Economic analysis of heat pump/ice storage/photovoltaics

2025-10-28 09:36:03

Hello everyone,

I have a single-family house (built in 2018) with underfloor heating, which is operated with gas. I am considering carrying out a personal "energy transition" in the long term. My question would be whether and when it pays off.

Currently, I pay around €5,000 per year to the municipal utilities for gas (11,600 kWh/year) & electricity (3,600 kWh/year). About two years ago, I received an offer for a photovoltaic system (22.62 kWp, east/west orientation) including a storage system (9.6 kWh). At that time, the solution cost around €25,000. Do you have any experience with when such a system becomes worthwhile? I would like to do the calculation myself (via Excel).

The problem is certainly more or less replacing the heating or gas. Has anyone had experience with ice storage systems? Are there better alternatives?

Thank you very much for your help!

2025-10-28 09:49:15

Currently, I pay around €5,000 per year for gas (11,600 kWh/year) & electricity (3,600 kWh/year) at the municipal utility company.

Crazy! 11,600 kWh of gas normally costs about €1,000 per year and 3,600 kWh of electricity about €1,300 per year.
Something is wrong with your price.

The problem is certainly more or less replacing the heating or the gas.

No, the problem is your kWh price or a wrong calculation.

Has anyone had experience with ice storage? Are there better alternatives?

Practically everything in a normal single-family house is better. For a building year 2018, the only right (financial) solution is to stay with gas. Gas can’t get so expensive that you recover the cost of a new heating system through lower heating costs.

2025-10-28 09:57:25

Hi, unfortunately this topic is quite overdiscussed and quickly attracts trolls and ideologists of all kinds. My insight is: The result of a cost-effectiveness analysis depends significantly on the assumptions made about future developments. Seen this way, you can always get exactly the outcome you want. For your case, the following advice/recommendation: 1. Do not mix technical equipment. Consider PV and heating separately. Ordinary PV systems do not produce nearly enough electricity in winter to operate heat pumps effectively. 2. If your heating system is not already broken, do not replace it. 3. If your consumption (kWh) is correct, you don’t have a huge problem and can later switch to a standard air/water heat pump without issues when technically necessary (ice storage is completely unnecessary for you and makes the matter more expensive and complicated unnecessarily). 4. PV should now be cheaper because prices for modules and storage have fallen and craftsmen no longer have waiting lists of several months to over a year. On the other hand, the gas crisis might cause a shift in subsidy conditions. It could be that VAT exemption and feed-in tariffs will soon be discontinued.

2025-10-28 10:11:22

Crazy! 11,600 kWh of gas usually costs around €1,000 per year and 3,600 kWh of electricity about €1,300 per year.
Something is wrong with your price.
No, the problem is your kWh price or a wrong calculation.

I looked up my bill from last year again. I pay 38.59 ct/kWh, is it 36.1 ct/kWh for you as described above? The gas price for me is 13.88 ct/kWh. I am probably 2 to 4 ct/kWh higher... which provider do you have?

2025-10-28 10:18:35

Hi,
unfortunately this topic has been talked to death and quickly attracts trolls and ideologues of all kinds.
My conclusion is: The result of a profitability analysis depends significantly on the underlying assumptions about future developments. Viewed this way, it can always turn out exactly as you want.
For your case, the following advice/recommendation:
1. Do not mix technical equipment. Consider PV and heating separately. Normal PV systems do not produce nearly enough electricity in winter to operate heat pumps effectively.
2. If your heating system is not already broken, do not replace it.
3. If your consumption (kWh) is correct, you do not have such a huge problem and can later switch to a normal air/water heat pump without difficulty when technically necessary (ice storage is completely unnecessary for you and unnecessarily increases cost and complexity).
4. PV should now be cheaper because the prices for modules and storage have fallen, and craftsmen no longer have waiting lists of several months to over a year. On the other hand, a turnaround in funding conditions threatens with the Gas Kathi. It could be that VAT exemption and feed-in remuneration will soon be dropped.

Then I will hold my tongue for now. In my opinion, the profitability analysis should be calculated very conservatively. Have you ever created such an analysis?

2025-10-28 10:19:30

I dug up my billing from last year again. I pay 38.59 Ct/kWh, is it 36.1 Ct/kWh for you as described above? The gas price for me is 13.88 Ct/kWh. Apparently, I’m 2 to 4 Ct/kWh higher... which provider do you have?

I have a heat pump and therefore only electricity. Currently about 26 cents. The numbers mentioned were simply generously estimated based on market data. How do you then come to €5,000 per year? Consumption alone without basic fees is only about €3,000 for you – there is still a lot of potential there (Check24 & Co). Much more than with converting to a new heating system. If you might save 200 to 300 € per year due to a more efficient heating system, you can calculate yourself when the ice storage with costs of €30,000 pays off... which is never. PV is another topic. That must be calculated separately and individually. My conclusion: look for new providers. In parallel, you can have a PV system designed and calculate individually whether and how it pays off.

Economic analysis of heat pump/ice storage/photovoltaics

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