How To Calculate Watts: 400 Metal Halide vs. T-5 High Bay Fluorescent

Posted by Jimmy Hovey on Tue, Aug 23, 2011 @ 16:08 PM

Which Fixture is More Efficient? 400 Watt Metal Halide or T-5 High Bay Fluorescent?

Read On To Learn More About How To Calculate Watts:

Difference in Wattage 400 Watt MH to T-5 High Bay


Calculating the cost benefits between a 400 Watt MH compared to a T-5 High Bay Fluorescent is a relatively simple calculation.  Calculating energy efficiency is actually simple subtraction problem. 

Looking at the 2 different fixtures above, we have to find the rated wattage of each fixture.   

A 400 Watt Metal Halide is rated at 458 Watts

A 4 lamp T-5 High Bay (Depending On Manufacturer) is right around 200 Watts

Now that we have that, we can do the math.

458 Watts - 200 Watts = 258 Watts Difference or 56% Less Watts 

With this information we can now determine how much each of the fixtures will cost us annually.   

How-to-calculate-watts-for-T-5-FluorescentHow To Calculate Kilowatt Hour (kwh)

A watt is only part of the calculation when figuring out how much your fixture is costing you.  But in order to show you how a watt fits in, we have to do a little more complicated math. 

By utilizing the wattages between the 2 fixtures, we can determine the cost difference between the 400 Watt MH and the T-5.  This will help you to understand how to determine the kwh. 

Here is the equation we need to use in order to do the math:

Fixture Quantity x Fixture Wattage = Total Watts

Total Watts / 1000 = Kilowatts

Kilowatts x (Hours of Usage) = Kilowatt/Hr

Kilowatt/Hr x (Cost of Energy) = Annual Cost

It Costs How Much?

Let's assume you have the following:

We are going use just 1 fixture for this example (Fixture Quantity)

458 Watt Fixture (Fixture Wattage for Each) - or -

                                 200 Watt Fixture (Fixture Wattage for Each)

2000 Hours (Hours of Usage)

$.10 Per Kilowatt/Hr (Average Energy Rate Charged)

How much does the 400 Watt MH cost  annually?

1(Fixtures) x 458 (Watts Each) = 458 Watts

458 Watts / 1000 = .458 kw

.458 kw x 2000 hrs per year = 916 kwh (Kilowatt) Annually

916 kwh x .10 = $91.60 to operate 1 400 Watt Metal Halide for 1 Year

How much does it cost annually to operate 1 - T-5 High Bay?

1 (Fixtures) x 200 (Watts Each) = 200 Watts

200 Watts / 1,000 = .20 Kw (Kilowatt)

.20 Kw x 2000 hrs per year = 400 kwh (Kilowatt Hour)

400 kwh x .10 = $40 to operate 1 T-5 High Bay Fluorescent


"Watt's" the difference? $51.60 Annual Savings

458 Watts - 200 Watts = 258 Watts


$91.60 - $ 40 = $51.60 In Annual Savings or 56% Savings

Multiply By The Number of Fixtures

If you have 100-400 Watt Metal Halides, then you would save $5160 per year if you ugraded to the T-5.

Have 500 of them?

Then your annual savings would be $25,800.

Can You See The Correlation?

If you just know the wattage of your existing fixture and the wattage of the new fixture, you can determine your annual energy savings:

458 Watts - 200 Watts = 258 Watts Difference or 56% Less Watts 

$91.60 - $ 40 = $51.60 In Annual Savings or 56% Savings

Want To Learn More About Energy Efficiency?

Energy efficiency calcualtions and terminology can sometimes be confusing.  We created a Free E-book to help you determine the best investments for your eneryg efficiency dollars.  To learn more, see the button below;

Need Help?

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Typcially we need to see the inside of your facility first hand to determine what type of lighting you have now and to measure the lighting levels. 

Hovey Electric can perform a complete audit of your facility to determine what is right for you, for FREE.  Let's take a look at your facility, it's FREE and no obligation required.

Topics: energy efficient lighting