As the release date of Horizon Forbidden WestSony made it preload available for PS5 and PS4thus revealing the download size of version 1.003.000.
As PlayStation Game Size reports, the preload size of the European version of Horizon Forbidden West is 98,074 GB for PS5 and 90,243 GB for PS4. To these are added 1,647 GB for buyers of the Digital Deluxe and possibly the day one patch (if it is not already integrated in the 1.003.000 version).
However if you have purchased one digital copy for PS4 and then later upgrade to PS5 (which is logical since it costs less and the upgrade is free), keep in mind that the preload will allow you to download only the old gen version, while for the PS5 you will have to wait for the stroke midnight on February 18, 2022, which is the day of the launch of Horizon Forbidden West.
To pass the wait, you can read about all the many options for accessibility and customizable difficulty unveiled yesterday by Guerrilla Games or admire the ferocious Tremortusk in action on PS4.