This is just my own experience and not verified anywhere else that I know of. Your solar cover is certainly the best option for reducing evaporation.
In summer, I've used my own homebrew liquid cover and so far I've seen only 13% reduced evaporation in an outdoor pool (see test details below).
I use some other stuff during winter that knocks evaporation back way more - nearly 60% reduction. I don't know if it's available over there, but it's called Aquatain here. It's used in water reservoirs, and is silicone-based. Unfortunately it's attracted to plastic (plasticaphyllic? haha), so it's not suited for summer and pool toys, but doesn't grab onto the waterline tile. It does leave a ring in the skimmer box, and you can detect it, if you know the feel of silicone, on a cleaner hose or robot cord. It becomes completely undetectable on everything after 7 to 14 days.
Swimmers do not detect either liquid cover. I haven't noticed any difference in filtration. Theoretically, there might be a slowing of pH rise, but I haven't detected it, nor any other effects on pool water chemistry.
Cheers
Test detail:
Cetyl alcohol cover - I only have 2 reps for cover v. no cover so far. Each rep is a period of 4-5 days, compared to closest local pan evaporation numbers for the same period, to assure both covered and uncovered periods are subject to a similar environment. Pan evap for the covered period was higher, so the reduction of evaporation may have been higher. Only more reps can answer, and I was going to do at least 4 more reps before talking about this, but I realize what a pain humidity can be indoors!
If you want to try it for yourself, I tried 5 or 6 different recipes, and the best for me is 3.5 ounces rubbing alcohol and one teaspoon volume of cetyl alcohol, available from a DIY cosmetics supplier. The cetyl alcohol I got is little 1/8" prills (little solid flattened balls). Leave it to dissolve overnight and shake it like crazy before using, every time you use it. I use a sauce bottle (ketchup squeeze bottle). Pour around an ounce to ounce and a half, once a week, and see if you like it.
To the best of my knowledge, cetyl alcohol can be derived from (e.g.) coconuts or synthesized, and is used in hair conditioner and cosmetics. After a career including pesticides, I'm very careful with chems and exposure risks, and I'm not the least bit concerned about either ingredient used this way. If you look hard, or in just the right light, you will detect it on the surface just after putting it on and you will probably smell the rubbing alcohol as it dissipates. The rubbing alcohol (aka IPA, aka isopropyl alcohol, not aka India pale ale!) is working as a solvent and dispersant which evaporates pretty fast just after application, so you might want to be ventilating your pool room at that time. You might see some bright white 1/8" globs dancing around the skimmer box the first day. It's much harder to detect the next day, but in just the right light, you can see it. I suspect you could also get 10 kids to lather up with sunscreen, which seems to be a similar effect!
It completely disappears after about 5 to 7 days in my outdoor pool, but maybe it would last a little longer indoors, I have no idea. I use about 3/4 ounce on my 12K pool, 5 to 7 days apart. There are commercial products available which use these ingredients, and also sometimes steryl alcohol and calcium hydroxide, reasonably benign chems from a human exposure perspective.
Silicone based cover - I have 5 replicates, tested similarly. The total of all reps have very similar total pan evap. I wouldn't hesitate to recommend this for an open winter pool with no pool toys, subject to warning that the scum line inside a plastic skimmer box is alarming at first, until it finds it's way back onto the water. You can easily just wipe it out if it bothers you, but i think its acting as a reserve until you can't detect it anymore.
Testing is SLOW!!! I often start a test period, only to be shut out by rain. Or two comparable periods don't get similar swimming. Hoping to do some more summer testing this year, but I'm satisfied that the silicone-based cover, despite its price, pays off for me in winter, so I've quit testing. The summer stuff is cheap as chips.
