Hello everyone,
I already have several energy performance certificates showing that for KfW55, a final energy demand of about 17 kWh/m²a (5.2 kBtu/ft² per year) has been calculated. This corresponds to an annual final energy demand of 2550 kWh/a (8700 kBtu/year) for a heated area of 150 m² (1615 ft²). The insulation, air-to-water heat pump, etc., also match my planned new build in timber frame construction. Here are my questions, as I feel a bit stuck:
1.) Has anyone had experience with similar figures and can confirm that these calculated values are realistic in practice?
2.) Can these numbers really be accurate, that only 2550 kWh/a (8700 kBtu/year) are needed? With electricity costs of €0.22, that would be only €560, and heat pumps produce more kilowatts of heat per kilowatt of electricity consumed.
3.) How exactly are the seasonal performance factors (seasonal COPs) calculated based on this final energy demand?
I have different seasonal performance factors for various heat pumps. I want to calculate the annual electricity demand in order to estimate running costs and assess from when a ground-source heat pump becomes worthwhile.
Split heat pump: 3.34
Monobloc heat pump: 3.67
Ground-source heat pump with horizontal loop: 4.67
Thank you very much
I already have several energy performance certificates showing that for KfW55, a final energy demand of about 17 kWh/m²a (5.2 kBtu/ft² per year) has been calculated. This corresponds to an annual final energy demand of 2550 kWh/a (8700 kBtu/year) for a heated area of 150 m² (1615 ft²). The insulation, air-to-water heat pump, etc., also match my planned new build in timber frame construction. Here are my questions, as I feel a bit stuck:
1.) Has anyone had experience with similar figures and can confirm that these calculated values are realistic in practice?
2.) Can these numbers really be accurate, that only 2550 kWh/a (8700 kBtu/year) are needed? With electricity costs of €0.22, that would be only €560, and heat pumps produce more kilowatts of heat per kilowatt of electricity consumed.
3.) How exactly are the seasonal performance factors (seasonal COPs) calculated based on this final energy demand?
I have different seasonal performance factors for various heat pumps. I want to calculate the annual electricity demand in order to estimate running costs and assess from when a ground-source heat pump becomes worthwhile.
Split heat pump: 3.34
Monobloc heat pump: 3.67
Ground-source heat pump with horizontal loop: 4.67
Thank you very much
World-e schrieb:
Usable floor area: 154.4 m² (1662 sq ft)
Heating energy demand: 45 kWh/m² per year
Primary energy demand: 37.2 kWh/m² per year
Final energy demand: 14.3 kWh/m² per year
System efficiency factor eP: 0.766
Annual renewable electricity production / photovoltaic system: 3000 kWh per year
Coverage ratio of photovoltaic system: 38.3%
From a heating engineer, I have data on different heat pumps and their annual performance factors (APF):
Split heat pump: 3.34
Monobloc heat pump: 3.67
Ground-source heat pump with horizontal collector: 4.67
2.) How can I use the existing data to compare the different heat pump types? Since the types vary in price and annual performance factor, I would like to know from when the more expensive variants become cost-effective. It would be great if someone could explain this to me or provide an example calculation. Regarding 2) I would simply ignore the solar production for heating, as it does not significantly contribute during winter or at night when heating demand is high.
So, 45 kWh/m² per year × 155 m² (1670 sq ft) = approximately 6975 kWh estimated heating demand per year.
Now divide this by the performance factors to find the electricity consumption, for example: 6975 / 3.34 = 2088 kWh or 6975 / 4.67 = 1493 kWh (a difference of about 600 kWh, roughly 130 USD per year).
This is only a very approximate calculation since it is based on estimated figures from the energy-saving regulations, your actual heating and usage patterns are not included, domestic hot water is not considered (which can significantly affect energy use, especially for air-to-water heat pumps on cold days when demand is high), and so on.
Too late for an edit:
I just took a look at my Energy Saving Ordinance calculations:
Planned KfW-70 house with 160 sqm (1722 sq ft) of living space
(The usable area stated in the certificate is 289 sqm (3111 sq ft), including the basement (insulated), which I am partially finishing myself).
Heating demand 44.27 kWh/m²a
Primary energy demand 42.16 kWh/m²a
Final energy demand 16.22 kWh/m²a
System efficiency factor eP: 0.743
The calculated heating energy demand was approximately 12,000 kWh.
My ground-source heat pump used 2,000 kWh of electricity in one year for heating and domestic hot water. You can already see that reality often looks different. For example, the Energy Saving Ordinance also specifies maximum (assumed) values for some window areas, but I know that my windows perform significantly better than those values. Thermal bridges are also only estimated on a generalized basis.
I just took a look at my Energy Saving Ordinance calculations:
Planned KfW-70 house with 160 sqm (1722 sq ft) of living space
(The usable area stated in the certificate is 289 sqm (3111 sq ft), including the basement (insulated), which I am partially finishing myself).
Heating demand 44.27 kWh/m²a
Primary energy demand 42.16 kWh/m²a
Final energy demand 16.22 kWh/m²a
System efficiency factor eP: 0.743
The calculated heating energy demand was approximately 12,000 kWh.
My ground-source heat pump used 2,000 kWh of electricity in one year for heating and domestic hot water. You can already see that reality often looks different. For example, the Energy Saving Ordinance also specifies maximum (assumed) values for some window areas, but I know that my windows perform significantly better than those values. Thermal bridges are also only estimated on a generalized basis.
nordanney schrieb:
If you start calculating, please also consider that a coverage rate of 38.3% from the photovoltaic system for heating is more than unrealistic, unless you have a storage system. If you are operating the photovoltaic system as a business, you MUST also include your own electricity consumption with VAT and record it in your profit and loss statement (and then pay tax on it in your income tax return). So, the electricity is not free... I can’t comment on the coverage rate, only that you shouldn’t expect much photovoltaic yield from December to January. The VAT obligation with photovoltaic systems is done to reclaim VAT on purchase costs and can be ended after 5 years. The electricity you use yourself is always free, roughly 10 cents/kWh. After the first 20 years, you only need to account for about 1 cent/kWh.
Otherwise, I am also considering whether a heat pump or direct electric heating will replace my current old oil heating system in a few years.
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