The right unit: lumens, not watts

Watts measure power consumed, not light produced. Lumens measure the light output you actually see. The ratio — lumens per watt, written lm/W — is called efficacy. A higher efficacy means you get more light for less electricity.

When manufacturers label a bulb "60 W equivalent", they mean it produces roughly the same lumens as a 60 W incandescent (about 800 lm). The actual wattage of a modern LED doing that job is around 8–10 W.

The formula: annual electricity cost per bulb

The calculation is straightforward. Two steps:

• Step 1 — energy used per year: kWh/year = watts × hours/day × 365 ÷ 1 000
• Step 2 — cost per year: cost = kWh/year × tariff (S$/kWh)

That is all there is to it. Everything else is just plugging in your assumptions — which you should always state explicitly so anyone can verify or adapt the numbers.

Worked example: living-room ceiling light

Suppose you have a single ceiling light point in your living room. You use it for about 5 hours a day. You are deciding between a 60 W incandescent (legacy fitting) and a 9 W LED that produces the same ~800 lm.

Assumptions

• Usage: 5 hours per day, every day (365 days/year)
• Incandescent: 60 W
• LED replacement: 9 W, same ~800 lm output
• Electricity tariff: S$0.2972/kWh (SP Group regulated household tariff, Q2 2026, inclusive of GST — as of April–June 2026; check your latest SP Group bill for the current rate, which is revised quarterly)

Incandescent

kWh/year = 60 W × 5 h/day × 365 days ÷ 1 000 = 109.5 kWh/year

Cost/year = 109.5 × S$0.2972 = ≈ S$32.54/year

LED

kWh/year = 9 W × 5 h/day × 365 days ÷ 1 000 = 16.4 kWh/year

Cost/year = 16.4 × S$0.2972 = ≈ S$4.87/year

Saving

Annual electricity saving per bulb: S$32.54 − S$4.87 = ≈ S$27.67/year

If a quality LED costs, say, S$8–12 at retail, it pays back its purchase price within the first year in electricity savings alone — before you even count the fact that you will replace the incandescent roughly 15–25 times in the LED's lifetime.

Annual cost comparison table: several bulb types at the same point

All figures below use the same assumptions: one bulb, 5 h/day usage, 365 days/year, S$0.2972/kWh tariff. Light output is approximately equivalent (~800 lm) across all rows.

Other factors: colour temperature, CRI and dimming

Colour temperature (Kelvin)

LEDs come in a range of colour temperatures. The most common for homes are:

• Warm white (2 700–3 000 K): yellowish, similar to incandescent — comfortable for bedrooms and living areas.
• Neutral white (3 500–4 000 K): balanced, good for kitchens and workspaces.
• Cool white / daylight (5 000–6 500 K): bluish-white, crisp — common in offices; can feel harsh in bedrooms.

Incandescents and halogens are inherently warm (~2 700 K). CFLs are available in warm or cool, but colour rendering can be inconsistent. LEDs give you the widest choice and the most consistent output.

Colour Rendering Index (CRI)

CRI measures how accurately a light source renders colours compared to natural daylight (reference: CRI 100). For most home rooms, a CRI of 80+ is acceptable. For spaces where colour matters — a wardrobe, an art wall, a vanity mirror — look for CRI 90+ LEDs. This detail is worth reading on the box; cheap LEDs often omit the figure, which is itself a warning sign.

Dimming

Standard incandescents and halogens dim on any traditional leading-edge dimmer. LEDs and CFLs dim only if the bulb is explicitly labelled "dimmable" and you have a compatible dimmer switch — often an LED-specific trailing-edge dimmer. Pairing a non-dimmable LED with a dimmer causes flickering, buzzing, or early failure. If you are renovating and want dimmable lighting throughout, confirm compatibility between your LED brand and your dimmer at the time of purchase.

Lifespan and replacement cost

Lifespan matters as much as electricity cost. Running the same 5 h/day assumption:

• Incandescent at 1 000 h rated: burns out in roughly 200 days — under 7 months. You replace it about 1.8 times per year.
• Halogen at 3 000 h: lasts roughly 1.6 years per bulb.
• CFL at 10 000 h: lasts roughly 5.5 years.
• LED at 20 000 h: lasts roughly 10–11 years.

Over a 10-year period, you would buy roughly 18 incandescent bulbs, 6 halogens, 2 CFLs, or 1 LED for the same light point. The sticker price of the LED is almost always offset many times over by avoided purchases — plus the hassle of changing bulbs in ceiling fittings.

Singapore-specific context

Singapore's tropical environment runs air-conditioning heavily, which makes any heat-generating light source doubly inefficient: incandescents and halogens emit around 90% of their energy as heat, adding to the cooling load. LEDs run far cooler — a meaningful secondary benefit in an air-conditioned home.

Singapore's regulated electricity tariff is reviewed quarterly by the Energy Market Authority (EMA) and distributed by SP Group. As of Q2 2026, the household tariff is 29.72 ¢/kWh inclusive of GST. Check the SP Group website or your latest utility bill for the current rate before doing your own calculations.

If you are planning your lighting layout during a renovation, visit the Balestier Road cluster (traditionally Singapore's main lighting and bathroom showroom district) or major home-improvement retailers for a wide range of LED fittings — see our guide on where to buy renovation materials in Singapore. When choosing finishes and materials for the same renovation, the renovation materials guide covers the full framework.

If you are also thinking about aircon efficiency alongside lighting — the two together account for the bulk of most households' electricity bills — see how many indoor units a multi-split system can run.

Practical buying guide

When buying LEDs in Singapore, look for:

• NEA Energy Label: Singapore's mandatory energy label appears on light bulbs sold locally. More ticks = more efficient. Prefer 3–4 ticks.
• Lumens stated: ignore watt-equivalence marketing; check the actual lumen figure for the brightness you need.
• CRI ≥ 80 for general use, CRI ≥ 90 for colour-critical areas.
• Beam angle: narrow spot (~25–36°) for accent/task; wide flood (~60–120°) for ambient ceiling lighting.
• "Dimmable" label if your fittings use a dimmer switch.
• 230 V / 50 Hz: Singapore's mains standard. Most bulbs sold here are already rated for it, but confirm for any bulb bought overseas or online.

Planning your lighting zones before renovation — which rooms get warm white, which get neutral, where accent lighting goes — is much easier when you can visualise the space at real scale. StoreySG lets you experiment with room layouts and finishes in your actual floor plan before any fittings go up.

Electricity cost figures are illustrative calculations based on stated assumptions. Tariff data sourced from SP Group Q2 2026; verify the current rate on your bill before making purchasing decisions.