LED power consumption: what your light really costs per year

The formula: watts times hours, divided by 1000, times electricity price

Hardly any question about lighting can be answered as cleanly as the one about running costs. You need just three numbers: the power consumption of the light bulb in watts, the burning time in hours and your electricity price per kilowatt hour. The formula is: watts times hours, divided by 1000, gives the consumption in kilowatt hours. Multiplied by the electricity price, the result is the amount in euros. You find the wattage on the packaging or directly on the cap of the light bulb, and the unit rate on your last electricity bill.

For all worked examples in this article we assume an electricity price of 35 cents per kilowatt hour. This is a deliberately chosen assumption in the range of typical household tariffs, not a measured value and not a current market price: your actual unit rate may be lower or higher. If you pay about 30 cents, subtract roughly one seventh from our results; at 40 cents, add the same amount accordingly. The ratios between incandescent, halogen and LED are not affected.

A warm-up example: an LED of 9 watts burns for three hours. That is 9 times 3, equal to 27 watt hours, or 0.027 kilowatt hours. At 35 cents per kilowatt hour, this evening costs less than one cent. That is exactly why the LED has taken the heat out of the discussion about lighting costs: with modern light bulbs, it is no longer the single hour that counts but the sum of many lamps and many years.

Worked example: a 9 watt LED in everyday use

Let us work through a realistic year. An LED of 9 watts, for example as a replacement for the classic 60 watt incandescent bulb, burns for four hours a day on average: in the morning in the bathroom, in the evening in the living room. That gives 9 watts times 1460 hours, or about 13.1 kilowatt hours a year. At our assumed electricity price of 35 cents per kilowatt hour, that is about 4.60 euros. A more economical 8.5 watt LED comes to about 4.35 euros. For comparison: the 60 watt incandescent bulb would come to 87.6 kilowatt hours with identical use, and so to about 30.70 euros.

Important for putting this in context: what determines brightness is not the wattage but the lumen value. A good LED delivers the 806 lumens of the old 60 watt bulb with about 8 to 9 watts. If you only look at watts when buying new, you are comparing apples with pears. Which lumen figure corresponds to which old wattage class is shown at a glance by our lumens-to-watts chart; it is the matching tool for all the calculations here.

Comparison table: incandescent, halogen and LED over a year

The following table runs three brightness classes across all technologies. Assumptions: four hours of light a day, 365 days, assumed electricity price 35 cents per kilowatt hour, values rounded:

From warm white to daylight white: the kelvin figure changes the mood of your light, not the consumption. So you never have to economise on colour temperature.

The pattern is clear: for the same brightness, the LED needs roughly one seventh of the electricity of an incandescent bulb and about one fifth of a halogen light bulb. For a single lamp that sounds like small change, but for a household with 15 to 25 light bulbs over several years it adds up to a three-figure amount. That is exactly why it is worth looking at every single lamp holder.

When replacing really pays off

The short answer: almost always, as soon as the lamp burns regularly. In our worked example, an LED of the 806 lumen class saves a good 26 euros a year compared with the 60 watt incandescent bulb, and about 17 euros compared with the 42 watt halogen light bulb. Since branded LEDs for E27 and E14 in the entry-level to mid-range price bands cost only a few euros, the purchase price is typically earned back within a few weeks to months at four hours of burning time a day. After that the lamp keeps saving every year, over a rated lifetime that manufacturers usually state as 15,000 hours and more.

There is also an honest reality check: in lamps that run only a few minutes a week, for example in a storeroom or in the loft, consumption hardly matters. There you can happily keep running a working old light bulb until it fails. The priority goes to the lamps that are always on: living room, kitchen, hallway and the desk. Which LED belongs in which cap, and what to look out for with E27, GU10 and E14, is explained in our guide to LED light bulbs.

An often overlooked item is the light around the house: path lights and façade lamps with a dusk-to-dawn sensor quickly run for six to twelve hours a night, and so for clearly more hours a year than any living room lamp. This is where the LED pays off fastest, in every season. You can find suitable options, from wall lights to spotlights with a PIR motion sensor, in our overview of outdoor lighting.

Smart lamps and standby: honestly calculated

Smart light bulbs have a property that appears in hardly any brochure: they are never fully off. So that the lamp can respond to an app, a voice command or a routine, its radio module stays permanently ready to receive and typically draws about 0.2 to 0.5 watts while doing so. Over a year that is roughly 1.8 to 4.4 kilowatt hours per lamp, so about 60 cents to 1.50 euros at our assumed electricity price. For a single lamp that is bearable; with 15 to 20 smart light bulbs in the household, though, a good 10 to 25 euros a year can add up, without a single hour of light.

Honestly, the balance is still usually positive: if you use smart lamps for routines, presence simulation or precise dimming, you often win the standby back through the burning time saved. It is only important to know the effect. If you cut a smart lamp completely from the power at the wall switch, you save the standby but lose reachability by app and routine; the lamp is then simply offline until the next time it is switched on. What smart systems from Hue to Matter can do in everyday use and where their limits lie is shown in our buying guide to smart lighting.

Dimming, colour temperature and consumption

With LEDs, dimming is a real way to save, not a placebo. If you reduce the brightness, the power consumption falls too, roughly in line with the level set. A lamp dimmed to half does not use exactly half because of losses in the driver, but noticeably less than at full output. If you prefer to sit in subdued, warm light in the evening anyway, you get the saving for free. The prerequisite is a dimmable light bulb and a matching dimmer switch; non-dimmable LEDs respond to the attempt with flickering or early failure.

For colour temperature, by contrast, there is an all-clear: whether you choose 2700 kelvin warm white or 6500 kelvin daylight white makes no noteworthy difference to consumption. The kelvin figure describes the hue of the light, not its power consumption. So you can plan your lighting mood freely by room and time of day without worrying about the electricity bill. You gain more efficiency instead through the right brightness: a room that is comfortably lit with 400 lumens does not need a 1500 lumen lamp running all the time.

Conclusion: small watts, small bill

LED light is so cheap to run that the question of running costs almost always comes out in favour of the light. In our worked example a single LED costs a few euros a year, replacing old incandescent and halogen lamps pays for itself within months in frequently used lamps, and even the standby of smart lamps stays manageable as long as you know about it. The order for savers: first replace the lamps that are always on, then the outdoor lighting, and the rarely used lamps last. How much light your rooms need at all is quickest to work out with our lighting calculator; more basics from lumens to colour temperature are collected in our guides section.