For most Airbnb and homestay condos in Malaysia, the right water heater is one instant heater per bathroom, sized to the shower head you actually fit. A storage tank only makes sense for a rain shower, a bathtub or several taps at once, and then it must be big enough for the last guest in the queue.
That is the short answer. The rest of this article is the part the appliance shops leave out: their guides are written for a family that showers at different times. A homestay is different. Four to six people come back from Legoland, Desaru or a day in Singapore at the same hour and all want a shower within forty minutes. That single habit decides which heater works.
Instant or storage water heater: which is better for a homestay?
| Situation in the unit | What usually works | Why |
|---|---|---|
| Condo, 1–2 bathrooms, normal shower head | One instant heater in each bathroom | Hot water never "runs out"; each bathroom works on its own |
| Rain shower or wide overhead head | Storage tank, or a high-kW instant unit after an electrician checks the circuit | A low-kW instant unit cannot heat that much water flowing that fast |
| Bathtub that guests will fill | Storage tank sized for the tub | Instant units fill a tub slowly and lukewarm |
| Landed house, kitchen and bathrooms on one heater | Storage tank, or separate instant units per bathroom | One tank can feed several taps; one instant unit feeds only one |
| Low water pressure on a high floor | Instant unit with a built-in pump, after measuring the flow | Many instant units need a minimum flow before they switch on |
The reason instant wins in most homestay condos is simple: each bathroom has its own heater, so the second and third guest get the same water as the first. Free Malaysia Today's buyer's guide puts it plainly: an instant unit serves one outlet, a storage unit can serve several, and a storage tank takes 10 to 30 minutes to heat depending on its size.
Why does the third guest get a cold shower from a storage tank?
Because a tank holds a fixed amount of hot water and then needs time to reheat. Here is the arithmetic, as an example only (tap water at about 28°C, tank set to 65°C, shower at 40°C):
- A 30-litre tank mixes out to about 92 litres of 40°C water. At 8 litres a minute, that is roughly 11 minutes of showering.
- A 50-litre tank gives about 154 litres, roughly 19 minutes.
- Four guests showering 8 minutes each at 8 litres a minute need about 256 litres.
So with a 30-litre tank, guest two finishes the hot water and guests three and four wait for the reheat, which for a 30-litre tank on a 2.5 kW element is around half an hour in this example. In a family home nobody notices. In a homestay it becomes "no hot water" in a review. If you do choose storage, size it for the whole group, not for one person.
What kW instant water heater do you need?
The number that matters is not the kW on the box alone. It is kW against how many litres per minute your shower head lets through. A rough rule from basic physics: 1 kW raises 1 litre per minute of water by about 14.3°C. Using 28°C tap water as the example:
| Shower flow | 3.6 kW unit: water comes out at about | 6 kW unit: water comes out at about |
|---|---|---|
| 4 L/min (water-saving head) | 41°C | 49°C |
| 6 L/min (normal head) | 37°C | 42°C |
| 8 L/min | 34°C | 39°C |
| 10 L/min (rain shower) | 33°C | 37°C |
These are theoretical figures; real units lose a little more. The lesson is that a cheap low-kW heater with a big rain-shower head gives a lukewarm shower, and guests blame the unit, not the physics. Either keep a normal or water-saving hand shower with a modest instant heater, or move up in kW and ask an electrician whether the bathroom point can take it. As a rough guide, 3.6 kW draws about 16 amps and 6 kW about 26 amps at 230 volts.
A simple test before you buy: hold a 5-litre bucket under the existing shower and time it. 30 seconds means 10 litres a minute; 60 seconds means 5.
How much electricity does a homestay water heater use?
Less than most owners fear, but it is the owner's bill. As an example: a 3.6 kW instant heater running 10 minutes uses about 0.6 kWh. In our monthly running-costs article we worked out that an extra kWh in the 400–700 kWh band costs about 57.6 sen on the TNB domestic tariff. That puts one 10-minute shower at roughly RM0.35, and eight showers in a two-night stay for two guests at roughly RM2.80. These are illustrative numbers, not a promise; guests decide how long they shower.
Storage tanks add a cost instant units do not have: if the tank is left on all day it keeps reheating water that nobody uses. A timer, or a switch the cleaner turns off at checkout and the guest turns on at arrival, reduces that. We have not measured the standing loss of any particular tank, so we will not put a figure on it.
If your unit already gets close to 600 kWh in busy months because of the aircond (see our aircond guide), the heater is part of what pushes it over.
What safety checks matter before guests use it?
- ST-SIRIM label on the unit itself. Storage and instantaneous water heaters are on Suruhanjaya Tenaga's list of regulated electrical equipment, and a regulated product needs a valid certificate of approval and the ST-SIRIM label. A label only on the box is no longer accepted. Cheap online imports without the label are the ones to avoid.
- Earth leakage protection. Many instant units have a built-in ELCB with a test button. Also press the test button on the RCCB in the DB box; if it does not trip, call an electrician before the first guest.
- Installed by a competent electrician, with proper earthing. This is not a DIY job in a unit strangers will use.
- For storage tanks: the relief valve and where its water goes. A tank in the ceiling that leaks or discharges can wet the ceiling and the unit below. We wrote about what happens next in a guest caused a water leak to the unit below. Free Malaysia Today's guide warns that tanks can leak after many years from corrosion.
This is general information, not electrical advice; follow your electrician and your building management's renovation rules.
How do you stop "no hot water" messages from guests?
Most of these messages are not broken heaters. They are a switch guests did not find. In many Malaysian condos the heater switch sits outside the bathroom door, which visitors from abroad do not expect.
- Put a small label on the switch: "Water heater – switch on 1 minute before showering".
- Add one line and a photo to the house guide (see our amenities checklist).
- Make "run the hot water for 30 seconds in every bathroom" part of the turnover checklist, so a dead heater is found by the cleaner, not by a guest at 11pm.
- For instant units, know the model and where to buy the same one; a like-for-like swap is usually quick.
What should you ask before you buy or accept a quote?
- What is the flow of the shower head we are fitting, in litres per minute?
- What kW is the heater, and can this bathroom's wiring and breaker take it?
- Does the unit carry the ST-SIRIM label on the body, and does it have a built-in ELCB?
- For a tank: how many litres, how long to reheat, and where does the relief valve drain?
- Is installation, the isolation valve and removal of the old unit in the quoted price? (Our guide to comparing renovation quotes covers the other lines.)
Then test hot water in every bathroom at handover, as in our handover checklist.
The honest part
If your unit already has working instant heaters with sensible shower heads, keep them. Replacing them earns a renovation contractor money, including Magic Touch, and does little for your guests. Under a management plan where electricity is the owner's expense, a heavier heater is your cost, not the manager's, so ask about it. And no heater choice guarantees zero complaints: a guest can still miss the switch.
We manage more than 100 units, and the point of this article is one idea: plan the bathrooms for the group arriving together, not for a family showering one by one. If you are fitting out a unit and want the bathrooms planned for that, you can start from Magic Touch.