Water heater and economy of energy
I did not talk about energy savings about the water heater.
For the heating of the water with an electric water-heater, a household of four persons spend about 250€ each year.
An electric balloon of 300 litres costs 450€.
A thermodynamic water heat independant of 300 litres cost between 2500 and 3000€, let's take the most favorable case, this makes 2050€ more to save 50% on the hot water bill, that is to say 125€, because there is always a heating resistance to bring the water to 65İC because of the legionellosis :
2050 divided by 125 makes 16,4 years that is to say about 17 years to earn back its cost (with the current cost of energy).
Obiously, it is not placed in the bathroom, it is too much noisy
It exists also ballons, still with the additional resistance, anti-legionellosis, connected to the compressor of the heating system, the compressor is more expensive and it must be in permanence running, it is not very advantageous. The ballon costs about 2000€ and the compressor 500€ more, and it seems that it has some break down risks.
There is the solar water heater : 6000 to 7000€, there is also an additional resistance, not for the legionellosis but for the no-sun periods, the yield is estimated, depending on the areas, to 70% for the case that we are interested in (Pays de Loire). Let's take the favorable case, this makes 5550€ more to save 175€:
5550 divided by 175 makes 31,7 years, that is to say about 32 years to earn back the investment (still with the current energy currency), if you did'nt have to change it before!!
Of course, if the state pay you half of it, this is brought back to 16 years.
You can amortize it faster by taking many showers, mainly in summer days, because it gives hot water directly, but water cost increaser as faster as oil or almost !!!
It is an intimate conviction question : be ecological, or be thrifty.