Water Heater, Aircon, Induction Hob: Which Appliances Need Their Own Circuit

Why some appliances get their own circuit

Most of the sockets in your home share a circuit. Your bedroom lamp, your phone charger and your fan might all trace back to the same breaker in the DB box, because none of them draws much power and it is unlikely they will all peak at once.

Some appliances are different. They draw heavy current, they draw it continuously, and they are often in wet locations. For those, sharing a circuit creates two problems. The circuit trips whenever the heavy appliance runs alongside anything else, and a fault in that appliance takes down everything else on the circuit with it.

The solution is a dedicated circuit: its own cable from the DB box, its own breaker, sized specifically for that appliance and nothing else.

The appliances that need one

Storage and instantaneous water heaters. Not optional. A water heater draws heavy current, runs for extended periods, and sits in the wettest room in the house. It needs its own circuit and its own isolating switch outside the bathroom, so it can be cut off without entering the wet area. Instantaneous heaters draw more than storage heaters and need heavier cable accordingly.

Air conditioning. Each unit, or each system, needs its own supply with an isolator. Compressors draw a surge on startup that is well above their running current, which is exactly the kind of load that causes nuisance tripping if it shares a circuit with your fridge.

Induction hobs and built in ovens. These are among the heaviest loads in a modern kitchen. A full sized induction hob can draw more than every other kitchen appliance combined. It needs a dedicated circuit sized to the manufacturer's specification, and this is the single most common electrical gap discovered mid renovation, because people choose the hob after the wiring is planned.

Washer dryers and heat pump dryers. A washing machine alone is usually fine on a kitchen or service yard circuit. A combined washer dryer, or a separate dryer with a heating element, is a heavy continuous load and is better separated.

EV chargers. If this is even remotely on your horizon, raise it early. The load, the cable route and the metering arrangement are a different conversation from the rest of your home wiring, and in an HDB or condo context there are building side approvals involved.

What is usually fine on a shared circuit

Fridges, microwaves, kettles, air fryers, rice cookers, televisions, computers, fans and lighting are all normally fine sharing appropriately sized circuits.

The caveat is quantity. A modern kitchen might have a kettle, an air fryer, a microwave, a rice cooker and a coffee machine, and if two or three run simultaneously on one circuit, you will trip it. This is why the trip so often happens while cooking a proper meal and never at any other time. In that case the answer is usually not a dedicated circuit for each appliance but an additional kitchen circuit so the load is split across two.

Isolators, and why bathrooms are treated differently

Bathrooms have their own rules because water dramatically reduces the resistance of the human body. What would be a harmless shock on dry skin can be fatal on wet skin.

This is why a water heater's isolating switch is mounted outside the bathroom, or as a pull cord type inside it. It is why sockets are generally not permitted inside bathrooms in Singapore homes. It is also why the RCCB matters most here. The failure mode of a water heater element, insulation breaking down and letting current leak to earth, is precisely what the RCCB is designed to catch.

If you have a water heater and no RCCB in your board, that combination is worth addressing before anything else on your list.

Planning this during a renovation

The cheapest time to add a dedicated circuit is before the walls close. The most expensive time is after.

Confirm your appliances before wiring is finalised. Not the category, the actual model. An induction hob's requirement varies significantly between models, and the electrician needs the specification, not "an induction hob."

Give the electrician the appliance manuals or spec sheets. Every appliance states its power requirement. This removes guesswork entirely.

Check spare capacity in your DB board early. If your board has no spare ways, every dedicated circuit you want triggers a board upgrade. Better to know that at the start of the renovation than in week six.

Sequence it correctly. Electrical first fix happens before plastering, tiling and carpentry. If the appliance decision is still open at that point, either the wiring gets guessed or the schedule slips.

Think about where the isolators go. They need to be accessible. An aircon isolator behind a fitted wardrobe is technically installed and practically useless.

Older flats: the mismatch problem

Flats built before the mid 1990s were wired for a household that owned considerably less. Many were provisioned for a 30 amp supply, where a modern home often needs 40 amps or more once you add a water heater, multiple aircon units and a modern kitchen.

Upgrading that main supply capacity is a separate process involving SP Group, not something a contractor simply does inside your flat, and it needs to be identified early because it has its own lead time. If you are buying an older resale flat and planning a full renovation, ask about the supply capacity in the first conversation rather than the last.

What this costs

As a rough guide in the current market, a dedicated water heater point is commonly around S$120. An aircon point or isolator typically runs S$120 to S$180 per point. Heavier circuits for induction hobs and ovens cost more because of the cable size and run length.

The number that surprises people is the cost of adding one later. A dedicated circuit installed during a renovation, while walls are open and the board is accessible, might be a fifth of the cost of the same circuit installed two years later with concealment, patching and repainting. If you are on the fence about an appliance, running the cable now and leaving it capped is usually far cheaper than running it later.