A light that switches itself on when you walk in and off when you leave is one of the few smart-home ideas that pays for itself without a phone app. Hega, a new entrant, has launched its range of automatic sensor lights in Bangladesh at an event in Dhaka, and says switches, doorbells, plugs, security systems and home- and office-automation products will follow.
What the product does
The lamps combine a motion sensor with what the company calls intelligent light detection: the lamp turns on when it senses a person and only when ambient light is low, then turns off when the space is empty. The company claims savings of up to 80 per cent against conventional lighting. Country manager Sheikh Al Amin framed the goal as international-standard automation at comparatively affordable prices.
Work the sum
Sensor lighting saves energy in exactly one way: by not being on when nobody is there. That is worth taking literally, because it lets you check the claim for your own rooms in about a minute.
Take a stairwell with a 20-watt LED left on from dusk to dawn — twelve hours — because nobody wants to climb stairs in the dark. That is 240 watt-hours a day. Now suppose people actually use those stairs for a total of one hour across the evening. A sensor lamp burns 20 watt-hours instead of 240, a saving of about 92 per cent. For that room, "up to 80 per cent" is conservative.
Now take a living room where the family sits from seven until eleven. The light would be on for those four hours either way. A sensor saves the few minutes at the end when everyone has gone to bed and someone forgot — call it five per cent on a good day, and nothing at all if the household already switches off.
So the claim is neither marketing nonsense nor a general truth. It is a statement about occupancy patterns, and it holds wherever a light currently burns for hours with nobody under it: stairwells, corridors, garages, store rooms, bathrooms, building lobbies, a mosque's wash area, a shop's back room.
One further honesty, because it is the commonest way these numbers get inflated. If you are replacing an old fluorescent tube or an incandescent bulb, a large part of the saving comes from the LED, not the sensor — an LED uses roughly a fifth of what an incandescent does for the same light. Comparing a new sensor LED against an old incandescent and crediting the difference to the sensor is a comparison that flatters the wrong component.
The two sensor types, and which room each suits
This is the specification that most affects whether you will be happy, and it is almost never on the box.
Passive infrared sensors detect moving heat. They are cheap, reliable, and have two consequences worth knowing. They cannot see through glass or walls, which is usually what you want. And they detect movement of a heat source — so a person sitting still at a desk can stop registering, and the light goes out on someone who has not left. For a corridor or a stairwell that never happens. For a store room where someone might stand still reading a label, it happens constantly.
Microwave sensors emit a signal and detect the change when something moves in it. They are more sensitive to small movements and they pass through thin partitions — which is a feature in a long corridor with an obstruction and a problem in a flat, where the lamp fires because someone walked past on the other side of a plasterboard wall.
So: PIR for enclosed spaces with clear sightlines, microwave for corridors and where coverage matters more than precision. Ask which one, and ask the detection distance in metres rather than accepting "wide coverage".
Three more things to check
Hold time. How long the light stays on after motion stops. Too short and it goes dark while you are still on the stairs, which is both annoying and the reason people disconnect these. Look for an adjustable delay rather than a fixed one.
Lux threshold. The daylight cut-off that stops the lamp firing in a bright room. It should be adjustable, because a fixed threshold set for a European winter behaves oddly here.
Voltage tolerance. This is the specification that decides how long the lamp lasts in Bangladesh. The LED itself rarely fails; the small power supply driving it does, and it fails from voltage swings rather than from age. A wide input range — something like 170–250 V — is what separates a lamp that lasts five years from one that lasts one.
Two costs the claim leaves out
Standby draw. A sensor lamp is never fully off. The sensor and its electronics draw a small current continuously, typically under a watt. For one lamp that is negligible. For forty lamps across an office building it is a constant load that quietly reduces the headline saving, and you should ask the supplier for that figure.
Switching cycles. A lamp in a busy corridor may switch on and off hundreds of times a day rather than twice. LEDs tolerate this well; cheap drivers sometimes do not, and a lamp that fails after eighteen months in a high-traffic corridor has usually failed there rather than in the diode.
Which is why the warranty question is really a service question. Sensor lamps fail at the driver or the sensor, so what matters is whether there is a local replacement route rather than what the certificate says.
Why a local launch is worth something
Smart-home products here have mostly arrived piecemeal through importers with no support behind them, which is how a category gets a reputation for not lasting. A brand launching with a local office, a price position and a product roadmap is a modest but real difference.
And of all the smart-home categories, sensor lighting is the one where you can check the vendor's maths yourself. Count the hours a light currently burns with nobody under it, multiply by the wattage, and you have the saving before you have bought anything.
