Attic renovation with air conditioning for heating and cooling?

Hello,
our planning for the attic conversion and renovation is progressing further.
Now we are faced with the question of whether we should treat ourselves to the luxury of an air conditioning system (for heating and cooling) or keep it old-fashioned (like the rest of the house) and only heat with radiators?
Our house is exposed to direct sunlight all day (at least 12 hours).
In last year's record heat summer, the apartment was continuously at least 25 degrees Celsius, even though we of course ventilated accordingly in the mornings and at night and kept windows and blinds closed as soon as it got warm.
The additional cost for an air conditioning system compared to a "normal heating system" would be around 5000 euros.
The electricity costs are said to remain reasonable thanks to the modern technology and the new insulation.
Has anyone here had personal experience or is currently considering this?
Thanks in advance.
Regards
Stephan

Heating with air conditioning seems expensive to me. I would plan both heating and air conditioning. Our new house will also have air conditioning for the bedrooms, after we had around 30 degrees inside last summer. And there are supposed to be even more hot summers to come.