As already written -> The discussion with RotorMotor leads to no conclusion
No conclusion or just not to your conclusion? I am happy to remain available for concrete change proposals (including justification). I scrolled through again, so far I could only find this:
... because it does not include photovoltaics and household electricity and therefore the comparison cannot work. End of discussion!
Actually, photovoltaics were included, household electricity in the relevant period as well, but I will gladly highlight it for you again in red: 150m² with 40kWh/m²a -> 6000kWh/a heating energy demand 10kWp photovoltaics + 5kWh storage -> ~15kWh/day in Nov, Dec, Jan, Feb. With 10kWh for household electricity including hot water, 5kWh/day remain for heating The costs of photovoltaics are not listed in this example because the system already finances itself through feed-in tariffs and savings on household electricity. I omit hot water costs as both systems can provide it with SPF4 and thus it makes no difference; the electricity for hot water is included in household electricity in the calculation. Purchase electricity price 35ct/kWh Feed-in tariff price: 8.2ct/kWh Interest rate 3.5% (current interest for 10-year term) Electricity price increase 6% (average of the last 20 years)
Vestaxx + Photovoltaics: Extra cost over normal windows: €10,000 Purchase and installation of BWWP: €5,000 Interest on purchase over 18 years: €5,239 Maintenance BWWP: €200/year 4 [months] * 30 [days] * 5 [kWh/day] = 600 [kWh] from photovoltaic electricity Remaining 5400kWh as purchased electricity Totals (on average, due to rising electricity prices) 5400*(35+35*1.06^18)/2+600*8.2 = €3,691/year After 18 years, that makes: €90,286
Heat pump + Photovoltaics: Hydraulics: €80/m²*150m = €12,000 Purchase air-water heat pump monoblock and installation: €20,000 Interest on purchase over 18 years: €11,176 Maintenance air-water heat pump: €250/year Electricity demand: 6000/4 = 1500kWh Remaining 900 as purchased electricity Totals (on average, due to rising electricity prices) 900*(35+35*1.06^18)/2+600*8.2 = €656/year After 18 years, that makes: €59,488
Vestaxx without photovoltaics: Extra cost over normal windows: €10,000 Purchase and installation of BWWP: €5,000 Interest on purchase over 18 years: €5,239 Maintenance BWWP: €200/year Totals (on average, due to rising electricity prices) 6000*(35+35*1.06^18)/2+600*8.2 = €3,691/year After 18 years, that makes: €94,558
Heat pump without photovoltaics: Hydraulics: €80/m²*150m = €12,000 Purchase air-water heat pump monoblock and installation: €20,000 Interest on purchase over 18 years: €11,176 Maintenance air-water heat pump: €250/year Electricity demand: 6000/4 = 1500kWh Totals (on average, due to rising electricity prices) 1500*(35+35*1.06^18)/2 = €1,011/year After 18 years, that makes: €65,878 This results in additional costs for Vestaxx of €30,798 in this example compared to the heat pump. So for 18 years, every month
paying €142 more per month without having the underfloor heating remaining at the end of the term! All the money is gone to the energy supplier and largely converted into CO2.