FAQ - LED and Incandescent Equivalency

Many LED lighting products are sold advertising an equivalence to incandescent lights of various wattages. As there is currently no MEPS (Minimum Energy Performance Standard) specified for LED lighting and the performance differences between LED lights and common incandescent globes are not common knowledge, these claims often fall short of customer expectations. Many performance factors determine the feasibility of an LED product as a "direct replacement" for a legacy lighting product such as an incandescent or halogen globe. The lumen output, light distribution, colour quality, degree of flicker and system compatibility of a product all must be considered for suitability in a given application.

Lumen output

Products claiming to be direct replacements for an incandescent of a certain wattage can often produce light levels well below the typical performance of the claimed equivalent. Even when a manufacturer's light output claims are accurate, the number of lumens may not be consistent with the incandescent wattage it is recommended to replace. As a guide, the minimum lumen output for incandescent equivalence claims specified by ENERGY STAR® in their Program Requirements for Integral LED Lamps document is included below:

Nominal wattage of lamp to be replaced (watts)	Minimum initial light output of LED lamp (lumens)
25	200
35	325
40	450
60	800
75	1,100
100	1,600
125	2,000
150	2,600

Light Distribution

Unlike incandescents and halogens, which emit light about all directions of the filament, LED light sources are naturally directional. The light distribution for similarly shaped globes can thus turn out markedly different from each other. Many retrofit globes like the Philips LPRIZE-PRO or FEIT's A19 Omni deliberately emulate the spatial light distribution of incandescent globes, however others that look physically similar, like CREE's 9W Globe may give markedly different light spreads. The below figure illustrates the vastly different light distribution patterns of various A19 LED globes in comparison to an incandescent. The globes pictured, from left to right, are a Philips 60 W incandescent, a Philips 10W A19 LPRIZE-PRO, a FEIT A19 Omni LED globe and a Philips 13W Globe.

Light distributions of A19 incandescent and LED globes While users may be accustomed to the light spread of traditional lighting, often an exact replication of the incandescent's characteristics is not necessary and the difference may even better suit the user's application. The light distribution pattern on the far right for example may better suit focused task lighting. Other applications might not. Vertical ceiling fittings, for example, were designed around incandescent globes, the light emitted upward from an omnidirectional light would be reflected by a white ceiling, improving the perceived brightness of the room. Ceiling light fixtures where a globe must be horizontally mounted, such as oyster lights etc, were designed for omni-directional light sources; a globe with a light pattern like the Philips 13 W globe above would thus result in an unevenly lit room.

Colour Quality

The colour temperature and Colour Rendering Index of a light source determine the appearance of the light and the objects being illuminated. Incandescent bulbs generally generate a yellowish "warm white" colour with a CCT of around 2700K and a CRI of 100 (as incandescents are the reference light source used in the CRI metric). LED lights offer a much broader range of colour temperatures, ranging from warm white to natural (sometime's called 'pure' or 'daylight') white to a bluish cool white. Different colour temperatures may suit different spaces and tastes. In general, warm white may be a more appealing choice for spaces with lower levels of light while pure and cool white lighting tends to complement spaces with high levels of light or sunlight.

Flicker

As was stated in our FAQ article about flicker, some LED lights can exhibit more dramatic flicker than in conventional light sources, however it is by no means a characteristic of all LED lighting and tends to occur in lower quality, cheaper LED lighting products. Individuals who want a degree of flicker less than or equal to that of incandescents should use LED lamps with a maximum percent flicker of 10% on 50 Hz mains or a maximum of 14% on 60 Hz mains.

System Compatibility

Purchasing a suitable replacement for a traditional light source such as an incandescent or a halogen requires knowledge about the system it is expected to operate in. If the light is to be installed in a dimming circuit, the user must ensure that the LED replacement globe is compatible with either leading or trailing edge dimmers, depending on your dimmer. Many LED globes are stated as unsuitable for enclosed light fixtures because they require air circulation for proper thermal management, consequently ruling them out as options for many replacements.

12 VAC MR16 halogens can be replaced with retrofit LED downlights and used with existing 12 VAC electronic transformers, however most (if not all) LED MR16 retrofits cannot claim universal compatibility with all 12 VAC electronic transformers. If a transformer not explicitly recommended by the LED manufacturer is used, performance of the LED light may suffer, lead to early failure or even not work at all. This compatibility issue was explored in our FAQ article 12V Transformers and LED Compatibility.

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