True Watts vs. Advertised Watts, LED grow light wattage

LED grow lights have revolutionized indoor gardening by providing efficient and customizable lighting solutions for plants. When considering LED grow lights, one important aspect to understand is the wattage and how it relates to the light's actual power consumption. However, it's not uncommon to find a difference between the advertised wattage and the true wattage of LED grow lights. This disparity can often lead to confusion among growers who are seeking accurate information to make informed decisions.

In this article, we will delve into the concept of LED grow light wattage and explore the reasons behind the differences between advertised wattage and true wattage. By understanding these factors, growers can gain valuable insights into how wattage affects plant growth, energy efficiency, and overall performance, enabling them to make more informed choices when selecting LED grow lights for their indoor gardening endeavors.

True Watts and Advertised Watts

A green wattage: how much energy consumed

In the realm of LED grow lights, two terms often come into play: true watts and advertised watts. The difference between these two measurements can stem from various factors. Therefore, understanding the distinction between true watts and advertised watts is crucial for growers to assess the light's performance and their investment.

Manufacturer's Wattage Rating

When purchasing LED grow lights, manufacturers typically provide a wattage rating for their products. This rating serves as a guideline for growers to assess the light's power output and determine its suitability for their specific indoor gardening needs. However, it is important to note that the manufacturer's wattage rating is an advertised value that may not always reflect the actual power consumption of the LED grow light.

Factors such as internal electronics, driver efficiency, input voltage changes, and other technical aspects can contribute to variations between the advertised wattage and the true wattage of the light fixture. These factors lead to two different terms that are used by manufacturers as advertised watts: "LED Watts" and "Draw from the Wall".


LED watts refer to the maximum potential power that the LEDs can handle. Many companies selling LED grow lights only use LED watts to advertise their lights, as the number is always larger and more impressive than the actual true watts. In general, 30-50% less wattage is needed for LED grow lights compared to traditional grow lights, depending on the efficiency of the LED grow light.


The term "draw from the wall" is commonly seen in the discussion of growers, which refers to the total power consumption of the LED grow light system, including not only the power used by the light fixture itself but also any additional power consumed by external components such as drivers, fans, or other supplementary devices connected to the light. It represents the power drawn from the electrical outlet to operate the entire LED grow light system, and it may also be named as the "Input Power Draw".

The Concept Of True Wattage

The true wattage of LED grow lights refers to the actual power consumption of the light fixture. It refers to the electrical power consumed by the light fixture to produce light. True watts are specific to the LED grow light and indicate the energy usage directly attributed to the light's operation.

It's important to note that the draw from the wall typically includes additional components and losses in the electrical system, such as power conversion losses or inefficiencies. Therefore, the draw from the wall may be higher than the true wattage of the LED grow light alone.

Why The True Wattage Is Different From The Advertised?

Plugs in the socket to draw power for appliance

The true wattage of an LED grow light represents the actual power consumed by the light fixture to produce light. In contrast, the advertised watts can refer to either the "LED watts," which represents the maximum power handling capacity of the LED, or the "Draw From The Wall," which encompasses the total power consumption of the entire light fixture. Due to these different measurements, it is expected to observe variations between the true watts and the advertised watts. The detailed reasons behind these differences are as follows:

Internal Electronic Consumption

LED grow lights often have internal electronics such as drivers, transformers, or control circuitry that facilitate their operation. These components can consume some amount of power themselves, resulting in a difference between True Watts and Advertised Watts.

While this energy consumption is not directly contributing to light production, it is necessary for the proper functioning of the LED grow light. It contributes to the overall power consumption of the LED grow light, which is encompassed in the "Draw From The Wall" measurement and is typically advertised by manufacturers.

The Diver Efficiency and Diode Handling Power Draw

LED grow lights rely on drivers to convert the incoming electrical power into a form that is suitable for the LEDs. However, the efficiency of these drivers can vary, with some drivers being more efficient than others. A less efficient driver can contribute to a higher difference between the advertised wattage and the true wattage of the LED grow light. This is because a portion of the electrical power may be lost as heat or in the conversion process, resulting in a lower actual power output.

Additionally, the individual diodes used in LED grow lights can have different wattage ratings. These ratings, known as "LED Watts," are often provided by the diode manufacturers and represent the maximum power output achievable by the diodes under optimal conditions and peak performance. Some LED grow light manufacturers may use these diode wattage ratings to exaggerate the potential of their fixtures, even though the actual power consumption and performance may differ in real-world applications.

Measurement Tool Deviation

The wattage rating provided by manufacturers is often an approximation or a rounded value. Variations in the manufacturing process and measurement tolerances can contribute to differences between the advertised and true wattage. Also, differences in the measuring instruments used can cause some degree of error values. When the two errors are superimposed, the measurement error can be far from the true value.

Power Losses

During the conversion of electrical power within the LED grow light, there can be inherent power losses due to heat dissipation or electrical inefficiencies, which should be included in the "Draw From The Wall". These losses can result in a lower true wattage compared to the advertised wattage.

Input Voltage Difference

The wattage output of an LED grow light can be influenced by the voltage it operates on. Volts and amps requirements are inversely proportional, meaning that as voltage increases, amperage decreases.

Consequently, when the input voltage is higher, the current running through the LED grow light will be lower, resulting in lower heat generation and reduced circuit consumption. This, in turn, leads to a lower "draw from the wall" in terms of power consumption. Therefore, it is true that using a higher input voltage to operate LED grow lights can potentially save electricity. But be sure to apply the input voltage within the manufacturers' given ranges.

The Impact Of Wattage Difference

A light bulb in the hand actual watts

Does It Affect The Light Output?

Yes, it does. The true wattage directly affects the amount of electrical power available to generate light. A higher true wattage generally correlates with higher light output, as more power is allocated to the LEDs. It is the efficiency metrics.

However, when it comes to the efficiency of led grow lights, the light efficacy (measured in μmol/J) is more commonly used to provide a measure of how effectively the LED grow light converts electrical power into usable light for plant growth.

Does It Affect The Plant Growth and Yield?

Not necessarily. The wattage of LED grow lights does not have a direct impact on plant growth and yield. Instead, it is the PPFD (Photosynthetic Photon Flux Density) values that play a crucial role. Therefore, if you are concerned about the light quality and quantity necessary for growing plants, the difference between the true wattage and advertised wattage is not a primary concern. Instead, focusing on the PPFD chart provided by the vendors is the best approach to assess the light output's quality and suitability for your plants.

The PPFD chart provides information about the intensity of light (PPFD numbers) and the pattern of light distribution (PPFD pattern). These metrics are more relevant to understanding how well the LED grow light will meet the specific light requirements of your plants. By examining the PPFD values and uniformity, you can evaluate the light output's effectiveness in providing adequate light energy for photosynthesis and promoting optimal plant growth.

Does It Affect The Measure of Energy Consumption?

No, it doesn't. The wattage difference between the true wattage and advertised wattage does not affect the measurement of energy consumption. When it comes to understanding how much electricity is used to operate your LED grow lights, the metric you should consider is the "Draw From The Wall." This measurement reflects the actual energy consumed by the light fixtures when they are running.

To Round Up

Assessing the specific needs of your plants, understanding the advertised wattage and true wattage, and considering additional factors like light quality and energy consumption will help you make informed decisions when selecting LED grow lights for your cultivation needs. Hope this blog can help you understand "True Watts", "LED Watts", "Draw From The Wall" and "Advertised Watts"!