Understanding LED Light Bulbs
A Guide for Dummies
When I bought an LED light bulb for our living room, I was disappointed to find it far too “cool” in tone — an outcome of not fully understanding the “CCT” (Correlated Colour Temperature) parameter. This experience taught me how confusing the technical specifications on LED bulb packaging can be.
LED (Light Emitting Diode) light bulbs have become the preferred choice for energy-efficient lighting, but navigating their specifications can feel daunting. This article aims to simplify and clarify the key parameters you’ll encounter when choosing an LED bulb.
I’m going to the following as an example specification:
Wattage (W)
Wattage measures the amount of electrical power the bulb consumes.
In this case, the bulb uses 5 watts (W). Traditional incandescent bulbs often consume 40W or more for similar brightness. With LED bulbs, lower wattage equals reduced energy consumption, making them more cost-effective.
Lumen (lm)
Lumens indicate the brightness of the bulb.
This bulb produces 500 lumens (lm), which is suitable for ambient lighting in small rooms or task lighting in larger spaces. Higher lumen values, such as 800lm or 1000lm, indicate brighter bulbs suitable for larger or more illuminated areas.
Correlated Color Temperature (CCT)
Measured in Kelvin (K), CCT describes the color of the light emitted by the bulb. This bulb has a 3000K temperature, providing a warm white glow similar to traditional incandescent bulbs. Other common options include:
- 2700K: Very warm, cozy light for relaxation.
- 4000K: Cool white, suitable for kitchens or workspaces.
- 5000K+: Daylight or bluish-white light, ideal for task-oriented areas like offices or garages.
Colour Rendering Index (CRI)
CRI measures how accurately the bulb renders colours, on a scale from 0 to 100. A CRI of 80 means the bulb provides good colour accuracy for most purposes.
Higher CRI values (90 or above) are ideal for applications like photography, art, or makeup where true colour representation is critical.
Lifetime (T(h))
This bulb has a rated lifespan of 25,000 hours, meaning it can operate for approximately 10 years if used for 6–8 hours per day.
Longer lifespans are a hallmark of LED technology, outlasting incandescent and CFL bulbs.
Fy (Flicker Index)
The F50 refers to a flicker standard, which measures the amount of visible flickering in the light. LEDs are generally known for minimal flickering, but lower flicker values are preferable for sensitive environments like schools or offices.
Voltage and Frequency (V, Hz)
This bulb operates at 230 volts (V) and a frequency of 50 hertz (Hz). These values align with the power standards of many countries, including Sri Lanka.
Beam Angle
The beam angle of 230° indicates how widely the bulb distributes light. A 230° angle ensures even illumination for general lighting purposes.
Narrower angles (e.g., 30° or 60°) are better for spotlighting.
Base Type
The B22 base, also known as a bayonet cap, is commonly used in many countries. Other popular base types include:
- GU10: Common in spotlights.
- E27 (Edison screw): Widely used worldwide.
- E14: Smaller Edison screw base for decorative bulbs.
Dimensions (Size)
The dimensions of this bulb are 55mm in diameter and 99mm in height. Compact sizes are beneficial for fixtures with space constraints.
Current (mA)
The bulb requires a current of 30 milliamps (mA) to operate. This value is typical for low-power LED bulbs.
Why 30mA and not 21.7mA (5W / 230V)?
The discrepancy arises because LED bulbs are not purely resistive loads. They have electronic drivers that introduce a power factor (PF) less than 1, meaning the apparent power (voltage × current) is higher than the real power (5 W). For example, with a PF of 0.72, the apparent power would be around 6.94 VA, corresponding to a current of approximately 30 mA at 230 V. This accounts for the difference, as P/VP / VP/V assumes a PF of 1, which doesn’t apply to LED bulbs.
Dimmability
This bulb is not dimmable, meaning it cannot be used with dimmer switches. If you need adjustable lighting, look for bulbs labelled as “dimmable.”
Lumen Maintenance
The bulb maintains 95% brightness after 1000 hours of use. This indicates excellent durability and light consistency, essential for long-term usage.
This would also imply that after 10,000 hours of use, the bulb would maintain about 60% brightness.
