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How much energy does a light pear use, and how go lighting affect your electrical energy bill? exactly how much will certainly a light retrofit conserve you? just how do you start to calculation the value of a potential lighting rebate?

There’s one common thread the runs v each of these questions: the difference in between watts (W), kilowatts (kW), and also kilowatt-hours (kWh). Calculating watt to kWh could help you understand the answers come the concerns above.

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The energy industry is almost as negative as the lighting sector at utilizing abbreviations and jargon, therefore we’ll shot to break each of this down v some valuable examples.

In this article, i’m going to usage the analogy the equating electrical energy to water. This is a typical analogy that us can’t case as our own, but hopefully our certain examples will assist explain just how much power lighting really uses.

If you already know the difference between kW and kWh, click below to run ahead come the calculator.

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What is a watt (W)?

You’ve more than likely made a lot of lighting decisions based on wattage. Girlfriend unscrew a burned out irradiate bulb and also look in ~ the top and see “60W.” all you have is a light bulb labeled “25W,” so friend screw that in, and to your dismay, it’s means too dim. You walk to the store and also pick out a “60W” bulb. Her lights are bright again. Situation averted.

So what is a watt, anyway? Technically speaking, it"s a unit of electrical power same to 1 joule per second. Irradiate bulbs room rated in watt to indicate exactly how much energy they consume.

Does the wattage the a light bulb have anything to carry out with brightness? Well, kind of.

For so long, plenty of of united state have connected watts v the amount of light a bulb gives off. In general, that works well with timeless incandescent irradiate bulbs. A 60W glow bulb frequently gives off approximately 650-800 lumens. A 25W glow bulb commonly produces about 150 lumens — much less light.

With the arrival of much more efficient lighting, though, that not unusual to check out a “60W equivalent” bulb the uses much less energy and also gives off around the exact same amount of light. This is a breakdown:

IncandescentHalogenCFLLED
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Wattage60W42W13-16W5-9W
Lumens every watt (LPW)1318.56075-100+

(The photos over are representative that the technology, not particular product specifications.)

So, together you space comparing light bulbs, remember the wattage is a measure up of just how much power the light bulb will use as that produces light, and the lumens will give you a measure up of exactly how much irradiate it will certainly produce.

Ready to shop light bulbs? Click here and use the filter on the left to sort by lumens.

What is a kilowatt (kW)?

Just choose watts, kilowatts is a measure of how much energy something will certainly consume. Walk from watts (W) to kilowatts (kW) is a pretty straightforward calculation: 1kW is equal to 1,000W. To transform W come kW, divide the complete wattage through 1,000.

Here’s an example: if girlfriend turned on ten 100W light bulbs, that would equal 1kW of power usage.

10 bulbs x 100W = 1,000W

1,000W / 1,000 = 1kW

It’s additionally worth noting that kW can be synonymous with “demand” if you’re talk to a energy company. Imagine the you revolve on those ten light bulbs and a 3,000-watt apparel dryer at the very same time. The utility agency needs to be able to supply enough electrical energy to fulfill that 4kW of demand at the moment you turn everything on.

Your energy usage, though, relies on exactly how long you keep everything on, i m sorry leads us to…

What is a kilowatt-hour (kWh)?


What’s the difference between kW and kWh? The kWh measure is a method to quantify how much energy is provided over a period of time. This have the right to be calculation by multiplying the kW of energy consumption by the total variety of hours the lighting has been operated.

Let’s go back to the instance of having ten 100W irradiate bulbs. How much power would you usage of the food of a month if you turn them on because that 10 hrs a day?

That’s wherein kWh comes into play. Here’s the breakdown:

10 bulbs X 100W = 1,000W or 1kW the lighting

10 hours of daily use X 30 days in the month = 300 hrs of use

1kW X 300 hours of usage = 300kWh of power consumption

So why is kWh so important if you deserve to compare light products based on wattage and light output? In the end, a far-ranging portion of your electrical energy bill is based on your energy intake in kilowatt-hours. If you want to calculate the dollar savings you’ll acquire from a retrofit to much more efficient lighting, kWh will come right into play.

kW vs kWh: A valuable example

Okay, sufficient theory.

How around a practical example to describe the difference in between kW and also kWh? (Here’s wherein the water analogy come in.)

Let’s imagine that we have two garden hoses, one through a 3/8-inch diameter and also one through a 5/8-inch diameter.


The 5/8-inch hose has actually a larger capacity 보다 the 3/8-inch hose, therefore it have the right to carry an ext water at any given moment. This is the idea of kW — the capacity to use electricity.

Now, let’s imagine the we desire to to fill up a two-gallon watering can. The amount of water that we use to to fill up the can is two gallons. This is the idea of kWh — the complete amount of power consumed end time.

How lengthy would it take to fill up the watering can? That relies on i beg your pardon hose we choose. The 5/8-inch hose — because of the bigger capacity — will fill increase the watering can an ext quickly 보다 the 3/8-inch hose.

In the exact same way, a 100W irradiate bulb will consume a full of 10kWh of power faster 보다 a 60W irradiate bulb.

Here is a parallel example:

WaterEnergy
Step 1: Capacity
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Let’s use our 5/8” diameter water tap which we will assume dead 16 gallons every minute
Let’s usage a 60W (0.06kW) incandescence bulb
Step 2: TimeLet’s operation the hose because that 20 minutesLet’s operate the light pear for 2,000 hours
Step 3: Consumption16 gal/ min x 20 min= 320 gal consumed0.06 kW x 2,000 hrs = 120 kWh consumed

Let’s lug in the effectiveness piece to the example and compare an glow light pear to an LED irradiate bulb:

EnergyEnergy
Step 1: Capacity60W (0.06kW) glow bulb5W (0.005kW)LED bulb
Step 2: TimeLet’s operate the light bulb for 2,000 hoursLet’s operate the light bulb for 2,000 hours.
Step 3: Consumption10.06 kW x 2,000 hrs = 120 kWh consumed0.005 kW X 2,000 hrs =10 kWh consumed

In this example, we obtained the same light output, and we activate the light bulbs for the exact same amount the time, however the total energy intake over the 2,000 hrs of operation was 110 kWh less for the LED bulb.

W vs kWh in bright rebates


Lighting rebate programs space one area wherein we tend to see the difference between a wattage reduction and also kWh consumption reduction top top a regular basis.

In general, there room two kinds of bright rebates we run across:

1. Demand-reduction light rebates

Some bright rebates are concentrated on the wattage palliation of a retrofit. If you change a 100W PAR38 bulb v a much more efficient 14W LED PAR38, the utility will salary a rebate based on the 76 watts of power reduced.

2. Usage-reduction bright rebates

Other lighting rebates are focused on the as whole reduction in energy intake for a retrofit. If you run your lighting for 4,320 hours per year (12 hours per day, 360 days per year), the 100W PAR38 would usage 432 kWh per year and also the 14W LED PAR38 would use just over 60 kWh per year.

In this case, the energy would salary a rebate based upon the 372 kWh that energy usage saved end the course of the year from the an ext efficient lighting.

Trying to make feeling of the myriad of lighting rebates available throughout the country?We"re here to help.

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Hopefully our explanation the the difference in between watts, kilowatts, and kilowatt-hours is helpful.

We want to do this as easy as possible, therefore we’ve put together a calculator that you have the right to use to easily — and also easily — get the number you need.

Watts come kWh calculator


Now that you’re a agree at learning the difference in between kW and also kWh, check out our posts on understanding the total cost of bright or how to calculate power savings and payback because that lighting projects.