Energy saving. What is more profitable?

Energy saving in numbers.

Written based on the topic in Q & A
The question is marked as resolved, but I do not like this calculation ... where are the habrosomer and habro-erudition?
So, a specific task is given:
Energy saving light bulb:
Price - 120 rubles
Power - 15 W
Lifetime claimed by the manufacturer - 8000 hours

Plain light:
Price - 10 rubles
Power - 60 W
The service life declared by the manufacturer is 1000 hours
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The cost of 1 kW / h - 1.96 rubles.

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I want to note, and for me it is important that for 120 rubles you get not only savings, but also a guarantee for it in 1 year, and there are no guarantees for incandescent lamps. Formally, of course, we can use ZOZPP, but the article is not about that.

The pros and cons of incandescent and fluorescent lamps will not be discussed here either, they have already been considered .

Get to the point. Actually, the calculations themselves are in the question not “what is more profitable?” (For what is more profitable - and this is understandable), and when, with such a difference in price, the savings will pay off and start saving? It is not difficult to calculate:

1. 60 - 15 = 45 W (so we save per hour)
2. 120 - 10 = 110 rubles. (this amount must be worked out to start saving)
3. (110 / 1,96) so many kWh need to work to pay off. We translate into watts and divide by the number of watts we save per hour, we get * 1000/45 = 1247.16 hours.

So we got a specific answer for the task.
As a result, with an average of 8-10 hours a day, we begin to receive PROFIT in 4-6 months. By the time the incandescent lamp is already working out its term of 1000 hours.
PS From myself I will add, I use saving lamps for more than two years. All 8 pieces are still working properly.