Vestaxx window heating - experiences?

  • Erstellt am 2021-11-13 20:56:37

chand1986

2022-10-09 21:34:10
  • #1


I appreciate your accuracy, but as a natural scientist, I am even more a friend of Occam's razor: to look for the simplest solution to a problem! (in a figurative sense)

says that for the price of a heat pump alone, you roughly get his system plus a photovoltaic system.
So he compares like that.

The correct way now would be to compare his system with photovoltaic against a heat pump with photovoltaic and to include the additional interest costs of the higher investment.
Added to that are the lifetimes of the systems and the replacement costs after time x.

These aren’t actually that many numbers.

I would also take them as running text, as long as it doesn’t end up in a wall of text.
 

RotorMotor

2022-10-09 22:15:37
  • #2


Here is the calculation from the previous example again with interest.
Of course, as mentioned before, the electricity price increase must also be taken into account!
Let's calculate the whole thing over 18 years because the managing director always wants the VDI 2067, and it states this as the "lifetime" for a heat pump:

150m² with 40kWh/m²a -> 6000kWh/a heating energy demand
10kWp photovoltaic + 5kWh storage -> ~15kWh/day in Nov, Dec, Jan, Feb. With 10kWh for household electricity including hot water, 5kWh/day remain for heating.
I leave out hot water each time because both systems can provide it with a COP of 4, thus making no difference; the electricity for hot water is included in household electricity.
Electricity purchase price 35ct/kWh
Feed-in tariff price: 8.2ct/kWh
Interest 3.5% (current interest for 10 years fixed)
Electricity price increase 6% (average of the last 20 years)

Vestaxx:
Surcharge on normal windows: 10,000€
Purchase and installation BWWP: 5,000€
Interest for the purchase over 18 years: 5,239€
4 [months] * 30 [days] * 5 [kWh/day] = 600 [kWh] from photovoltaic electricity
Remaining 5400kWh as purchase
Totals to (average, due to rising electricity prices) 5400*(35+35*1.06^18)/2 + 600*8.2 = 3,691€/year
after 18 years that results in: 86,686€

Heat pump:
Hydraulics: 80€/m²*150m = 12,000€
Purchase air-water heat pump monoblock and installation: 20,000€
Interest for the purchase over 18 years: 11,176€
Electricity demand: 6000/4=1500kWh
Remaining 900 to purchase
Totals to (average, due to rising electricity prices) 900*(35+35*1.06^18)/2 + 600*8.2 = 656€/year
after 18 years that results in: 54,988€

This results in additional costs for Vestaxx in this example of 31,697€ compared to the heat pump.
 

chand1986

2022-10-10 04:02:31
  • #3


Something like that.

I’m now playing devil’s advocate and say: maintenance/repair plus replacement are missing for the heat pump. assumes that in the above-mentioned period the heat pump will be worn out towards the end and needs to be renewed, but the heating windows are maintenance-free and last until you want new windows anyway.

If roughly 30k accumulate over 18 years, during which normal inflation also continues, does that work out?

(I assume that is what the legendary business administration texts are aimed at?)
 

filosof

2022-10-10 06:21:39
  • #4


Then please also include maintenance, repair, and replacement of the domestic hot water heat pump required for the window heating ;-)
 

chand1986

2022-10-10 07:17:04
  • #5

Correct!

Words words words words
 

kati1337

2022-10-10 08:31:26
  • #6
I also find the thesis "the other system breaks down, ours doesn't" pretty bold. ;)
 

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