GETTING LIT: PART II – A COST EVALUATION OF LANDSCAPE LIGHTING

January 26, 2012: So how much does it cost to run a home’s landscape lighting system? Well, that depends on the home and the system size. Before I set out on my mind numbing math calculations, I’ll need to set up the parameters. The system we’ll be looking at is a modest – moderate home lighting system of 15 halogen luminaires. They will be a combination of 10 path lites and 5 spotlights. Let’s say the total wattages of all the lamps in the luminaires is 300 watts. Watts are a unit of electrical energy. We pay for our electricity in Kilowatt hours (1000 Kwh). Our system comes on when it gets dark and it knows this because we have a photoreceptor cell hooked to the transformer that measures when it gets dark. The transformer is what is hooked into our home electrical lines and steps down the 120 volt current to low voltage (12volts) to run our lights. We set the clock on the transformer to turn off at midnight, because, unless we’re using it for security lighting, we’ll be in bed by then (or at least I will) and cannot further enjoy the lighting.

The lights are scheduled to come on every day of the year. They’ll be on longer in winter and shorter in summer so, on average about 5 hours a day. . . .HEY!!! GET BACK HERE! SIT DOWN! Yea, I know this is boring, but stick it out. Trust me, you’ll be a better person for it. . . . .

5 hours/day x 365 days/year = 1,825 hours of lighting

1 hour on = 300 watts of power used

1825 hours of lighting x 300 watts = 547.5 Kwh (Kilowatt hours)

Total electrical cost to run the system for a year = 547.5 X .11/Kwh *= $60.23/year or $5.02/month

*(I got the $/Kwh by taking my monthly electric bill statement and dividing it by the Kwh used for the month)

Total cost to maintain the system (replace bulbs every 2 years)based on a 10 year cycle:
by owner ~ $45/yr (Electric + bulbs =~$8.77/month)
by contractor ~$90/yr (Electric + bulbs + labor =~$13.77/month)

WAIT A MINUTE!! Sit tight we’re almost done!

Now, what if I used low voltage LED lights? How much less would that be? The lower wattages of LED bulbs will equate to about 120 watts instead of 300. The other variable will be the cost of maintenance because we shouldn’t have to replace our bulbs for perhaps 10 years. All the rest of the equation is the same. I know you’re getting antsy and you have stuck with me this long (but I had to threaten you to do so), so I’ll skip the detailed calculations and reveal that the monthly cost of electricity ($2/month) + bulbs (based on a 10 year life @ $45/bulb + Labor= 7.25 month) = $7.63/month Now let’s say that the cost of installing that LED system was $1000 more. With the energy savings of LED we can pay for that in 13.5 years . . . .just about the time we’ll have to replace the LED bulbs. The savings and hence the difference between them cost-wise is in the added frequency of bulbs and labor to change out and the increased electrical cost. You had to sit through that and the conclusion to that isn’t all that dramatic . . . .BUT (and notice that’s a big “but” I’ve spelled there) that is contingent on electrical rates staying the same and the chances of that happening are worse than the chances of this article winning a Pulitzer.

For my money, I’d go with LED. In fact, in my own system I have both a run of LED lights and a run of halogen. In 8 years time I’ll tell you how they’ve fared.

F & P