ᐅ Sizing the Main Electrical Connection (for Photovoltaic Systems, Heat Pumps, and Electric Vehicle Charging Stations)
Created on: 2 Jan 2025 14:02
B
Bauen68
Dear forum,
We have received an offer from our utility provider for the electrical house connection.
After consulting with our house builder, we are planning for a 37 kW (kilowatt) house connection (assumption: 4-person household, air-to-water heat pump, charging station with max 22 kW, photovoltaic system with about 10 kWp).
The offer for the electrical connection specifies a NAYY 4x 35 mm² (4x 0.014 in²) cable.
The distance between the street and the house connection room is 7 meters (23 feet).
Since the power demand is over 30 kW, a construction cost contribution applies, which, according to my research, is reasonable since this deviates from the standard.
My questions:
1. Is the specified cable size (cross-section) appropriate as mentioned above, and should we consider or inquire about anything else with the utility provider?
2. Many sources mention how the circuit protection should be designed. The utility provider did not provide any information on this (only the cable size as above). Are there any precautions we should take or recommendations on the proper circuit protection for the needs described?
Thank you in advance for your help!
We have received an offer from our utility provider for the electrical house connection.
After consulting with our house builder, we are planning for a 37 kW (kilowatt) house connection (assumption: 4-person household, air-to-water heat pump, charging station with max 22 kW, photovoltaic system with about 10 kWp).
The offer for the electrical connection specifies a NAYY 4x 35 mm² (4x 0.014 in²) cable.
The distance between the street and the house connection room is 7 meters (23 feet).
Since the power demand is over 30 kW, a construction cost contribution applies, which, according to my research, is reasonable since this deviates from the standard.
My questions:
1. Is the specified cable size (cross-section) appropriate as mentioned above, and should we consider or inquire about anything else with the utility provider?
2. Many sources mention how the circuit protection should be designed. The utility provider did not provide any information on this (only the cable size as above). Are there any precautions we should take or recommendations on the proper circuit protection for the needs described?
Thank you in advance for your help!
M
MachsSelbst3 Jan 2025 00:27Does your energy supplier even approve a 22 kW wallbox?
A 35 mm² (0.05 inch²) cable is easily sufficient for 63 A, which equals 43 kW.
More than 63 A is usually difficult with many utility companies anyway. They often don’t see why a typical single-family home should be supplied with the capacity of an average 8-unit apartment building... and in the end, the cables under the sidewalk or street must also support this, otherwise the NH fuse will blow and the entire street block will lose power...
And whether 4-core or 5-core... the cost is almost the same because 5x35 mm² (0.05 inch²) cables are much more common and sold in larger quantities.
A 35 mm² (0.05 inch²) cable is easily sufficient for 63 A, which equals 43 kW.
More than 63 A is usually difficult with many utility companies anyway. They often don’t see why a typical single-family home should be supplied with the capacity of an average 8-unit apartment building... and in the end, the cables under the sidewalk or street must also support this, otherwise the NH fuse will blow and the entire street block will lose power...
And whether 4-core or 5-core... the cost is almost the same because 5x35 mm² (0.05 inch²) cables are much more common and sold in larger quantities.
M
MachsSelbst3 Jan 2025 13:02By the way, a house electrical connection is not designed with the expectation that all appliances will run at full power at the same time—and they don’t.
An electric cooktop from the 1990s can draw up to 11kW briefly if all burners are set to the highest setting. Once the water boils, the burner only cycles to maintain the temperature, and anyone can ask themselves how often they actually use three cooking zones at the highest level simultaneously. This also applies to the oven or coffee machine. The maximum power is not drawn continuously for hours.
The same goes for the electric kettle, which only uses its 2 kW for about a minute to heat the water.
Furthermore, an NH fuse has an overload characteristic—it does not trip immediately at 63A, but only after sustained current of about 1.25 to 1.6 times rated current over a period of up to an hour. For larger fuses with 630A, this period can be several hours.
You can think of it like a highway. It is designed for average traffic flow, not the peak at the start of a holiday.
And finally:
The current-carrying capacity for 35mm² (approximately 2 AWG) cable with three loaded conductors buried directly in the ground (installation method D) is 98A.
An electric cooktop from the 1990s can draw up to 11kW briefly if all burners are set to the highest setting. Once the water boils, the burner only cycles to maintain the temperature, and anyone can ask themselves how often they actually use three cooking zones at the highest level simultaneously. This also applies to the oven or coffee machine. The maximum power is not drawn continuously for hours.
The same goes for the electric kettle, which only uses its 2 kW for about a minute to heat the water.
Furthermore, an NH fuse has an overload characteristic—it does not trip immediately at 63A, but only after sustained current of about 1.25 to 1.6 times rated current over a period of up to an hour. For larger fuses with 630A, this period can be several hours.
You can think of it like a highway. It is designed for average traffic flow, not the peak at the start of a holiday.
And finally:
The current-carrying capacity for 35mm² (approximately 2 AWG) cable with three loaded conductors buried directly in the ground (installation method D) is 98A.
T
Teimo198816 Jan 2025 12:27As MachsSelbst mentioned, what you have is a standard connection for a single-family house, protected with a 63 A circuit breaker. This is completely sufficient for your needs.
Here, for a small additional cost (I think around 200€), 100 A connections are also available. It’s an option if the extra cost is low. I opted for it myself, but that was for a two-family house. To be honest, the 63 A connection would have been enough there as well...
Here, for a small additional cost (I think around 200€), 100 A connections are also available. It’s an option if the extra cost is low. I opted for it myself, but that was for a two-family house. To be honest, the 63 A connection would have been enough there as well...
M
MachsSelbst16 Jan 2025 14:24However, a 100A circuit can no longer be run with 5x35 mm² (5x35 mm² (1 AWG)) NYY-J cable buried underground; instead, 5x50 mm² (5x50 mm² (1/0 AWG)) cable must be used.
63A (63 amps) is more than sufficient, especially since the future will inevitably require devices in households, neighbors, streets, and even entire neighborhoods to be interconnected and intelligently controlled or coordinated.
The mindset of "I want to draw my full 44 kW whenever I want and for as long as I want" cannot support a successful energy transition.
63A (63 amps) is more than sufficient, especially since the future will inevitably require devices in households, neighbors, streets, and even entire neighborhoods to be interconnected and intelligently controlled or coordinated.
The mindset of "I want to draw my full 44 kW whenever I want and for as long as I want" cannot support a successful energy transition.
T
Teimo198816 Jan 2025 14:27I haven’t mentioned anything about the cross-section either. I’d rather avoid a discussion about the energy transition.
A
Allthewayup16 Jan 2025 21:39We paid about €700 on top to the local utility provider to upgrade the capacity from 50 to 63A. Would I do it again? Absolutely not. As others have already mentioned, 50A is sufficient for a single-family house, even with an 11kW wallbox and a heat pump. A 22kW wallbox is still possible, provided it’s not the middle of winter and the heat pump and other appliances are not running at full power simultaneously.
Additionally, with a 50A meter fuse (instead of the standard 35A), wiring in the distribution board sometimes needs to be done with 16mm² (0.021 in²) cables. My electrician charged a bit extra for that as well.
Additionally, with a 50A meter fuse (instead of the standard 35A), wiring in the distribution board sometimes needs to be done with 16mm² (0.021 in²) cables. My electrician charged a bit extra for that as well.
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