Cost of Low-Voltage Lighting

How much does it cost to run my low-voltage lighting system?

This is a question we get asked quite often, so why not write a blog about it?  So, how much will your electricity bill go up with a new outdoor lighting system?  There are a lot of factors that go into this cost, but I will try to make it as simple as I can.

Transformer

The transformer converts the 120-volt power coming out of the outlet down to 12-volt power.  It is a 10-to-1 conversion, 120 volts in down to 12 volts out.  Why do we use 12 volts for landscape lighting?  Running 12-volt power throughout your yard is safer and less costly than running 120-volt power.  It is also easier to move a light fixture when a tree dies, or a bush gets bigger because 12-volt wires can be directly buried in the dirt as opposed to running the wires in conduit for 120-volt.

Each transformer will have a rating of how many watts can be powered from each unit.  We usually use a minimum size transformer of 300 watts for our installation now with LED lamps.  When I first started installing landscape lighting, back in the late 1990’s we would use 1200-watt transformers quite often. Halogen and incandescent lamps took a lot more power than LEDs do now.   The first number we will need is the power rating of the transformer and how many transformers are in the yard.  

How long are your lights on at night?  

The next number we will need is how long do you keep the lights on at night.  All our transformers are equipped with an astronomical timer to tell the lights when to turn on.  The astronomical timer knows when the sun sets every day.  In the winter, the lights may turn on by 4 pm, and in the summer they may not turn on until 9 pm.  If you have your lights turned off at midnight, that means the lights will be on for 8 hours in the winter and 3 hours in the summer.  That is an average of 5.5 hours per day.  This is the second number you will need for the equation.

Kilowatt-hour 

How much are you paying for an average kilowatt hour?  You can look this number up on your monthly utility bills.  For our southeast Wisconsin clients, this number is about 0.1372 cents, and for our northern Illinois clients, it is about 0.1418 cents.  

What do you do with these numbers?

If you search the internet for an energy use calculator, you will find a site that will do the math for you.  If you put in 300 watts for 5.5 hours per day and a kwh cost of 0.1372, the light electricity will cost you $6.88 per month.  For my friends down in Illinois, put in the 0.1418 for the kwh and it comes out to $7.12 per month.  As you can see electricity will cost you about as much as one cup of coffee per month.  Think of the joy you are receiving from being able to enjoy your home and garden after the sun goes down.  Please set up a time to meet with one of our designers for your custom lighting plan here. We’d be happy to help!

Light On!

Mike Long