Air-water heat pump: Indoor or outdoor installation?

We are planning an air-to-water heat pump for a new building. My questions:

1. Indoor or outdoor installation of the air-to-water heat pump, which is more economical or efficient?

2. Besides the monoblock units, there are also so-called split units. Which variant is more economical in the long term?

1. These things always need outside air. With split systems, only part of it comes inside. There are heat pumps for indoor use for hot water, but as far as I know not for heating.

2. Monoblock.

There are efficient and less efficient devices here and there. Good monoblock devices are available starting at about 3000 EUR (5kW Panasonic) if you buy it yourself (+ installation + hydraulics with hot water storage). Another advantage: simple installation, no annual climate maintenance, possible to do it yourself. Replacement at the end of the service life then costs only about 3000 EUR + 2-3 hours for a technician and not 10-20k EUR. Have fun calculating.

For efficiency, planning the surface heating and later the optimal mode of operation are at least as important as the device itself.

Of course, there are complete units for indoor installation. So far, I am very satisfied with them...

Ashes on my head, yes that's true - outside air is then directed inside.