Water heaters are one of the appliances most homeowners only buy two or three times in their lives. So it is no surprise that the choice gets made by browsing online price ranges, asking a neighbour, or trusting the recommendation of whoever is selling the unit. Below is the framework we use at AquaShield when a client asks us — without a sales pitch attached.
Step 1: Count the simultaneous draws
The most important question is not "how big should the tank be" — it is "how often do two hot taps run at the same time". An instant heater serves one outlet at a time. A 25 L storage tank serves two cleanly. A 50 L tank handles three. Above that, you need either a larger tank or a multipoint system.
Walk through a typical weekday morning in your household. If a shower and a kitchen tap or two showers are routinely running together, an instant heater will leave someone shivering.
Step 2: Look at the wall behind the unit
Instant heaters draw 3.6 to 6 kW from a dedicated electrical circuit. In older terrace houses the consumer unit may not have spare capacity, and an upgrade can cost as much as the heater itself. Storage tanks draw less peak power but need a structurally sound wall — they weigh 40 to 90 kg full. Soft brick or plaster partitions need bracket reinforcement.
Step 3: Decide what you value most
This is where it gets personal. Different households genuinely value different things, and that is fine.
- If you value low capital cost: an instant heater wins. Units start at around RM 480, fitted.
- If you value simultaneous showers: a 50 L storage tank in a service cupboard solves it once and for all.
- If you value long-term running cost: a solar-assisted system pays back in roughly seven years on the Malaysian climate average.
- If you value zero maintenance: instant heaters have nothing to descale, no anode rod to replace.
- If you live in a high-rise where roof access is impossible: solar is off the table.
Step 4: Match the unit to the bathroom layout
A long pipe run from heater to showerhead means the first 5–10 seconds of every shower will be cold water that was sitting in the line. Instant heaters mount directly above the shower, so the run is metres at most. Tank systems concealed in a service cupboard can be 8–10 metres away, which means longer waits and more wasted water. There are recirculation pumps that solve this — they add roughly RM 1,200 to the installation.
The most common mistake we see: a 50 L tank installed for a single-occupant studio, "for future-proofing". Twelve years of standing heat loss later, the maths is not flattering.
Step 5: Confirm the warranty terms
Brand warranties on heaters range from 1 to 12 years, but the fine print matters. Most warranty cover excludes:
- Hard water damage to elements (relevant in some Selangor areas)
- Pressure damage from a missing or undersized PRV
- Damage from voltage spikes — install a surge suppressor on the dedicated circuit
- Cosmetic enclosure rusting in coastal areas
We document the warranty terms in writing during installation, so you have a clean record if you need to claim five years from now.
A starting recommendation
For a typical Klang Valley terrace house with two adults and two children:
- One 50 L storage tank in the service area, serving the master bath and the kitchen.
- One compact instant heater in the second bathroom, dedicated to that shower.
- Bracket reinforcement, PRV, and earth-leakage protection check on both circuits.
Total fitted cost in 2026 figures: roughly RM 2,800–RM 3,400 including the units, depending on brand. That is the configuration we install most often, and the one our crew runs in our own homes.
Written by Faizal Hamzah, co-founder. Last reviewed March 2026.