Landscape lighting systems consume electrical power.  And alas, electrical power costs money. Therefore, unless money is no object, it’s reasonable to ask how much it costs to power a landscape lighting system. Obviously, any homeowner thinking of having a system put in should perform this due diligence. Likewise, since we’re going to base our math on LED bulbs, a homeowner thinking of converting from halogen should, too.

Naturally, the most exact estimates need to take into account a slew of factors which are beyond the scope of this discussion. Nevertheless, we can reach a useful figure for landscape lighting power costs by making a few simple assumptions.

ELECTRICITY PRICES AND CONSUMPTION

First, there’s the price of electricity. In the Houston area, rates range from 9.5 cents to 10.4 cents per kilowatt-hour.  Those are what a customer is charged to draw 1 kilowatt for one hour. Incidentally, the national average is more like 12 cents.

Next, there’s the amount of power a landscape lighting system consumes. This is mostly determined by the number of bulbs in the system. In addition, transformers are not perfectly efficient, so a little more than X kilowatts have to go into one to get X kilowatts out. Since this loss is very small for modern electronic transformers ( up to 300 watts) we’ll set this aside.  There’s always some additional loss due to wiring, but it’s minimal so we’ll ignore it.

USAGE

Finally, we have to reckon how many hours, on the average, the system will be lit each 24-hour day. Dusk to dawn is a  reasonable mark.

Let’s calculate the basic power cost, then, for a system with 15 15-watt LED bulbs on a 300-watt transformer.  The bulbs draw a total of 15 x 15 or 225 watts. Over 12 hours, then, they’ll use 2.7-kilowatt hours. Over 30 days, 81 kilowatt-hours.  At 9.7 cents per kilowatt-hour, the bill would be about $7.85 per month.  We could round that up to $10 for transformer and wiring loss to be conservative. Naturally, transformers with add-on devices like timers and digital controllers use some power even when the lights are off.

CALCULATE LANDSCAPE LIGHTING COSTS ONLINE

There’s a handy online calculator you can use to estimate consumption and costs for any landscape lighting system you have in mind.  You can use also use it to “audit” a system you’ve already installed. Still in the halogen era? Thinking of converting to LED? If so,  it would be very instructive to use the calculator’s LED comparison feature. The projected savings in your landscape lighting power costs will probably please you greatly.