Why LEDs use less electricity
A traditional incandescent bulb makes light by heating a thin wire until it glows, and most of the electricity it uses ends up as heat. Halogen bulbs work in a similar way. A light-emitting diode (LED) produces light by passing current through a semiconductor, which converts a much larger share of the electricity into light. The result is that an LED producing the same amount of light generally uses far less power, and runs cooler.
LED bulbs also tend to last much longer than older types, so they need replacing less often. Their purchase price is usually higher, but they often cost less over time. Because lighting is only one part of a home’s energy use, the saving will be modest compared with heating, so think of it as a sensible upgrade rather than a solution on its own.
Read brightness in lumens, not watts
Watts measure how much electricity a bulb uses. They used to be a rough guide to brightness, because all bulbs worked in a similar way, but that no longer holds. For brightness, look for lumens, which measure the amount of light a bulb produces. Higher lumens means brighter light.
Packaging usually shows both numbers. A useful approach is to check the lumens of the bulb you are replacing, if it states them, and choose an LED with a similar or slightly lower lumen figure. If you do not know, think about the room: reading lamps and kitchens usually want more light, while bedrooms and hallways are happy with less. There is no single right number, because it depends on room size, wall colour and personal preference.
Wattage is still worth reading, but as a measure of running cost, not brightness. Comparing two LEDs with the same lumens, the one with the lower wattage is more efficient.
Colour temperature
Colour temperature describes whether light looks warm (yellowish) or cool (bluish-white). It is measured in kelvin, shown as a number with a K. Lower numbers give warmer light and higher numbers give cooler, more daylight-like light. As a general rule:
- Warm white suits living rooms and bedrooms.
- Neutral or cool white is often chosen for kitchens, workspaces and bathrooms.
This is a matter of taste, not efficiency, so choose what feels comfortable. Mixing very different colour temperatures in one room can look uneven, so it is worth buying a matching set.
Other label details worth checking
- Fitting. The cap type must match the lamp or fitting, such as screw or bayonet, and the various small spotlight types. Check the existing bulb or the fitting’s markings before buying.
- Shape. Some LEDs look like classic bulbs, others are spotlights or candle shapes. A bulb that does not fit inside a shade or enclosed fitting can overheat.
- Dimming. If a light is on a dimmer, you need a bulb marked as dimmable, and often a dimmer switch that suits LEDs. A non-dimmable bulb on a dimmer can flicker or fail early.
- Beam angle. For spotlights, a narrower angle gives a focused beam and a wider angle spreads light.
- Colour rendering. Some labels give a rating of how accurately colours look under the light. A higher figure usually means more natural colours, which can matter for kitchens and places where you apply make-up or do close work.
- Efficiency labels. Many places require an energy rating on lighting packaging, similar to the system used on household appliances. Scales have been revised in some regions, so a rating on a new bulb cannot be compared directly with an older one. For how these scales work in general, see the explanation of energy labels.
- Lifetime and warranty. Claimed lifetimes are estimates, usually under test conditions. Heat, frequent switching and poor fittings can shorten real life.
Practical tips for choosing
Start with the lights used the most, such as the kitchen, living room and hallway, because switching those gives the largest benefit. Replace working bulbs when convenient, or as they fail, rather than throwing away usable ones; the manufacturing footprint of a new bulb is spent before it saves anything. Outdoor and bathroom lights need bulbs and fittings rated for damp conditions. Cheap, unbranded bulbs from unknown sellers may not meet safety standards, so buy from reputable retailers and look for the relevant safety marking for your region.
Smart bulbs add features like colour change and remote control, but they draw a small amount of power continuously while waiting for commands. Whether this is worth it depends on your use.
Disposal
Old incandescent and halogen bulbs are generally handled as general waste in many places, though local rules vary. Compact fluorescent lamps (CFLs) and fluorescent tubes contain small amounts of mercury, so they should not go in household bins. LED bulbs contain electronic components and are often classed as electrical waste in many regions.
For all of these, check your local council or retailer for collection points, as many shops and recycling centres accept used bulbs. Handle broken glass with care, and for a broken CFL, follow local guidance on ventilating the room and cleaning up, because it involves mercury. Do not put bulbs in household glass recycling, since the glass is a different type and can contaminate the stream. If you are unsure, ask your local waste authority, as rules differ widely. Disposal advice for batteries and small electricals is similar in spirit, and the principle of keeping electronics out of general waste applies throughout.