ᐅ Gas Price Increase Effective January 1, 2022

Hello,

tomtom79 schrieb:

Can you equate the amount of heat produced by the heat pump directly with kWh, or how do you calculate that?

As a rough estimate, you can calculate it like this:
For a gas heating system, the kWh of the gas consumed corresponds to the amount of heat you deliver into the building.
A heat pump produces heat equal to the electricity consumed multiplied by the seasonal performance factor (SPF).
The seasonal performance factor represents the average efficiency over the whole year. The nice catalog values for COP = 5 or higher are unfortunately maximum values under ideal conditions and don’t reflect real-world performance.
It’s also important to note that the electricity used for backup heaters (either for domestic hot water heating or to support heating during very cold weather) is not included in the SPF. This means the actual efficiency can be considerably lower in practice.

Best regards,

Andreas

Hello,

Hangman schrieb:

Theoretically yes. In my previous gas bills, the cubic meter was always converted to calorific value in kWh. This is supposed to ensure comparability.
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How accurate this is, of course, is another question: with the gas boiler there are certainly losses during combustion and the power consumption of the pumps is not accounted for, and with the heat pump I believe the heat amount is calculated and not measured. In short, there will probably be a certain margin of inaccuracy.

Not entirely correct. The calculation on the gas bill simply compensates for different pressures in the gas supply systems and slightly different gas compositions. In other words, in network A the pressure is slightly higher for some reason, and the gas has a slightly different composition than in network B.

A condensing boiler has efficiencies beyond 100% (yes, no typo, this is due to the old definition of the calorific value), so it produces about 1.0x kWh of heat in the house from 1 kWh of gas. The exhaust gas losses are already deducted.

Pump electricity consumption is of course added on top; this also applies to the heat pump and is NOT included in the seasonal performance factor (SPF).

Best regards,

Andreas

andimann schrieb:

Not entirely correct. The calculation on the gas bill simply compensates for different pressures in the gas supply systems and slightly varying gas compositions. For example, the pressure in network A is slightly higher for whatever reason, and the gas composition differs a bit compared to network B.

I understand, I just thought that the different pressures and compositions are normalized to kWh of thermal energy using the z-factor in my example. That is, there are regionally different z-factors, but the thermal energy should still be comparable in the end (mainly for billing purposes).

andimann schrieb:

A condensing boiler achieves efficiencies beyond 100% (yes, no typo—that is due to the old definition of calorific value), meaning it converts 1 kWh of gas into approximately 1.0x kWh of heat inside the house. Flue gas losses are already deducted here.

Of course, the power consumption of the pump is added on top, but that also applies to heat pumps; it is NOT included in the seasonal performance factor either.

Yes, I’m familiar with the 115% efficiencies (we switched to condensing boilers back then, and it was noticeable). The question is whether the amount of heat contained in gas can actually be equated with the heat output calculated for the heat pump. My metrology background says “No.” I just don’t know how large that margin of error is.

I hadn’t realized the seasonal performance factor excludes pump power before, but it makes sense when determining the efficiency of heat generation. The only disadvantage is when the heating demand is very low, so the pump’s power consumption disproportionately affects the total heat pump energy use. But that applies equally to gas as well.

Hello,

Hangman schrieb:

Sure, I just understood it as different pressures and composition being normalized to kWh of heat energy in my example via the z-factor.

If I understand correctly, the compressibility factor represents the different pressures, while the calorific value accounts for the gas composition.

In other words, the compressibility factor first normalizes to a standard pressure, and the calorific value normalizes to a certain reference gas.

This results in the delivered kWh of energy in the end. What your gas boiler then does with it is another matter.

Best regards,

Andreas

If you want to know precisely, you need to integrate heat meters. That way, you know exactly how much energy has been delivered to the house.