House purchase built in 1995 vs. new construction long-term cost calculation

Hello dear forum participants,
after a long time of silently reading along, I would now like to ask for advice.
My "better" half and I, both in our early 30s, no children (one planned) have the option to buy a single-family house:
Income situation both still full-time: He: 3700 euros net (civil servant), She: 2500 euros net (public service) = Total: 6200 euros net

Property data:
- Purchase price: 375,000 euros, unfortunately not negotiable
- Year built: 1995, solid 36.5 cm
- detached, plot size: 770 m2, corner plot with village edge location
- Living area: 120 sqm
- fully basemented, solid garage (with access to the basement)
- oil heating from 1995, 2020: burner new
- windows from 1995: wood with double glazing (good condition)
- energy certificate (based on consumption): E with 155 kwh/m2
- top floor ceiling insulated
- tiled stove in living room present
- underfloor heating in guest WC and main bathroom present, otherwise radiators from 1995 everywhere

Purchase price: 375,000 euros + incidental costs (without broker) = 396,000 euros
Equity capital: 170,000 euros
Loan amount: 225,000 euros
Annuity over: 20 years: 1300 euros

Investments directly after purchase from equity overall: 40,000 euros
- new kitchen: 25,000 euros
- additional prefabricated garage for one car: 15,000 euros

Costs that, in my opinion, will be incurred in the next years: 90,000 euros
- Heating (heat pump + photovoltaics or pellet heating with solar thermal): approx. 60,000 euros
- Windows: 15,000 euros
- Renovation main bathroom: 15,000 euros

Total costs: 530,000 euros

In contrast, I now present the price of a new building, at the conditions I inquired about from three regional construction companies:

- Costs for a two-story city villa (without basement) with 170 sqm living space including plot in the region: 700,000 euros
- Building construction costs (floor, painting in EL) including incidental costs: approx. 480,000 euros
- Double finished garage: 35,000 euros
- Kitchen: 25,000 euros
- Fireplace for living room (small, only for the sight of the fire): 5,000 - 10,000 euros
- Outdoor facilities: 25,000 euros
- Photovoltaics + electricity storage: 25,000 euros
- Land prices in the region: approx. 110 euros / sqm: approx. 90,000 euros land costs for 800 sqm
- Loan amount: 480,000 euros, rate: 2,500 euros for 30 years

Pros of existing house:
- very well maintained overall condition: facade, windows, roof beams newly painted 2019, sanitary facilities in main bathroom renewed 2021 (shower, double washbasin, WC)
- parquet floor in living/dining room and hallway on upper floor
- location of the house with southwest terrace, personally ideal for me, west side of the plot = field with wide view for beautiful sunsets on the terrace
- well-kept garden, which cannot be seen from outside in summer
- tiled stove
- access to garage through basement
- property is in the desired location, parents within walking distance, circle of friends here, daycare, primary school, supermarket available.

Cons of existing house:
- energetic renovation necessary, see above
- no underfloor heating on the entire ground floor, only in the main bathroom and guest WC, which makes future conversion to a heat pump more difficult.
- 120 sqm are actually too small in my opinion or a room is missing. Ideally, two offices, one each for me (necessary for the job) and for my better half (2 days home office per week).
- Dormer slopes with standard knee wall
- Basement rooms without heating/insulation, currently one room is used as a party cellar with Swedish stove. Conversion to office possible but expensive. Windows in the basement can be retrofitted relatively easily as the house is on a slope.

Pros of new building:
- exactly the size with desired floor plan and number of rooms
- no dormer slopes
- new and efficient, monthly incidental costs for heating/hot water/electricity approx. 300 euros lower

Cons of new building:
- additional costs
- garden facilities logically not present
- no basement for storage/workshop

The question now is what makes more sense in the long term. If you notice any major errors in my explanations, please correct me.

And please excuse the long post, I just tried to describe the situation as well as possible.

Many thanks and best regards

Martin

Without looking at the floor plans in detail now, with the price difference I would tend to go for the existing property and gradually renovate certain things by myself. Building a house always costs more than planned, realistically you probably have a difference of 200k rather than 170k. I see it as more critical if the number of rooms does not fit. Then better to look for another property.

You will not want to operate the existing house with a heat pump without insulation. The costs for windows and the main bathroom are probably too low.

With the new build option, you have a double burden during the construction phase that you would not have with the existing purchase. Please take this into account.

Thanks already for the feedback. I also tend to prefer the existing house. According to the local construction companies, one unfortunately cannot count on significantly decreasing construction prices here. Unfortunately, I also only see falling interest rates again in 2025, or never....

Option three would be to buy the house we are currently living in rent-free. (House of grandpa, who passed away last year. Unfortunately, we are not heirs. The heirs understandably want to sell the house. So we either have to move out this year or buy it ourselves.)
Built in 1968, multi-family house, 3 times 70 sqm apartments stacked on top of each other, with a proper staircase. We occupy the upper two.
Purchase price without additional costs, as passed on within the family: 170,000 euros
Complete renovation costs according to the architect: 330,000 euros
Problem: Location is very poor. The house shades our own property/garden all day. No terrace, no access to the garden from the lower apartment, annoying neighbors with ill-behaved and constantly barking dog.

You will not want to operate the existing house with a heat pump without insulation. The costs for windows and the main bathroom are probably too low. In the new building option, you have a double burden during the construction phase, which you would not have when purchasing an existing property. Please take this into account.

15000 euros for the bathroom are too low??? We paid that for two bathrooms.

Without looking at the floor plans in detail now, at that price difference I would tend to choose the existing property and gradually renovate certain things by myself. Building a house always costs more than planned, realistically you probably have more like a 200k difference rather than 170k. I see it as more critical if the number of rooms doesn’t fit. Then better to look for another property.

The rooms themselves would just be enough. If there remains only one child as planned ;). For that, you then sacrifice the dressing room. Or you just have to convert the party basement into an office. I always also eye the saved 200k, which could be well invested in travel. Over the next 10-15 years. Thanks anyway for the feedback.