Testing by MyBroadband confirmed that LED bulbs have the best efficiency, followed by compact fluorescent light bulbs (CFLs), and incandescent bulbs.

To see which light bulbs are the most efficient, MyBroadband tested the power draw and light output for widely available bulbs.

To measure the power draw, MyBroadband used a PZEM-004T based monitoring system to see how they compare with the rated values.

The measurement module measures AC voltage, current, real power, frequency, and power factor with an accuracy of better than 1%.

We then compared the power draw with the light emitted by each bulb, measured in luminous flux, to get an efficiency measurement.

Luminous flux is a measure of the total light emitted by a source and is often used as a point of comparison between different lights, usually indicated on light bulb packaging in lumen (lm).

Luminous flux can be difficult to measure precisely, as all the light in all directions from the source needs to be captured.

Illuminance, measured in lux (lx), is the intensity of light over a surface area and is much easier to measure.

If only one square metre of a surface is lit up by a 1-lumen source, then the brightness will be 1 lux.

By making some assumptions about the distribution of light, lumens can be calculated from a lux measurement.

If one assumes that a light bulb is equally bright in all directions (which is not entirely true), the lumens can be calculated from a spherical surface area based on the distance of the lux measurement.

The error from this assumption can be reduced by taking measurements from different directions relative to the light bulb and averaging these values.

For comparison between light bulbs, MyBroadband took measurements with the light bulb inside a large cardboard box to reduce the influence from other sources.

Only a small gap in the box was opened to allow for the measurement to be taken using a lux meter built into a smartphone.

While this is not a calibrated instrument, it should suffice for this experiment.

Nine measurements were taken from the side, bottom, and top of each bulb. The average for each location was then calculated.

To get to a final lumen value, the averages were weighed 4:1:1 for the sides, top and bottom, to get an estimate of the total luminous flux all around the bulb.

These values were then normalized against the advertised lumens for each bulb.

Although this method is not perfect, the estimated luminous flux still provides a comparable value between light bulbs as all the same assumptions have been made for the different bulbs.

The tests revealed that LED and incandescent bulbs get up to a consistent and final brightness very quickly after being switched on.

CFL bulbs, in comparison, slowly increase in brightness over around a minute after being first switched on.

CFL and incandescent bulbs take some time to stabilise with regards to power draw, while LED bulbs immediately draw power consistently after being switched on.

To account for these differences, each bulb was on for around 2 minutes before taking any measurements.

The results revealed big differences in efficiency between LED, CFL, and incandescent bulbs.

The LED globes had the best average efficiency at 96 lm/W, with CFL bulbs coming in at 58 lm/W, and incandescent bulbs only achieving 9 lm/W.

This is in line with what has been published about the average efficiency of these types of bulbs.

Another interesting point is that both LED bulbs and 75% of the CFL bulbs were measured to have higher luminous flux than advertised.

Both incandescent bulbs in the test measured lower than advertised values using our methodology.

The table below provides an overview of the results of our light bulb testing.

Compact fluorescent lamp (CFL) Headline LED light bulb

Comments section policy: MyBroadband has a new article comments policy which aims to encourage constructive discussions. To get your comments published, make sure it is civil and adds value to the discussion.

Which brand of fridge do you have at home?