Determine the running costs for a house

I am currently in the very early planning phase for the construction of our own home and need some help in compiling and estimating the ongoing costs that such a house will bring after construction. Basically, I want to find out how much of our net income will ultimately remain after deducting all ongoing costs, so that we can, for example, pay the loan installments from it.

A few key data points about the planned construction project:
- Passive house (semi-detached house)
- approx. 150m² living space, spread over 2 full floors
- approx. 430m² plot size
- garage
- initially two adults and a newborn, but a second child is planned
- assessment rate (for property tax B) here in the town is currently 471.

Through my own research, I have come up with the following items (figures always converted to one month):
- property tax: max. €37.50 (I called the tax office and was told that the property tax could not be reliably quantified at such an early stage of planning, but I should expect no more than €450/year)
- electricity costs: approx. €150 (it is not so easy to get meaningful figures on electricity consumption of passive houses; on the internet one finds all figures between 4000 and 7000 kWh/year. I decided to calculate with a fairly high 6400 kWh)
- water: about €15 (assuming a consumption of 120m³/year)
- heating: €0 (classic heating system is omitted in a passive house and hot water generation and supplementary heating is usually done electrically. These additional costs are already included in the electricity)
- waste collection: €26
- wastewater: €32
- household insurance: €15 (here I simply used a comparison site on the internet and took the average price with a coverage sum of €100,000)
- building insurance: €25 (similar to household insurance)
- reserves for repairs etc.: €150 (simply the often-cited one euro per square meter)

The following two points are not directly related to the house itself, but in my opinion somehow still belong to the ongoing costs:
- internet + phone + TV: €55
- GEZ (broadcasting fee): €17.50

(I have estimated or rounded the values somewhat generously upwards, if I could not determine them exactly.)

This makes ongoing costs of €523 per month in total. Now my questions to you experts here:
- which ongoing costs have I not yet recorded?
- where have I gone wrong in my calculation and used completely implausible values?

Thanks in advance!

I love lists like that! I wouldn’t know what you forgot.

To the maintenance reserve, I would also add the classic maintenance costs (additionally). Maintenance of the building services, but also mundane things like clearing leaves from the gutter. Of course, this varies in each case and certainly many people simply do it themselves.

Depending on the size of the property and personal standards, one should also allocate a budget for the garden, permanently even after the initial setup.

Residential building insurance: €25 (similar to household contents insurance)

Including or excluding natural hazard insurance?

What about liability insurance? In other words, is property ownership already included in your current one?

Heating: €0 (a conventional heating system is omitted in a passive house, and hot water production and supplementary heating are usually done electrically. These additional costs are already included in the electricity)

No technology that needs maintenance? No controlled residential ventilation? No filters (mats)?

First of all, thanks for the quick replies!

Regarding liability insurance, I will have to convince my wife to hand over the documents of the existing insurance. But thanks for the hint that I should check that.

Regarding natural hazard damage, I am not quite sure yet whether it makes sense for the property we have in mind. But I definitely want to get advice from a professional on that.

In your opinion, should I then better calculate €1.50 per m² for maintenance and repair costs?

Somehow there was already a collection thread this year... maybe go to Search for example [Nebenkosten]

Additional costs finished house