Hello Christian,
The pool is very quickly raised, is filled in about ten minutes and the temperature rises by 2°C per hour in winter (so more quickly in summer). In summer, with the inflatable cover, the temperature is maintained with the sun and the electricity consumption is really lower. I can't say exactly what the impact is on the electricity bill, but there is obviously an impact.

Oh, we didn't test it in winter, so we dismantled the pool and put it away in the storage room. You shouldn't use it in frosty weather anyway (the pump could freeze), and there was a call to save electricity because of the shortage.

The statement about the 2 degrees per hour is roughly correct when the filling is between the min. and max. lines. When the sun is shining and it is warm, it goes a little faster. The temperature is comfortable for us at 37 degrees. So if the water is 17 degrees, for example after filling with cold water or a spring night, it takes about 10 -12 hours at 2 kw power input. So 20-24 kwh are needed for heating. On a spring night with temperatures around 10 degrees, the temperature drops about 10 degrees until the next morning. For infrequent use, the amounts are manageable (especially if it saves a visit to a spa), but if daily use occurs, it becomes expensive unless you have a PV system. For refilling, depending on the hot water generator, (partial) filling from the hot water storage tank of the house can be worthwhile if the pool is then to be used promptly and if the storage tank is large enough.