ᐅ Calculation of Electricity Consumption Based on Heating Demand?
Created on: 8 Feb 2018 20:02
T
tecker2010
Hi,
maybe someone can help me out here.
If I know the heat demand of my house, how can I estimate the approximate annual electricity consumption from that?
My heat demand is roughly 10 kW (including hot water). What other values do I need to calculate the electricity usage? I plan to generate the heat with a monovalent air-to-water heat pump.
I keep coming across full load hours (usually given as a standard 2,000 hours) and the annual performance factor (seasonal coefficient of performance) of a heat pump. Is that all I need?
10 kW * 2,000 h (hours) = 20,000 kWh (heat energy).
20,000 kWh / 2.8 (annual performance factor) = 7,143 kWh of electricity used. Is that correct? I know a detailed calculation is much more complex (transmission losses, etc.). A rough estimation would be enough, but I think I might be missing something and also find the 2,000 full load hours too approximate.
Looking forward to your feedback.
maybe someone can help me out here.
If I know the heat demand of my house, how can I estimate the approximate annual electricity consumption from that?
My heat demand is roughly 10 kW (including hot water). What other values do I need to calculate the electricity usage? I plan to generate the heat with a monovalent air-to-water heat pump.
I keep coming across full load hours (usually given as a standard 2,000 hours) and the annual performance factor (seasonal coefficient of performance) of a heat pump. Is that all I need?
10 kW * 2,000 h (hours) = 20,000 kWh (heat energy).
20,000 kWh / 2.8 (annual performance factor) = 7,143 kWh of electricity used. Is that correct? I know a detailed calculation is much more complex (transmission losses, etc.). A rough estimation would be enough, but I think I might be missing something and also find the 2,000 full load hours too approximate.
Looking forward to your feedback.
@tecker2010 Your heat demand is definitely not 10 kW. Your car doesn’t consume 60 horsepower over 100 km either!
Perhaps you mean the heating load of your building with 10 kW. Whether this is realistic for a new build depends on the size and energy standard of your building. The heating load of a new building is usually determined as part of the building permit / planning permission process and the energy demand calculation according to the energy saving regulations.
A heating load of 10 kW means that your building, at an outdoor temperature between -10°C and -16°C (14°F to 3°F) depending on the region, can maintain an indoor temperature of 20°C (68°F) with 10 kW of heating power (including allowances for warming up).
A realistic value for new builds is around 35-50 W/m² (3.3-4.6 W/ft²).
From the heating load, as already mentioned, you can roughly estimate the required heat energy and from there, with known system technology, approximately the required electricity amount, but with significant uncertainty!
A more precise statement can be found in your heat demand calculation.
Perhaps you mean the heating load of your building with 10 kW. Whether this is realistic for a new build depends on the size and energy standard of your building. The heating load of a new building is usually determined as part of the building permit / planning permission process and the energy demand calculation according to the energy saving regulations.
A heating load of 10 kW means that your building, at an outdoor temperature between -10°C and -16°C (14°F to 3°F) depending on the region, can maintain an indoor temperature of 20°C (68°F) with 10 kW of heating power (including allowances for warming up).
A realistic value for new builds is around 35-50 W/m² (3.3-4.6 W/ft²).
From the heating load, as already mentioned, you can roughly estimate the required heat energy and from there, with known system technology, approximately the required electricity amount, but with significant uncertainty!
A more precise statement can be found in your heat demand calculation.
tecker20109 Feb 2018 12:00@dertill Sounds like a correction that heat demand is not expressed in kW? Am I understanding this correctly? However, it is stated like this everywhere =>
Living area [m² (square meters)] × specific heat demand [kW/m² (kW per square meter)] = building heat demand [kW]
But I’m happy to be corrected. After all, I’m not an engineer.
Living area [m² (square meters)] × specific heat demand [kW/m² (kW per square meter)] = building heat demand [kW]
But I’m happy to be corrected. After all, I’m not an engineer.
The heat demand is always given in kWh/m², not in kW/m².
The heating load for a building is generally specified in kW, without reference to the area.
These two should not be confused, as it only leads to misunderstandings. This might sound like a lecture, but I hope it is taken as a constructive note rather than as condescending.
kW = kilowatt = 1000 W is a unit of power.
kWh = kilowatt-hour = 1000 W over one hour is a unit of energy.
From the heat demand, you can quite quickly estimate the electricity consumption using the annual performance factor. Using the building’s heating load involves at least one additional step and is significantly less precise.
The heating load for a building is generally specified in kW, without reference to the area.
These two should not be confused, as it only leads to misunderstandings. This might sound like a lecture, but I hope it is taken as a constructive note rather than as condescending.
kW = kilowatt = 1000 W is a unit of power.
kWh = kilowatt-hour = 1000 W over one hour is a unit of energy.
From the heat demand, you can quite quickly estimate the electricity consumption using the annual performance factor. Using the building’s heating load involves at least one additional step and is significantly less precise.
tecker20109 Feb 2018 16:21Ok, thanks for the hint (I of course take that as constructive criticism). But quite a few websites seem to get it wrong.
When I search Google for the terms "heat demand" or "heat demand calculation" and look at the sites and example calculators, I repeatedly come across values given in kW (e.g., kesselheld).
In the energy performance certificate, however, the value is given in kWh/(m²·a).
On the internet, for example, I found the following statement:
"New building according to energy saving regulation: 0.04 kW/m²"
Multiplying this by our living area of 152 m² (1635 sqft) results in an approximate heating load (!) of 6.08 kW. My question here is whether I should multiply this by 1,800 hours to calculate the heat demand? That would then be 10,944 kWh. Or is it calculated differently?
When I search Google for the terms "heat demand" or "heat demand calculation" and look at the sites and example calculators, I repeatedly come across values given in kW (e.g., kesselheld).
In the energy performance certificate, however, the value is given in kWh/(m²·a).
On the internet, for example, I found the following statement:
"New building according to energy saving regulation: 0.04 kW/m²"
Multiplying this by our living area of 152 m² (1635 sqft) results in an approximate heating load (!) of 6.08 kW. My question here is whether I should multiply this by 1,800 hours to calculate the heat demand? That would then be 10,944 kWh. Or is it calculated differently?
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