[mamayer]

What is the best way to compare the overall savings of switching out an entire buildings existing 40w tube lighting and replacing it with t8 led lighting?

[mamayer]

I was thinking in the form of some kind of formula that calculates the overall price of each bulb over a 10 year span.

[Perito]

I think a T8 bulb is usually around 20 watts. If that is correct, then when compared to a 40 watt fluorescent, your cost will be

, so as an estimate, they will cost half as much as a 40-watt bulb for electricity.

Basically, just divide the wattage of the T8 LED bulb by the wattage of the comparable fluorescent bulb. You multiply the fraction times the total yearly cost with 40w bulbs, and you'll have your answer. Of course, this doesn't count the cost of the bulb, itself. It also doesn't factor in the life of the bulb. This is just electricity cost.

[tkrussell]

Perito gave you the watts saved and annual energy cost.

The standard T8 is 32 watts, but with a proper ballast the input watts for two is typically 58 watts, less than the sum of the two, so ballast info is important.

There are new High Performance T8 lamps, one as low as 25 watts, again ballast info is important.

My point is don't just add lamp wattage, if your trying to do a cost analysis, you will cheat yourself out o dollars for true watts saved.

Be sure to include any power supply for an LED unit.

What LED lamp are you looking at? I have not seen any worth their while, yet. New stuff comes out weekly. Ones I have seen are expensive $150-200 range each, and pure white to bluish light.

What exactly are you looking for?

Payback or Return on Investment?

Include annual maintenance costs savings?

Explain:
some kind of formula that calculates the overall price of each bulb over a 10 year span.

If you provide all the data I need I have a spread sheet I can run it through and produce all the numbers needed to give to a CEO and make a decision whether to proceed with a capitol project such as this.

What do you need?

[andrewc24301]

Do they emit the same amount of light? It sames that would factor in the final equation.

[tkrussell]

Retrofitting, or replacing any lighting system with something new energy saving measure, should always meet or exceed current lighting levels.

What needs to be calculated is the lumen depreciation of the new lamp or system. This calculates as part of the maintenance costs.

Mamayer is looking for a quick simple calculation, and to arrive at all the true projected costs, that does not exist. Once he/she gets back with more info, we can continue.