power consumption of led flood lights

The illuminated sign energy consumption and cost calculation is simple yet confusing when you have to consider such things as power factor correction, ballast factor and efficiency of typical power conversion devices used in today’s illuminated signs.

In light of this, how do you determine power consumption of led flood lights ?

Let’s understand the basics before we look at the mathematics involved!

Lighting Formulas

Incandescent Lighting: Watts* X hours per day = watt-hours per day; X days per year = watt-hours per year; ÷ 1,000 = kWh per year; X energy cost per kWh = total annual energy cost.

Fluorescent and HID Lighting: Watts* X hours per day = watt-hours per day; X days per year = watt-hours per year; ÷ 1,000 = kWh per year. Total kWh per year X energy cost per kWh = total annual energy cost.

* Total wattage for all energy consuming devices in a sign

Here are some examples on how to calculate per-year energy-use costs for a medium size sign:

Ever wonder how much that light bulb is costing you? Is it really worth switching to compact fluorescent or LED flood lights ? All you need to find out is the bulb’s wattage and the cost of electricity in your building. Replacing your incandescent bulbs with energy-efficient options typically saves a few dollars in the first year, and more over a longer period of time.

1.Find the wattage rating of the bulb. The wattage is often printed directly on the bulb as a number followed by a W. If you don’t see it there, check the packaging the bulb was sold in. The watt is a unit of power, measuring the energy the bulb uses each second.

Ignore phrases like “100-watt equivalent,” which are used to compare brightness. You want the actual number of watts the bulb uses.

2.Divide this number by one thousand. This converts the number from watts to kilowatts. An easy way to divide by one thousand is to move the decimal point three places to the left.

Example 1: A typical incandescent bulb draws 60 watts of power, or 60 / 1000 = 0.06 kilowatts.

Example 2: A typical fluorescent bulb uses 15 watts, or 15 / 1000 = 0.015 kW. This bulb only uses ¼ as much power as the bulb in example 1, since 15 / 60 = ¼.


Estimate the number hours the bulb is on per month. To calculate your utility bill, you’ll need to know how much you use your bulb. Assuming you receive monthly utility bills, count up the number of hours the bulb is on in a typical month.

Example 1: Your 0.06 kW bulb is turned on for 6 hours a day, every day. In a 30-day month, that’s a total of (30 days/month * 6 hrs/day) = 180 hours per month.

Example 2: Your 0.015 kW fluorescent bulb is on for 3.5 hours a day, 2 days a week. In one month, it will be on for roughly (3.5 hours/day * 2 days/wk * 4 wks/month) = 28 hours per month.


Multiply the kilowatt use by the number of hours. Your energy company charges you for each “kilowatt-hour” (kWh), or each kilowatt of power in use for one hour. To find the kilowatt-hours your light bulb consumes per month, multiply the kilowatt use by the number of hours it’s on each month.

Example 1: The incandescent bulb uses 0.06 kW of power and is on for 180 hours a month. Its energy usage is (0.06 kW * 180 hours/month) = 10.8 kilowatt-hours per month.

Example 2: The fluorescent bulb uses 0.015 kW and is on for 28 hours a month. Its energy usage is (0.015 kW * 28 hours/month) = 0.42 kilowatt-hours per month.

Step 1: Capacity
Let’s use our 5/8” diameter hose which we will assume carries 16 gallons per minute

Let’s use a 60W (0.06kW) incandescent bulb
Step 2: TimeLet’s run the hose for 20 minutesLet’s operate the light bulb for 2,000 hours
Step 3: Consumption16 gal/ min x 20 min
320 gal consumed
0.06 kW x 2,000 hrs 
120 kWh consumed


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