ᐅ Single- or Dual-Rate Meter in New Construction

Normally not. Except if a heat pump is forbidden to be connected to the household electricity supply, then a second meter is mandatory anyway.

Grym schrieb:
Apart from a heat pump on household electricity being prohibited, the second meter is mandatory anyway.

Then you simply choose a different electricity provider.
Or ignore this clause in the terms and conditions.

Baufie schrieb:
I don’t understand that.

Because if the air-to-water heat pump is connected to a different meter than the photovoltaic system, it never makes sense to install a second meter when combining an air-to-water heat pump and photovoltaics.

Or am I missing something?

It's a bit of both. Basically, you're right, unless your household electricity consumption is so high that the photovoltaics become worthwhile. The heating itself can usually be disregarded, but hot water consumption is an interesting factor.

Now I don’t know what to do anymore.

In our apartment, we currently have an electricity consumption of 4500 kWh. Our house will be twice as large, and as described, we will heat with an air-to-water heat pump and have a 9.9 kWp system on the roof.

Which of my contractors should I ask about the best solution for me?

You need to calculate whether a second meter is worthwhile! Only you can do this based on the terms of your electricity provider, especially if they offer discounted electricity rates for heat pumps.

If it’s not worth it, or only just barely, then choose a single-rate meter. Yes, there are electricity providers who exclude the use of heat pumps in their terms and conditions, but there are also thousands of others that don’t care. Ultimately, it’s just a clause in the terms – no claims, no dispute.

The issue of having two separate meters and self-consumption of photovoltaic electricity can be arranged as well; your electrician can help with that. But as I said, you probably won’t want a second meter anyway because it’s usually not cost-effective.

It is always advisable, however, to have a sub-meter for the heat pump so you can monitor its consumption. This meter is independent of your electricity provider, it’s a small device, not officially calibrated, and costs about 30€ (around $30). You will likely get one or two of these anyway (for photovoltaic systems).

In principle, I agree with the previous contributors:
You need to calculate this yourself, using pen and paper and a calculator.

First, clarify the requirements:
- You need a meter for household electricity.
- If you have a photovoltaic system, it may require its own meter (for example, at least as soon as you want to feed electricity back into the grid—this was the case for my in-laws).
- For the air-to-water heat pump, you may also need a separate meter if you want to benefit from a heat pump tariff offered by your electricity provider.

Since we are facing the same considerations, here is my calculation:

- No photovoltaic system
- One meter for household electricity
- Possibly one meter for the air-to-water heat pump

= one or two meters

According to the local utility company, I have the following information:
The “Green Heating Electricity” tariff applies to systems with either combined or separate metering, each with a contract term until [...].

With combined metering, the heating electricity is measured together with household electricity. With separate metering, the heat pump’s electricity consumption is recorded independently of household consumption via a separate dual-tariff meter.

Additionally:
All legally required charges and taxes valid for 2017 are included in the tariffs (valid for consumption points below 100,000 kWh/year). Changes and any additional legal charges and taxes will be passed on accordingly in the respective supply year.

This means:
- Either we have ONE dual-tariff meter (dual = high tariff and low tariff), where different prices apply for high tariff and low tariff periods (assuming that most household electricity is used during high tariff hours, and at night during low tariff hours, only the heating runs);

- Or two separate meters, allowing the air-to-water heat pump to run on the cheaper tariff all day long (i.e., a separate dual-tariff meter for the air-to-water heat pump),
- While household electricity would be billed under a separate tariff.

Here are the prices from our local utility as an example:

Combined metering for heat pump and household electricity together (dual-tariff meter):
Price per kWh high tariff: 16.234 cents (net)
Price per kWh low tariff: 21.634 cents (net)
Annual base charge: €90 net

Separate metering for heat pump only (dual-tariff meter):
Price per kWh high tariff: 16.234 cents (net)
Price per kWh low tariff: 16.234 cents (net)
Annual base charge: €60 net

Separate metering for household electricity only (single-tariff meter):
Price per kWh: 21.234 cents (net)
Annual base charge: €84 net

In summary, for separate metering, the base charges add up to €84 + €60 = €144 net, compared to €90 net for combined metering.
However, with separate metering, the air-to-water heat pump can consume electricity at a cheaper rate during the day (about €0.05 less per kWh).

The question now is: how much electricity does the air-to-water heat pump consume? There are already many threads on this topic in the forum, so please search for that yourself here.
Otherwise, let’s say you need 18,000 kWh (kilowatt hours) of heat annually. Assuming the heat pump has a seasonal performance factor (SPF) of 3, meaning it can generate three kWh of heat from one kWh of electricity in theory.
This means the heat pump consumes 18,000 / 3 = 6,000 kWh of electricity per year.

Now you need to estimate how much electricity the heat pump consumes only at night. Let’s say, for approximation, that the heat pump uses 50% of its electricity at night (low tariff) and 50% during the day (high tariff).

6,000 kWh / 2 = 3,000 kWh
3,000 kWh * €0.05 = €150
— so separate metering would save €150 (net) per year in electricity costs but costs about €50 more for base charges.
Overall, that’s a net "gain" of €100 per year.

If the heat pump only uses 33% of its electricity at night instead of 50%, there would still be a net "gain" of €50 (net).

The cost and installation of an electricity meter vary between roughly €50 and €100 each (keep in mind the topic of smart meters; I’m not very familiar with this yet).
In my opinion, these one-time costs can be neglected since they would be recovered after one or two years.

According to my calculation, separate metering is moderately worthwhile.
My calculation is based on the numbers from our local utility; it may be different for you.
It is also possible that the air-to-water heat pump uses much more electricity than I have calculated, or that my 50% estimate is completely off.

For the calculation to be worthwhile, the savings in electricity price (in my example €0.05) must cover the additional costs (higher or additional base fees plus the one-time costs for installing the appropriate electricity meter).

So, roughly speaking, if a special tariff for the air-to-water heat pump results in €100 extra per year but saves €0.05 per kWh (possibly only at night), then you need to consume at least 100 € / 0.05 € = 2,000 kWh of electricity (within the reduced tariff period, possibly only at night) for it to make sense.

In the end, I think what I have written here is realistic. However, I will still look for concrete experience, both here in the forum and especially among acquaintances, to verify my consumption values.