Renovating Your Home? Plan the Electrical Before the Walls Close Up

A renovation runs in a fixed order — hack, then services first-fix, then plaster, tile, carpentry, finishes. Your wiring goes in near the start, buried in walls and run above ceilings before anything is closed up. Which means the decisions you make about power and points in the first two weeks quietly shape how your home works for the next ten years. Change your mind after the tiler has left, and you are paying to hack open a finished wall. Here is how to get it right the first time.

Why the electrical plan has to come first

In a Singapore renovation, electrical wiring is "first-fix" work — it goes in at the early, rough stage. The cables are cut into grooves in the walls (electricians call this "chasing") and run above the ceilings before any plastering or tiling starts. Once the finishes are on, moving a single socket or adding a new circuit means hacking, re-tiling and re-painting. The cheapest time to add a point is before the wall is closed. The most expensive is after you have moved in.

That is why the electrical layout should be locked in with your electrician at the design stage — alongside the interior designer's carpentry drawings — not decided on the fly while a worker is already chasing the wall. A good plan on paper costs nothing to change. A wrong one in concrete costs a weekend and a re-tile.

Room by room: where planning pays off

Not every room needs the same attention. These are the ones where a few minutes of planning saves the most grief:

• ›Kitchen — your highest-load room. Oven, induction hob, cooker hood, fridge, microwave, kettle and an instant-boil tap all draw power, and the hob and oven usually need their own dedicated circuits. Set socket positions around the final carpentry — the island, the tall units, the appliance bay — not before it is drawn.
• ›Bathrooms & wet areas — instant water heaters draw heavy current and need their own protected circuit. The heater position has to suit the plumber and the electrician at the same wall, so plan it once, together.
• ›Living & bedrooms — aircon isolators (the little switch that safely cuts power to an aircon for servicing), ceiling points for lights and fans, a TV feature wall with concealed power and data, and simply enough sockets so you are not living on trailing extension cords.
• ›Study / home office — a dedicated circuit if you run heavy equipment, and hard-wired data points that beat leaning on Wi-Fi for work calls.
• ›Service yard & car porch — weatherproof outdoor points, and increasingly a provision for an EV charger even if you fit the charger itself later.

Will your supply cope? Single-phase limits, loads and your DB

Almost every home in Singapore runs on a single-phase supply. An HDB flat is single-phase — flats built from 1994 (and older blocks that have since been upgraded) get a 40-ampere main, roughly 9 kW of total headroom; some older flats are 30A. Most condo apartments are single-phase too, though the exact rating varies with the development. Three-phase power — the kind that comfortably runs several aircon units, a 22 kW EV charger and heavy appliances at once — is essentially a landed-home supply. A standard HDB flat or condo unit cannot simply be switched to three-phase; only the occasional high-demand penthouse is looked at case by case.

Every heavy appliance you add pulls from that one single-phase supply: an induction hob (its own dedicated circuit — around 16–20A for a two-zone hob, up to 32A for a big four-zone one), a built-in oven, an instant water heater, several aircon units, an EV charger. Stack enough of them on a 40A HDB main and you either trip the main during ordinary use, or run out of empty slots (electricians call them "spare ways") at the distribution board — the grey box of switches on your wall, or "DB" — to add new protected circuits.

So a few things are worth checking before you lock the appliance wishlist:

• ›Does your DB (that grey box of switches) have empty slots — "spare ways" — for the new circuits your renovation needs?
• ›Is your supply big enough for everything running at once? HDB publishes the available electrical loading for each block, and a licensed electrician can check your plans against it before you commit.
• ›Can the main be raised at all? On a single-phase supply it is sometimes possible to increase the main (an HDB flat toward 63A, for instance) — but only with SP Group's approval and where the building's supply allows, so it is never a given. Design your loads around what you actually have.

Your whole flat shares one power budget

A typical HDB flat runs on a single-phase 230 V supply behind a 40 A main — a hard ceiling of about 9 kW (40 A × 230 V) for the entire home at any one moment. Everything switched on at once draws from that same budget. Rough running figures tell the story:

• ›Instant water heater, running — around 7 kW
• ›Induction hob, cooking — around 4 kW
• ›Built-in oven — around 2.5 kW
• ›Kettle — around 2.5 kW
• ›Three aircon units running — around 3.5 kW
• ›Lights, fridge, TV and chargers — around 1 kW

Your board must have an RCCB

One part of the consumer unit is not optional: the RCCB — a life-saving safety switch (its full name is residual current circuit breaker). Picture a guard watching the electricity flow out and flow back; the instant even a tiny amount goes missing because it has found another path to earth — often through a person — it cuts the power in a fraction of a second. That is the difference between a shock you feel and jump back from, and one that stops your heart. Singapore's wiring code, SS 638, requires this 30 mA protection on general-use socket circuits (up to 32A), and in homes on the lighting circuits too — so any properly wired renovation includes it as standard.

On top of the wiring code, EMA requires every home — HDB flat, condo or landed — to have an RCCB (or an equivalent earth-leakage breaker). Many older flats, especially those built before 1985, were never fitted with one; from 1 July 2025 EMA can carry out random enforcement checks, with fines of up to S$5,000 for a home without one. If your place is older, a renovation is the natural moment to bring the board up to standard.

Older flat? We check and upgrade the board as part of any renovation wiring job — WhatsApp us a photo of your DB and we will tell you what is in it.

Points and positions: decide once, live with it for ten years

These are the choices you will live with every day long after the reno dust has settled:

• ›How many sockets, and where — count the things that actually get plugged in, then add a few. Nobody ever complained about one socket too many.
• ›Switching that makes sense — two-way switches for stairs and long corridors, a bedroom switch at both the door and the bedside.
• ›Data, USB and charging points — where the phones live, where the desk sits, where the router goes.
• ›Aircon isolators and ceiling points — placed so they are reachable and not hidden behind a cabinet.
• ›Future-proofing — a spare conduit or a capped-off point for a future EV charger or extra aircon costs very little while the wall is open, and a small fortune once it is closed.

What does renovation electrical work cost?

These are current Singapore market ranges from public renovation and electrician guides — not our price list. Every flat differs (wiring runs, hacking, reinstatement, what is already in the board), which is exactly why any serious quote should be itemised. Use these to sense-check what you are quoted:

Why the same point can cost double

Three things move the numbers. Concealed vs exposed wiring — chasing cables into the wall means hacking, patching, repainting and coordinating with the tiler, so a concealed point costs meaningfully more than surface trunking: some price lists add 10–15%, while designer quotes often run one-and-a-half to two times the exposed rate. Heavy-load points vary widely — a new 15A aircon point is quoted anywhere from about S$110 to S$250 depending on the contractor and property, and HDB's own rule is that flats without upgraded electrical loading need an HDB permit for new 15A points. Board work depends on what is in your board — a like-for-like RCCB swap on a healthy DB is a S$120–300 job, but EMA's own estimate for a full RCCB installation is around S$500 for an HDB flat (S$600 private) — more if rewiring is needed.

One convention to know: many electricians charge a call-out or site-inspection fee (commonly S$60–100, varying by contractor), often waived or offset if the work goes ahead.

What actually goes wrong when the wiring is done cheap

Most bad electrical work looks perfectly fine on handover day — the lights come on, the sockets work, the walls are painted. The problems are sealed behind the plaster and surface months or years later. These are the shortcuts that cause them:

• ›No RCD, or the wrong one — the 30 mA safety switch that cuts power in a fraction of a second when current leaks to earth is the first thing a rushed job skips. The socket still "works", so it passes a casual look, but the fast trip that protects you is not there. A working socket is not proof of a safe socket.
• ›A breaker too big for its cable — the breaker is the safety switch meant to cut power before a cable overheats. Load too many appliances onto a cable that is too thin but pair it with a breaker set too high, and the breaker sits there doing nothing while the thin cable quietly cooks inside the wall, like a fuse that never blows. The signs you can actually notice: warm wall plates, a faint burning smell, or a breaker that trips for no clear reason.
• ›Loose connections buried behind plaster — a half-tight or overstuffed terminal creates resistance, resistance under load creates heat, and sealed behind tiles it slowly arcs and carbonises. It is one of the most common hidden causes of electrical fires in renovated homes.
• ›Hidden junction boxes — joins must stay reachable for inspection. Quick twist-joints tiled over are hidden connections that can loosen and overheat with nothing ever checking them.
• ›No testing, no certificate — the installation must be tested before it is energised, by a Licensed Electrical Worker who stands behind the certificate. "It works today" proves nothing about how it behaves under a fault — and unlicensed, uncertified work can see an insurance claim challenged or denied.

The bit most renovations get wrong: when the trades don't talk

The most common renovation headache is not any single trade doing a bad job. It is the trades not talking to each other.

Look at where the work actually overlaps. A water heater needs a plumber (pipe in, pipe out) and an electrician (a dedicated circuit) at the same wall. An air-conditioner needs power and an isolator (electrical), refrigerant piping and a condensate drain (aircon and plumbing), plus a wall penetration everyone has to agree on. Your kitchen and your bathrooms are exactly where electrical, water and ventilation all meet.

Book those as separate, uncoordinated contractors and you get clashes: a drain routed straight through where the cable should run, an isolator ending up behind a finished cabinet, a wall chased open twice — and, when something is wrong, three trades each pointing at the other two.

There is a licensing reality underneath this, too. Electrical work must be carried out or supervised — and certified — by a Licensed Electrical Worker; and since 1 April 2018, regulated water and sanitary plumbing works must be carried out by a PUB Licensed Plumber (simple jobs like changing a tap are exempt). These are two separately regulated trades that have to meet at the same walls. Getting them (and the aircon) to line up is exactly where a renovation either runs smoothly or turns into a blame game.

Licensing, permits and who signs it off

In Singapore, electrical work must be carried out or supervised by a Licensed Electrical Worker (LEW), and certified by one. In practice, trained electricians do the hands-on wiring while the LEW supervises, tests and signs it off — and carries the legal responsibility for it. What the law does not allow is an unlicensed "handyman" doing your rewiring, DB changes or new circuits with no LEW involved. That certificate is not box-ticking: it is what makes your installation compliant with SS 638, insurable, and safe to live with. If you are unsure who signs what, our LEW explainer walks through the grades and the law.

There is paperwork behind the scenes, and a good contractor handles it for you:

• ›HDB flats — bigger renovations need an HDB renovation permit (usually filed by your contractor or ID), while your LEW carries out, tests and certifies the electrical works and ensures they meet SP Group's connection requirements.
• ›Condos & private apartments — you will usually need your MCST's approval for renovation works, on top of the electrical certification.
• ›Landed homes — more scope, bigger loads and often a three-phase supply, so the design and the sign-off matter even more.

How BSH does it

The single best move is timing: bring the electrician in at the design stage, not after the walls are up. That is the moment the whole plan is cheap to get right — and where a licensed contractor earns its keep by catching the load, the coordination and the compliance issues before they are set in concrete.

BSH has been wiring Singapore homes and businesses since 1993 — EMA-licensed, led by Grade 8 LEWs, BCA-registered, bizSAFE and ISO 9001 / 14001 / 45001 certified. The same licensed team that delivers commercial fit-outs and industrial projects can plan the electrical for your home renovation, and coordinate the aircon and plumbing so it all lands as one job.