How to Plan Power Supply Capacity for 10m and 20m COB LED Strips

To plan power supply capacity for a 10m or 20m COB LED strip, multiply the strip’s rated power per meter by the installed length, then add a practical capacity margin. For example, a 24V strip rated at 10W/m uses 100W over 10m and 200W over 20m; allowing 25% headroom gives minimum supply capacities of 125W and 250W, respectively. These figures are examples, not specifications for every COB strip: always use the product’s actual voltage and wattage rating. For long runs, also plan how power will be fed along the strip, because a correctly sized supply does not by itself prevent voltage drop or uneven brightness.

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Power Supply Planning: Key Takeaways

• Calculate total load from the strip’s rated watts per meter and the length you will actually install.
• Choose a compatible constant-voltage supply, such as 12V or 24V, to match the strip’s label and datasheet.
• Allow headroom, then check the supply’s continuous output rating and any manufacturer derating guidance.
• For 10m and especially 20m installations, confirm the strip’s maximum feed length and plan suitable power-injection points.
• Request the product datasheet and a wiring recommendation before finalizing a B2B project order.

Step 1: Confirm the Strip’s Electrical Specifications

Start with the exact COB LED strip model, not a general assumption based on its length or appearance. Check its rated input voltage, power consumption in watts per meter, maximum recommended run length, and whether the product is designed for constant-voltage operation. COB describes the LED arrangement; it does not establish the strip’s voltage or power consumption.

Also check whether the wattage applies to the full strip and whether the stated value is nominal or a maximum. A 10m reel and a 20m installation can have very different loads if the selected strips have different power ratings. If you are comparing models, use each model’s own datasheet rather than applying one calculation to the whole COB category.

Why voltage matters

The power supply output voltage must match the strip’s rated voltage. For the same electrical power, a lower-voltage system draws more current, which can affect cable selection, connections, and voltage drop. Never use a higher-voltage supply on a strip unless the product documentation specifically allows it.

Step 2: Calculate the Total Load

Use this formula for a single strip or a group of strips connected to the same supply:

Total strip load (W) = rated power per meter (W/m) × installed length (m)

Then estimate the current required at the strip’s rated voltage:

Current (A) = total load (W) ÷ supply voltage (V)

These calculations give you a starting point for selecting a power supply. They do not replace the manufacturer’s instructions on maximum run length, wiring, or supply operation.

Worked examples for 10m and 20m

Assume, for illustration, that a COB strip is rated at 10W/m and 24V. A 10m installation has a calculated load of 100W, or approximately 4.17A at 24V. A 20m installation has a load of 200W, or approximately 8.33A at 24V.

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If you use a planning margin of 25%, the corresponding supply capacities are 125W for the 10m load and 250W for the 20m load. The 25% margin is a practical example rather than a universal rule; confirm the supply’s continuous output rating and the manufacturer’s recommendations for your operating environment. If the strip is rated at 12V instead, the same 100W load draws approximately 8.33A, so current and wiring requirements change even though the wattage is unchanged.

Step 3: Plan Power Distribution for Long Runs

A power supply can have enough total wattage while the far end of a long strip still receives less voltage than the near end. This can lead to visible brightness differences, depending on the strip, layout, wiring, and load. The solution is not simply to buy a larger-wattage supply: distribution and feed points must also be considered.

Check the COB strip datasheet for its maximum recommended continuous length and power-feed guidance. Depending on the product and installation, options may include feeding the strip from both ends, adding power at intermediate points, or dividing the run into shorter sections with separate feeds. Any injection wiring must use the correct voltage and polarity, and the total connected load must remain within the supply and wiring ratings.

Consider one supply or multiple supplies

A single supply may suit a project when its output capacity, wiring distance, and distribution plan are appropriate. Multiple supplies can make sense when the installation is divided into separate zones or when cable routes and strip limits make one feed inconvenient. If using multiple supplies, follow the product and supply manufacturers’ connection instructions, and do not connect outputs in parallel unless they are specifically designed for that use.

Step 4: Check the Power Supply and Installation Conditions

Compare the calculated load with the supply’s continuous output rating, not just a peak or short-duration figure. Check the input voltage, output voltage, dimming compatibility if needed, enclosure and mounting requirements, and the manufacturer’s operating-temperature guidance. Some supplies require output derating under particular conditions, so the usable capacity may be lower than the headline rating.

Review the full installation as a system: strip, supply, cables, connectors, controller, and protection devices. A dimmer or controller must be compatible with the strip voltage and capable of handling the connected load and current. For commercial indoor lighting projects, confirm the applicable electrical requirements with the project’s qualified installer or electrical professional.

Common Power Planning Mistakes

• Choosing by length alone: Two 20m COB strips may require different supply capacities if their W/m ratings differ.
• Ignoring voltage: The same wattage draws different current at 12V and 24V, affecting cable and connection planning.
• Assuming extra wattage fixes voltage drop: Supply capacity and power distribution are separate design considerations.
• Using a supply with the wrong output voltage: Match the supply to the strip’s stated input voltage.
• Skipping system checks: Controllers, connectors, wiring, and installation conditions must all suit the load.

How ENTA Lighting Can Support Your Selection

At ENTA Lighting, we recommend beginning with the strip model and installation plan rather than selecting a power supply from length alone. For a 10m or 20m COB LED strip requirement, share the rated voltage, watts per meter, number of runs, intended control method, and approximate cable route with our team. These details help us review the load calculation and identify product-specific questions, including maximum run length and power-feed arrangements.

For project procurement, request the relevant datasheet and confirm the supply requirements before placing an order. This is especially useful when the project includes several strip lengths, different brightness requirements, or a long cable route between the supply and the lighting. Final installation and electrical protection should be verified by a qualified professional for the project location.

Conclusion: Size the Supply and the Feed Plan Together

To plan power supply capacity for 10m and 20m COB LED strips, multiply the actual rated watts per meter by the installed length, divide by the strip voltage to estimate current, and select a compatible supply with appropriate headroom. In the 10W/m, 24V example, 10m requires 100W of strip load and 20m requires 200W; an illustrative 25% margin leads to 125W and 250W supply capacities. Treat these as calculation examples, not universal product recommendations.

Your next step is to confirm the exact strip datasheet, maximum feed length, and supply derating guidance, then plan wiring and injection points for the installation. Send ENTA Lighting your strip specifications and project layout to discuss a suitable COB strip and power-planning approach for your indoor lighting requirement.