Central vs. Individual Water Heating?

Owners of homes with multiple bathrooms (mostly landed) usually struggle with the decision of whether to use a central water heater piped to all locations or to use individual heaters for each bathroom. There are pros and cons for each decision. In the interest of narrowing our scope, we will only consider storage heaters.

1. Initial Cost

As illustrated above, using several individual heaters will usually cost more than using a single system.

2. Running Cost

Each individual heater is rated 3.0kW. Using a few heaters in the house means your electrician must accommodate for a higher maximum power load for water heating.

If you use a central heater, the maximum power load will be lower.

3. Shower Convenience

Individual heaters are installed close in proximity to the shower area so users can get their hot water faster.

It will take a few minutes for water from a central heater to flow to several bathrooms from the central heater, but the long wait time can be reduced significantly by installing a circulating pump. The pump may be installed at an additional cost.

4. Installation

Individual heater systems are traditionally placed above the false ceilings of each bathroom. Comparatively larger central heaters are weatherproof and may be placed indoors or outdoors. They can be installed at the roof area, a/c ledges or basements. The installation costs of several heaters will cost more than a single heater unit.

If the roof or a/c ledges are not as accessible and a crane is required to hoist the heater to a desired floor, installation costs may increase.

5. Utility Consumption

If heaters are sized for individual bathrooms, they should be at least 40 lit for each bathroom. When sizing for central heaters, instead of taking 40 lit and multiplying that capacity by the number of bathrooms, you have more leeway based on the assumption that not all members of the family shower at the same time.

In the example above, individual heater systems require 40 lit for each bathroom, so for the whole house, total capacity is 200 liters. The recommended central heater can be smaller; it is sized at 150 liters. A smaller, central heater also means lower bills due to less unnecessary heating, and lower chances of heat loss to the environment.

6. Maintenance

Maintaining several heaters is probably going to cost more than maintaining a single one. This is especially so if the individual heaters are installed above false ceilings. Replacing a water heater without a false ceiling will cost around $150 but replacing a water heater with a false ceiling will cost at least $300. Imagine having to do this a few times! This is one of the biggest drawbacks of maintaining individual systems.

Homeowners also do not like dealing with the mess of ceiling and plumbing works in their bathrooms every now and then. Bathrooms are very personal spaces! Central units are commonly installed at the roof or a/c ledge, installers only need to access these areas if a fix is required.

A downside of using a central heater is if that one heater is down, the whole household may be out of hot water for a few days. Homeowners who are concerned about this may opt to get two smaller heaters installed in parallel instead of one large one.

7. Pressure & Temperature

As the type of heaters we are considering are all storage types, pressure and temperature throughout the whole house should be fairly consistent.

8. Aesthetics

Central water heaters placed at roof area allow for raised bathroom heights.

This last section addresses the placement of heaters, which in turn affects the design of your bathrooms. If individual heaters are placed above false ceilings, there will be a drop in height of the bathrooms to accommodate for a larger false ceiling space. Central heaters may be installed at the roof or a/c ledge, allowing designers to raise bathroom heights and make the area look larger.

On a final note, here are four important factors to take note of before making a decision.

4 Important Considerations

1. Existing Piping

You should only consider changing from a central system to an individual system or vice versa if you are doing a full scale renovation. Otherwise, use your existing layout. Removing existing pipes and laying new ones for the whole house are not only expensive, the process will involve extensive hacking and drilling.

2. Type of Heater

If you are using a renewable energy water heater like solar or heat pumps, bear in mind that the nature of their heating process requires a large tank. As such, it will be preferable to use a central system to save on initial cost.

3. Bathroom Placement

Always have your floor plan handy. Your bathroom or kitchen placement matters. If your hot water points are spaced very far apart from each other, your water piping for a central system may cost more than that of an individual system.

When in doubt, send your floor plans to a water heater specialist and be prepared to answer a series of questions on your usage, bathroom fittings, and minimum and maximum expected occupancy at home. These will help us determine which water heater is best for you and how the system should be installed.

4. Plan Water Heaters Early

Planning must be done early! Wiring and water pipes are run at early stages.

We’ve met so many clients who left their water heater decisions to the last minute as they were not advised that their choice of heaters would affect water piping. When all your tiles are up, you cannot make very many changes! Water piping is decided very early in the build stage of the house, together with electrical works.



Amanda is an education specialist at AOS Bath. She enjoys building a trusted network by sharing knowledge. Making difficult concepts simple and engaging is rewarding, on both ends.