COB Lights Versus Incandescent Lights

Electromechanical Optoelectronics
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We are often asked what the power consumption of our Chip on Board LEDs is. This post will cover an explanation of how one can determine how many watts these lights consume on average. Also, for reference, I will talk about comparing to the older technology (incandescent) as it may be useful information.

See also for more context on calculating wattage

Incandescent vs. LED: Comparing Ratings

COB lights list more parameters in their datasheets than the older technology used to list on the product box. In the older fluorescent fixtures and incandescent models, most were rated with voltage, current, and power consumption (wattage). These fixtures didn’t have many active components to start with (if any) and the technology didn’t need complex terminology. When LEDs were developed, an equivalent rating had to be developed for analogy because the devices draw way less than the older technology. When I used to work in a department store, there were ratings typically saying that around an 8.5W LED is nearly equivalent to a 60W incandescent bulb in most cases after comparing brightness/luminosity. So in that case, a 60W COB is like a 424W incandescent bulb when comparing how much power is consumed! Many stores will have this type of comparison for analogy, but does not always hold constant. It is always recommended to read all the data available for the chips because wattage does not equal brightness.

COB Wattage Calculation

To find the average power consumption that the chip will use. It is up to the individual to choose a driving current for the application. Typically, manufacturers include both a testing current and maximum current to help provide guidelines. It is never recommended to run any device at or very near maximum current because this will reduce the life of the LED significantly. Read the data sheet for the specific part to see why the manufacturer included a testing current, this may be the nominal current to choose for maximum efficiency.

P_{Test}=I_{Test}*V_{forward}
P_{Max}=I_{Max}*V_{forward}

In reality, the power drawn by the component will not be constant because there are more factors like heat dissipation, operating temperature, operating conditions, and even design of the surrounding circuitry can change the power values. These calculations are for a reference as the driving current will heavily impact the amount of power drawn.

Comparison to Incandescent

To do a rough comparison to an incandescent bulb for reference:

\frac{8.5W}{60W}\approx\frac{P_{Led}}{P_{Inc}}

The PLed can be calculated from PTest, PMax, or using your own driving current to find power. The only unknown variable is PInc which is what would be solved for. This will not be an exact estimate as more factors go into equivalencies, but should give a rough idea compared to incandescent.

Otherwise, compare ratings and values found in the data sheets to other similar product’s data sheet values.

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One should also note that unlike incandescent bulbs, the wattage value one derives for an LED light source such as a COB does not necessarily correspond to a brightness value. A higher-wattage LED might not necessarily be brighter than a lower-wattage one, and double the wattage does not mean double the brightness or vice-versa. Wattage figures for LEDs should generally be used to calculate the power requirements for your device, not used as a means of brightness comparison as is the case for incandescents.

EDIT: To clarify as per Kaleb’s comment below, I’d meant to state that two 60W LED devices would not necessarily have similar brightness levels, rather than a 60W LED and a 60W incandescent. Wattage on an LED device has little to do with its luminous performance; one shouldn’t assume that one COB which draws 60W of power will perform the same as another COB which also coincidentally draws 60W of power, unlike the assumption that one 60W incandescent bulb is pretty much the same as any other.

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Matt is correct, not all 60W LEDs will be brighter than their incandescent counter-parts, but many times it is generally true. If my assumption is not turning out valid, then the luminosity values will matter.