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

## 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 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

## 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)

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

458 Watts - 200 Watts = 258 Watts

-Or-

\$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

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;