Light bulbs: why LEDs use less
An incandescent bulb produces light by heating a thin filament until it glows, and most of the electricity becomes heat rather than light. 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 can produce similar brightness while drawing a fraction of the power.
When comparing bulbs, look at lumens (brightness) rather than watts. Watts tell you how much electricity a bulb uses, and lumens tell you how much light it gives. Also look at color temperature, listed in kelvins: lower numbers appear warmer and yellower, higher numbers appear cooler and bluer. Finally, check whether the bulb is dimmable if you use it on a dimmer, since not all are compatible.
A worked example
Suppose an older bulb draws 60 watts and an LED giving similar light draws 9 watts. If the bulb is on for 3 hours a day:
- Older bulb: 60 W x 3 h = 180 watt-hours per day, which is 0.18 kilowatt-hours (kWh).
- LED: 9 W x 3 h = 27 watt-hours per day, or 0.027 kWh.
- Difference: 0.153 kWh per day. Over 365 days, that is about 55.8 kWh per year.
At a price of 0.20 per kWh (an illustrative number, since local rates vary), that is roughly 11.16 in savings per bulb per year. The upfront cost, the hours of use and your actual rate all change the result. Bulbs used for many hours, such as in kitchens, tend to repay the difference sooner than those in a rarely used closet. If you are unfamiliar with these units, the basics are covered in energy units explained simply: a watt measures power, and a kilowatt-hour measures energy used over time.
LEDs also last longer than older bulbs, which reduces replacement. Quality varies, so very cheap unbranded bulbs may flicker or fade early, and rated lifetimes are tested under set conditions.
How appliance efficiency labels work
Many countries require labels on major appliances such as refrigerators, washing machines, dishwashers and air conditioners. Details differ, but common features include:
- An energy consumption figure, often expressed in kilowatt-hours per year or per cycle, based on a standard test.
- A rating scale, such as stars or letter grades, that ranks models against others of the same type.
- Size or capacity information, because a larger model naturally uses more energy and is not directly comparable to a smaller one without that context.
Some labels are mandatory and some are voluntary programs. Rating scales have also been revised in places, so an older “top” grade may not match today’s. Standard tests do not reproduce your household’s habits, so treat the figure as a way to compare models rather than as a precise prediction of your bill.
Minimum performance rules for new products often fall under efficiency standards, which remove the least efficient models from the market over time. This means that even a basic modern appliance can be better than one from many years ago.
What to compare when choosing
- Annual energy use for your size. Compare models of similar capacity and features, using the label’s kWh figure.
- Purchase price versus running cost. A more efficient model may cost more upfront. Multiply the annual consumption by your local electricity rate and by the number of years you expect to keep it.
- Right size. An oversized refrigerator or freezer wastes energy keeping empty space cold. An undersized one may lead to extra loads of laundry.
- How you use it. A dishwasher that is run full and a washing machine used with cooler wash settings will beat any label difference from running them half empty at high temperatures.
- Extra features. Ice makers, large displays and connected features can add consumption. Standby draw is worth a look, and standby power can add up across many devices.
- Repairability and lifespan. An appliance that lasts longer has a smaller footprint over time, because manufacturing also uses energy and materials. This is the kind of question a life cycle assessment tries to answer, though a shopper rarely has that data.
Replace now or wait?
Replacing a working appliance is not automatically the efficient choice. A very old refrigerator, particularly one from several decades ago, can use much more electricity than a modern one, so replacement may pay off. On the other hand, a newer appliance in good order may offer little saving, and manufacturing a replacement carries its own energy and material cost. A simple plug-in power meter can show what an existing device actually draws, which helps you judge whether replacing it makes sense.
Heating-related items such as water heaters, furnaces and heat pumps usually have separate rating systems and different considerations, covered in their own topics.
Rebates and incentives
Some utilities and governments offer rebates for qualifying models, and the rules and amounts change frequently. If you plan to buy, check current local programs and the qualifying criteria before purchasing, since eligibility is often tied to specific rating levels.
Keeping expectations realistic
Efficiency gains on lighting are well understood and often easy to capture. Appliance savings are more modest per item, and larger gains usually come from heating and cooling. Even so, together they can make a measurable difference over a decade. Lower usage reduces both bills and the demand placed on the electricity supply, though the size of the effect on emissions depends on how the local electricity is generated.