24 hours a day. In some older properties, especially those retrofitted into apartments or multi-family properties, the existing hot water system may not be adequate. To ensure continuity in the hot water supply, you, as the landlord or property owner, are responsible for upgrading the system. That can bring up questions like what size water heater do I need?

Determining the size of a water heater is no simple task; you must know the ins and outs of your building, tenant habits, and specifics about your existing water supply. Discover the factors that contribute to water heater selection and installation.

What Size Water Heater Do I Need? 6 Factors To Consider

1. Number of Units

The number of units in a building is the most significant factor to consider. Typically, the more units your property has, the more people it can house or accommodate. As the population in your building increases, so does hot water usage.

Besides the number of units, you also need to factor in the size of the units. Larger apartments usually have more fixtures and possibly multiple bathrooms. Also, depending on the property, the apartment or unit may have in-unit laundry. These extras can lead to increased hot water demands, which calls for a larger water heater or multiple water heaters.

2. Number of Bedrooms Per Unit

The number of bedrooms in a building is generally a better indicator of occupancy than the number of units alone. For example, a one-bedroom apartment typically has fewer residents than a two-bedroom apartment.

More people living in a unit equals more hot water usage. A one-bedroom unit typically can house two people comfortably. Each of those people needs to bathe and wash dishes and clothing. A two-bedroom unit doubles the possible occupancy and increases the hot water demands in the unit.

3. Fixture Flow Rates

Kitchen faucets, bathroom showerheads, and laundry room washers all have specified flow rates. The flow rate refers to the water volume a fixture delivers over a set period, usually expressed as gallons per minute.

Note the difference between water volume and pressure. Water pressure explains the force of the water coming out of a faucet. Water volume refers to the measurable amount of water coming out of the faucet.

Tankless water heaters use the same GPM metrics as fixtures, but tank heaters do not. Figuring out water heater size based on fixture flow rates is challenging because the number of fixtures the building has multiplied by the number of units and the possible simultaneous use of the fixtures is a complex equation. Calray Boiler can help you figure out what size water heater you need without giving you a migraine in the process.

4. Peak Demand

Peak demand refers to the highest usage periods. Rather than the daily usage average, these are the times of day when hot water demands surge. Your systems are most vulnerable to supply shortages during peak usage periods.

For hot water, peak demands usually occur in the mornings and evenings, typically corresponding with people getting ready for work or having dinner and getting ready for bed. Knowing specific peak times and the average uses for those times can help you select an appropriate-sized water heater.

Some property owners think it is best to overcompensate and buy a larger water heater than they need. While such a purchase will eliminate any worry over hot water shortages, it also means your property wastes energy and costs you money. You want to find the Goldilocks tank, the one that is not too big or too small but just right.

5. Incoming Water Temperature

When deciding what size water heater you need, focusing on water output or storage is easy. While output matters, you cannot overlook the importance of incoming water temperatures, especially in NYC, with its cold winters.

A water heater has to raise the temperature of incoming water to a desirable temperature, usually around 120°F. The difference between the incoming temperature and the desired temperature determines how hard your water heater must work.

Regarding incoming water temperature and tank size, there are advantages and disadvantages to purchasing a larger or smaller tank. Calray Boilers can help you weigh the pros and cons to find the perfect solution for your property.

6. Water Heater Type

What size water heater you need also depends on the type of water heater you purchase. A storage tank water heater is usually the largest option. The system holds a reserve of water that is preheated so it is ready for demand. These units typically specify a first-hour rate, indicating how many gallons of hot water it can deliver in the first hour of operation.

Heat pump water heaters are the next largest, usually in vertical height. Instead of generating heat directly, these units use electricity to move heat from one location to another, usually drawing heat from the ambient air.

The most compact system is a tankless water heater. The systems are small because they don’t have storage tanks; instead, they heat water on demand as it flows through the unit. These units use the GPM measurement just like faucets and showerheads. Still, choosing the right tankless unit can be challenging.

What Size Water Heater Do I Need? Calray Boilers Has the Answer

Call for an Assessment

Selecting the right size water heater for your building is not a straightforward choice. You must consider many factors, including how many people will need hot water at any given time.

Calray Boilers can help you determine what size water heater your property needs. All you have to do is call us at 212-722-5506 and schedule an assessment. Our team will visit your property to inspect the existing system and determine its efficiency. Before we leave, you will have an estimate for a new efficient water heater and its installation.

Our Privacy Policy

Omnia Mechanical Group(the “Company”) strives to ensure the highest standards for property listings and customer information privacy. Please review the following statement to learn about our company practices and policies. Please be aware that our Privacy Policy is subject to change at any time.

1. Purpose.

This Privacy Policy (“the Policy”) provides information on how the Company uses your personal information. By agreeing to the Policy, you agree to our collection and use of your personal information as described in the Policy. This Privacy Policy is effective for all new users of

2. Personal Information.

You can browse some areas of (“the Website”) without being a registered user. However, certain activities do require registration. (You consent to the transfer and storage of your information by registering with

3. Use of Information.

Our primary purpose in collecting personal information is to provide you with a safe and user-friendly experience. For example, the Company may use your personal information to:

  • Improve our services and the Website’s content and layout;
  • Provide the services and necessary customer support you request;
  • Resolve disputes, collect fees, and troubleshoot problems;
  • Track and record customer satisfaction with our services;
  • Protect the Company against error and fraud;
  • Inform you of special promotions and announcements;
  • Enforce our agreements, terms, conditions, and policies; and
  • As otherwise described to you at the time of collection.

We may occasionally ask you to complete optional surveys. These surveys are used to improve and customize your experience with

The Company always provides you the ability to opt-out of further communication such as promotions and surveys; see the Opt-Out section below.

The Company does not share any of your personal information with outside organizations, companies, individuals, etc. The only exception to this standard is if such a disclosure is reasonably necessary to respond to any and all legal processes.

4. Links to Other Sites.

The Website may have links to other websites that may collect personally identifiable information about you. The Company is not responsible for the privacy practices of the content of those linked websites.

5. Safety & Security Precautions.

The Website has strict security measures in place to protect you and your information from fraud. Once your information is provided to Omnia Mechanical Group, we strive to ensure the confidentiality of your identity and information.

6. Opt-Out.

The Company provides you with the opportunity to opt-out of receiving promotional and other non-essential, marketing-related communications from Omnia Mechanical Group. If you would like to opt-out of these select communications, please see any of the Company’s email communications and follow the directions indicated.

7. Account Protection.

Your password ensures the security of your account. When choosing a password, the Company suggests using various characters. It is highly recommended that you do not disclose your password to anyone. (If you do disclose your password or your personal information with others, you are responsible for all actions taken in the name of your account.) If the security of your password is compromised for any reason, please contact the Company immediately.

8. Accuracy of Information

The Company does not guarantee the accuracy of information for any and all of its properties on the Website, and is not responsible for any errors or misrepresentations (made by Renters, the Client, or otherwise).

9. Cookies

The Company may place a small cookie on your computer’s hard drive. This allows us to personalize your use on the Website. In order to maximize the functionality and usability of the Website, you must set your browser’s preferences to allow both permanent and temporary cookies.

10. Changing Your Personal Information.

Should your personal information change, please immediately update your information on the Website. This will ensure the accuracy of our records. The Company does retain personal information from closed accounts in order to comply with law and collect and disburse any fees owed.

11. Third Parties

This Privacy Policy addresses only the use of information we collect from you. Since does not control the privacy policies of third parties, you are subject to the privacy policies of those third parties. It is advisable that you consult with the management of third parties before you disclose your personal information to others.

12. General

We may amend this Privacy Policy at any time by posting the amended terms on the Website. All amended terms are immediately effective after they are initially posted on the Website.

13. Privacy Policy Questions & Concerns

Questions and/or concerns regarding the Policy should be emailed to the following email address: