I’ve recently take a look at the 15 years old halogen downlight lamps built-in the ceilings of my house. I counted up to 29 of them; they are 250V 50W halogen dichroic lamps. This lamps are installed typically in corridors, bathrooms, living room, reading/studying lamps,…

The point is that you can find equivalent diode lamps that provide similar luminous flux (between 350 – 500 lumen) with wattages ranging 3,5-5W and color temperatures between 3000-5000K at very competitive cost (less that 2€ in the supermarket I have in my neighborhood).

So just doing an easy calculation this is what we get:

{A}: [savings ratio] = [halogen wattage] / [diode wattage] = 50W/5W =10 (ten times!!)

The typical percentage of taxes in the bill is more than 50%, so approximately:

{B}: [bill€] = 2 x [consumption]

The typical percentage of illumination in the electricity bill is 20% in domestic (and around 40% in the public sector in streets, roads, highways, official buildings …)

Now we have got all the information for calculating the savings, therefore according to {A} and {B}:

[% Savings] = [1 - 1/[lightning savings ratio]] x [percentage of illumination in bill] x 2

[% Savings] = (1 - 1/10) x 0,2 x 2 = 1,1 x 0,2 x 2 = 4,4%

A typical domestic bill is 50€/month, therefore you save 50€ x 4,4% = **2,2€ which is the cost of renovation for one lamp**.

**Conclusions:**

The payback period in months is more or less the number of 50W halogen dichroic lamps you migth remove in your place, 60€ investment for the 30 lamps I’ve got, **2 years and a half** payback period in my particular use case.

If you are one of those guys that keeps all the lights switched on, students/elderly/domestic service people in your home, savings will be higher. In addition the tendency is that energy cost rates will increase over time.

If you already have low comsumption lamps installed (tipically wattage ranging 10-15w) it’s not worth changing them, you’d better renew as soon as they stop working. Anyway consider renewing those lamps that are switched on the more number of hours per day to lower the electricity bill.

I’ve changed all my halogen lamps in 2 hours, how many of them do you have installed in your house?

In comming blogs I’ll focus on the fidge and TV…

😉