Adding under cabinet lighting is an excellent functional upgrade for your kitchen. My configuration may not work for your particular situation but hopefully this post will give you ideas.
Running the wires takes a little planning, if you have high quality cabinets it will be a little more difficult because its unlikely you will have gaps and hidden spaces to run wires. For the time being my house has off the shelf big box cabinets that have plenty of spaces for wires and I don’t feel too bad about drilling holes in them. Please note that you should only run low voltage wires in this manner.
I ran the wires down the gap between two cabinets. The wires are routed through plastic wire channel available at any big box home store, the switch and surface mount box can be found in the same department. Note that I am switching the low voltage 12VDC not line voltage. In this photo you can see the LED puck lights, there are 3x 1Watt LED’s in each light, they are rated at 240 lumens per fixture. These lights as listed as Warm White, I estimate the color temperature at about 3000k, they are slightly cooler than the 2700k LED retrofits in the ceiling.
If you don’t have space for a surface mount switch you can use a remote controlled switch such as this.
You will need a decent quality “LED Driver” which is really nothing more than a transformer that will turn your line voltage (120VAC) into 12VDC. If you need dimming functionality you will have to take several factors into consideration. Some LED fixtures such as the LED pucks I choose include a bridge diode (bridge rectifier), these types of fixtures are identifiable by the fact that they are not sensitive to polarity. Any non-bridged LED will be sensitive to polarity. Because of this bridge these LED’s will not dim with a PWM dimmer. If your LED’s do not have a bridge you can dim them with a $5 PWM controller. The best way to dim a bridged LED fixture is to use a magnetic transformer and a dimmer switch on the line voltage side of the circuit. Size your transformer based on the current draw of your lights. I chose the 80 watt transformer because I will likely add a LED strand on top of the cabinets as accent lighting.
I wired the low voltage side into a fuse block for easy distribution. I put the transformer into the cabinet above the microwave since I never put anything in there. Even though I have the under cabinet switch I also used one of the RF controlled outlets so I can control the lights with a remote.
On the low voltage side I used a bus topology that is run across the entire width of the cabinets. Each light then has a small wire (about 22ga) that is then soldered onto the bus. Between cabinets I drilled holes and pushed the wires through. I chose 14ga wire though I should have used a 12ga minimum because I’m getting about a .5v drop by the end of the 14ft run. I should have done the math on this but I figured at 3.5 amps the 14ga would have been sufficient. I had to stop here for the time being because I ran out of puck lights, another pack of 10 are in the mail so I can do the other side of the kitchen. These particular puck lights are also available in daylight at 6000k.
Detail on the plastic wire conduit. Its a 1″ width. If I had to do it again I would go the next size up, it starts to get very tight inside when including the plastic connectors that come pre-installed on the puck lights. I cut them to width using a stanley miter box.
I added a LED strip above the cabinets as accent lighting, turned out pretty good. The above cabinet lights + under cabinet are drawing 72 watts and provide more than enough light to work by.
Link to the strip and remote control
LED Strip on Amazon
RF LED controller
Parts list for my install.