How Many Lights Can I Install

There are a combination of factors that go into deciding how many lights you can install in a given space.

When designing your kitchen, you need to keep several factors in mind. To start, these facts should be kept in mind to make planning your lighting project easier:

  • A DC transformer or power supply only supplies power 20 feet in any one direction
  • Power supplies come in various wattages, usually from 6W - 60W, the amount of power they supply.
  • Every puck light, strip light, or tape light has a rating of how much power it draws, i.e., a 3W puck light or a 1.5W LED stick light

In the ideal setting, after knowing these facts, you will be able to, with a little basic math, design and plan your lighting for a given space. Planning how many lights to install also means planning how much power you need for your space.

Let's say one wall of your kitchen is filled with cabinets and is about 20' long. For simplicity sake, each cabinet is 12" wide. You want to place lighting under the cabinets to direct light down upon your cabinet tops but you don't know how many pucks or LED lighting strips you can install.

Power is supplied to our kitchens, for the most part, at 120V AC from our circuit box. (For more information about electricity, read our Basic Understanding of Electricity article.) To be safe and work efficiently with the lighting products, we use a DC power supply to reduce/transfrom that 120V AC to a safe 12V DC (direct current).

The Flow of Electricity in our Homes

As we already know, a 12V DC power supply supplies electricity 20' in one direction, so you can either install the power supply at one end of the wall of cabinets or in the center to provide up to 20' of power in each direction.

The Math Part

We know we have 20' of 12" cabinets and that means that we have about 20 cabinets...
20' at 12" per foot gives us 20 cabinets or 20' x 12" = 240" and 240"/12" = 20.

If we choose to install 3W puck lights and we want one light per cabinet, we would need 60W of power. Therefore, we would use a 60W power supply in our space to power 20 puck lights, or...

20 cabinets = 20 puck lights
20 puck lights X 3W power needed per puck = 60W of power needed.

Using this basic understanding of the power needs of the lights plus the power supplies available, we can plan our space accordingly.

Let look at the same example a different way... What is we decide we only want 1 puck light for every other cabinet? That would mean we'd only need (10) 3W puck lights.

Using our formula, 10 pucks X 3W power needed per puck = 30W of power needed. We could then use a 30W power supply to provide power to our 20' of cabinets at 1 puck light for every 2 cabinets.


In our last example, we want to use 1.5W LED Strip lights instead of pucks. We'll go back to the idea of having light under each cabinet. At 20 cabinets X 1.5W power per strip, we would still only need a 30W power supply... 20 x 1.5 = 30.


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