Which LED Bulbs Use the Least Electricity?
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If you want LED bulbs that use the least electricity, the number to look at is not the watts on the box on its own. It is how much light you get for each watt, and how many hours the light is actually on. This guide shows how to compare bulbs, works through the sums with real figures from our range, and lists simple ways to cut the electricity your lights use.
1. Compare lumens per watt, not just watts
Watts measure the electricity a bulb uses. Lumens measure the light it gives. Divide lumens by watts and you get the bulb's efficiency: the higher the number, the more light you get for the same electricity.
| Bulb (from our range) | Watts | Lumens | Lumens per watt |
|---|---|---|---|
| Synerji LED T8 tube with microwave sensor | 18W | 1800 | 100 |
| Synerji 9W LED stick lamp | 9W | 850 | 94 |
| Synerji 9W smart LED A60 globe | 9W | 800 | 89 |
| Synerji 4.5W smart LED GU10 | 4.5W | 400 | 89 |
| Synerji 7W LED stick lamp | 7W | 600 | 86 |
| Synerji 6W A60 LED globe | 6W | 480 | 80 |
| Synerji 4.2W LED candle bulb | 4.2W | 300 | 71 |
Lumen and watt figures are taken from each product listing; lumens per watt is simply lumens divided by watts, rounded. For comparison, an old 60W incandescent globe gave roughly 800 lumens, the same light the 9W smart A60 globe gives for 9W.
2. Choose the lowest wattage that gives enough light
The cheapest bulb to run is the one with the lowest wattage that still lights the space properly. A bedside lamp or a passage may only need 300–500 lumens, while a kitchen ceiling light or a garage may need much more. Buying a brighter bulb than the room needs wastes electricity every hour it is on.
- Bedside and table lamps: a 4.2W candle bulb (300 lumens) or a 6W A60 globe (480 lumens).
- Main ceiling light in a bedroom or study: an 800-lumen globe such as the 9W smart A60.
- Downlights: a GU10 lamp in each fitting. Our 5W GU10 is a direct replacement for halogen GU10 lamps.
- Garages, storerooms and workshops: LED T8 tubes give a lot of light per watt.
3. Work out what a bulb costs to run
You can work out the electricity any bulb uses with one sum:
watts × hours on ÷ 1000 = kilowatt-hours (kWh)
For example, a 6W globe that is on for 5 hours a day uses 6 × 5 ÷ 1000 = 0.03 kWh a day, or 0.9 kWh over 30 days. Multiply the kWh by the rate per kWh on your municipal or Eskom bill to get the cost in rand. Because the rate differs from area to area and changes each year, use the figure on your own bill.
4. Let the light switch itself off
The hours a light is on matter as much as its wattage. Sensors and smart control cut those hours without you having to remember:
- Day/night sensor globes turn on at dusk and off in daylight. The Synerji A60 globe with day/night sensor (9W, 480 lumens) suits porches, entrances and passages. Fit it in a light that stays switched on so the sensor can do the work.
- Motion sensor tubes only run while a space is in use. The Synerji T8 tube with microwave sensor has the sensor built in, for passages, stairwells, storerooms and parking areas.
- Smart globes such as the Synerji smart range connect over Wi-Fi to the Smart Synerji app and work with Amazon Alexa and Google Home, so you can set schedules, dim them and switch them off from your phone.
5. Dim where you can
A dimmed LED uses less electricity than the same LED at full brightness. If you want to dim, choose a bulb marked dimmable, such as the 7.2W dimmable A60 globe or the 6.5W dimmable GU10, and ask your electrician to fit a dimmer made for LED lamps. Non-dimmable bulbs should not be used on a dimmer.
Frequently asked questions
Which LED bulb uses the least electricity?
The one with the lowest wattage that still gives enough light for the room. To compare bulbs, divide lumens by watts: in our range, LED stick lamps and T8 tubes give the most light per watt.
Do LED bulbs use electricity when switched off?
A standard LED globe on a normal switch uses none when the switch is off. Smart globes stay connected to Wi-Fi so they can respond to the app, which uses a small amount of standby power.
How many lumens do I need to replace a 60W globe?
About 800 lumens.
Is a lower-watt LED always dimmer?
Not always. Two bulbs with the same wattage can give different amounts of light, which is why lumens are the better guide to brightness.
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All LED bulbs · LED GLS globes · Smart LED lamps · Decorative bulbs
For help identifying a fitting, see our guide to types of light bulbs in South Africa. Delivery across South Africa takes 3–5 business days and is free on orders over R2,000 (R150 on smaller orders).