ᐅ How much can I actually save by building with KfW compared to standard construction?
Created on: 7 Dec 2012 00:42
G
Gluecklich
The title says it all:
What do I actually save by building a KfW house in comparison?
Under the same conditions: How much money do I save annually by building a KfW house?
Are there any calculations available for this?
What do I actually save by building a KfW house in comparison?
Under the same conditions: How much money do I save annually by building a KfW house?
Are there any calculations available for this?
Hello Gluecklich,
I had different options calculated.
But a KFW house is not just a KFW house.
There are various measures with different effects, all of which can lead to KFW certification. Each measure has different costs and varies in how much energy it saves.
You can either improve insulation, rely on alternative energy sources, or design the heating system differently.
There are also intermediate solutions combining several measures. Depending on the climate location, more or less of each measure may be necessary.
To give an extreme example:
Your house narrowly misses the KFW standard and is therefore classified as an energy-saving ordinance house.
Now, if you eliminate the bay window, you reduce the exterior surface area and heat loss, pay a bit less for the house, and suddenly have a KFW 70 house. The actual energy saving might not be significant, but the change pays off financially right away.
A "precisely KFW 70 house" is very rare in practice. If you achieve the status, it will in 99.99% of cases perform better than the minimum requirements. That means the investment is usually higher, but you don't have a three-quarter heating system.
If you approach the concept theoretically, a KFW 70 house must be 30% better than an energy-saving ordinance house. The energy-saving ordinance house is based on an oil heating system.
If you find energy consumption data for such a house, take 30% off that amount, and multiply it by the current oil price, you get a theoretical saving. This number will change tomorrow because oil prices fluctuate. However, this calculation has nothing to do with practical reality.
(@€uro I am aware other energy sources are involved, so my calculation isn’t 100% precise.)
To give some concrete numbers:
Our house with a gas condensing boiler and solar panels falls between the energy-saving ordinance and KFW 70 standards. With an air source heat pump or ground collector, we perform better than KFW 70 (additional cost minus gas connection around 8,000€). With deep drilling, we almost reach KFW 55, but would need additional insulation.
Comparing the three heating options, the ground collector is likely the most cost-effective for us, though all types are relatively close in cost. This also depends on expected energy price increases. Ignoring price rises, the gas condensing boiler would be the best option.
According to calculations by our independent construction and energy consultant, the ground collector pays off after 17 years. This does not factor in the improved loan interest on the remaining 42,000€ (50,000€ KFW loan minus 8,000€ extra heating costs), which would reduce the payback time further.
The average monthly saving required to break even on the collector compared to the gas condensing boiler, including interest, is about 8,000€/17 years/12 months = 40€ per month.
So there is one figure from us, but it won’t help you because you want to build a prefabricated house with a completely different shape in a very different part of Germany.
I had different options calculated.
But a KFW house is not just a KFW house.
There are various measures with different effects, all of which can lead to KFW certification. Each measure has different costs and varies in how much energy it saves.
You can either improve insulation, rely on alternative energy sources, or design the heating system differently.
There are also intermediate solutions combining several measures. Depending on the climate location, more or less of each measure may be necessary.
To give an extreme example:
Your house narrowly misses the KFW standard and is therefore classified as an energy-saving ordinance house.
Now, if you eliminate the bay window, you reduce the exterior surface area and heat loss, pay a bit less for the house, and suddenly have a KFW 70 house. The actual energy saving might not be significant, but the change pays off financially right away.
A "precisely KFW 70 house" is very rare in practice. If you achieve the status, it will in 99.99% of cases perform better than the minimum requirements. That means the investment is usually higher, but you don't have a three-quarter heating system.
If you approach the concept theoretically, a KFW 70 house must be 30% better than an energy-saving ordinance house. The energy-saving ordinance house is based on an oil heating system.
If you find energy consumption data for such a house, take 30% off that amount, and multiply it by the current oil price, you get a theoretical saving. This number will change tomorrow because oil prices fluctuate. However, this calculation has nothing to do with practical reality.
(@€uro I am aware other energy sources are involved, so my calculation isn’t 100% precise.)
To give some concrete numbers:
Our house with a gas condensing boiler and solar panels falls between the energy-saving ordinance and KFW 70 standards. With an air source heat pump or ground collector, we perform better than KFW 70 (additional cost minus gas connection around 8,000€). With deep drilling, we almost reach KFW 55, but would need additional insulation.
Comparing the three heating options, the ground collector is likely the most cost-effective for us, though all types are relatively close in cost. This also depends on expected energy price increases. Ignoring price rises, the gas condensing boiler would be the best option.
According to calculations by our independent construction and energy consultant, the ground collector pays off after 17 years. This does not factor in the improved loan interest on the remaining 42,000€ (50,000€ KFW loan minus 8,000€ extra heating costs), which would reduce the payback time further.
The average monthly saving required to break even on the collector compared to the gas condensing boiler, including interest, is about 8,000€/17 years/12 months = 40€ per month.
So there is one figure from us, but it won’t help you because you want to build a prefabricated house with a completely different shape in a very different part of Germany.
Bauexperte schrieb:
...Based on the graphic below, you should get an initial overview.... This will be of limited help, as primary energy is mainly of political interest. The operator is primarily concerned with the final energy they have to pay for. The importance of this will become clear with the revision of the energy saving ordinance (primary energy factor for electricity). Best regards
Musketier schrieb:
....So you have a figure from us, .. What demand and consumption were determined for the individual options?Best regards
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