Damaged Cargo For Sale

I received complimentary a 20-watt bulb, with the guarantee of 10,000 hours of operation. On the box it says: "Eat Smart". There is also written: "Initiative of Enel Distribuzione, funded through government incentives (DM 20 July 2004 and subsequent amendments). So
: the bulb that I apparently received a tribute from Enel, I actually bought it (the State has done, with my own money, giving them to Enel).
The packaging is also written that the bulb produces the same intensity of light from a normal 100 watt bulb. Doing a simple account
, 20 watts per 10,000 hours of operation are 200,000 Wh (watt-hours), corresponding to 200 kWh (kilowatt hours) of energy that the bulb would consume in its lifetime.
10,000 hours of life are estimated, on the packaging of the bulb, three hours a day for about 10 years.
At home I have 20 60-watt bulbs, however, are the same ones that took me 12 years ago. Thus, the life of the bulbs seem to be more than 10 years. I now
the hypothesis that during a week in winter they may remain switched on during the 4 lamps (thus corresponding to a total of 240 watts) for 5 hours a day in 5 working days (ie 25 hours in 5 days) and 10 hours a day on weekends, ie for two days (20 hours, figuring to spend the weekend at home). It follows, then, that four bulbs (Which are 240 Watt) remain on for 45 hours per week, which means 1170 hours in six months (26 weeks), during the winter months. I suggest that in the six summer months, they remain on for half the time: 585 hours. In one year, therefore, consume 240 watts for 1755 hours: 421,200 are Wh (watt-hours), which approximates to 420 kWh (kilowatt hours). Rubbing
this result on my 20 bulbs, I get that in a year each would consume 21,000 watt hours (kWh or 21, you get by 420,000 divided by 20) and being 60-watt bulbs, each of them would remain on for 350 hours. Would reach 10,000 hours of power in about 10 years, even as estimated by Enel.
If my 20-watt light bulbs were all rather than 60 Watt, consume one third of what they actually use. So, if every 60-watt bulb consumes 21 kWh per year, ie 210 kWh in 10 years, using 20W bulbs they would consume in ten years, I would save 70 kWh and 140 kWh of electricity.
to buy 20 60-watt bulb, currently spend about 40 euro, up from 160 € to spend on those with low consumption. If the latter, however, they cost 4 times more than normal, I suppose that to produce them is necessary to consume 4 times the energy that is consumed to produce light bulbs.
Expressing the result to the inequality:
4E + 70 kWh kWh kWh ≤ 210 kWh + E
becomes:
3E kWh ≤ 140 kWh which
:
E ≤ 47 kWh to produce
means that if a regular bulb will spend less than 47 kWh, it is convenient to replace the bulbs with energy-efficient ones (whose production would require 188 kWh), otherwise it should .
How much energy is consumed to produce a normal light bulb or an energy saving light bulbs? It would be interesting to find out ...