Watts, lumens, and colour on one label
The U.S. Department of Energy explains that lumens describe light output while watts describe power input; comparing wattage alone does not tell you how bright a lamp will appear. The same source notes colour appearance values such as 2700K described as warm and 3000K described as soft, and stresses that colour appearance is not wattage. Read all three lines together: output for brightness, power for energy, and kelvin for the tone of the light.
| Label line | What it tells you |
|---|---|
| Lumens | Light output |
| Watts | Power input |
| Kelvin (K) | Colour appearance, e.g. 2700K warm, 3000K soft |
Worked annual energy example
Two 11 W lamps running 3 hours a day for 365 days at a rate of 0.2 per kilowatt-hour produce the totals below. Multiply watts by count, then by hours and days, divide by 1000 to reach kilowatt-hours, and multiply by the rate for cost. Your own rate and schedule will change the result.
| Input or result | Value |
|---|---|
| Lamp power | 11 W |
| Lamp count | 2 |
| Hours per day | 3 |
| Days | 365 |
| Annual energy | 24.09 kWh |
| Annual cost | 4.818 |
| Displayed annual cost | 4.82 |
Match the lamp to the task in the room
A reading corner and a general ceiling fill need different outputs, so check the lumen figure rather than swapping one wattage for another. Note where glare lands at eye level and whether the colour tone suits the wall colour you already have. These are choices you make in your own room; the label supplies the numbers, and this page supplies the arithmetic.
Does higher wattage mean more light?
No. Lumens measure light output and watts measure power input, so two lamps with the same wattage can differ in brightness.
Is the energy figure a saving claim?
No. It is a multiplication of your own inputs: watts, count, hours, days, and rate. No comparison, price, or saving is implied.
What does 2700K mean?
The Department of Energy source describes 2700K as warm and 3000K as soft. Kelvin describes colour appearance, not brightness or power.