electricity Meter

I think that the current government changed this; one is now charged the maximum rate for day, night and weekends usage. It might also depend on which electricity company you are with.

We looked into this and could not see any benefit for us.
You have to pay for the installation so, unless you are here long term you are unlikely to see any savings.
Obviously the greatest benefit is for those who are out of the house during working hours Mon-Fri. Whilst usage is cheaper overnight and at weekends with the two meter system, it is dearer during the day - no benefit for us as we are retired.
Also, if you are renting, you have to get the owner's permission and they will not be interesting in helping with the cost of something which is going to save money for their tenant but not for them.

It is only worth having a "bi-horaire" meter if you use the majority of your electricity at night - timer-controlled water heating for example. If a new apartment is only equipped with a simple meter, it was almost certainly anticipated that that was the most efficient arrangement.

Note that you have to pay more for daytime electricity if you have a bi-horaire meter - and that you have to pay to have it installed.

If you don't own the apartment it is probably not worth installing a meter bi-horaire. If you do own the apartment the value probably depends on your electricity use. It is definitely worth while for us. The big user of electricity is probably your washer, dryer and dishwasher. Drying clothes or heating water require a lot of energy. We only use the dryer, washer and dishwasher after 10 pm or on the weekend. Last year we used approximately the same amount of electricity on both meters. The cost saving was significant. If you own an apartment or house and will likely be there for an extended time I would definitely recommend two meters. Check with your electricity provider for the actual cost of electricity on each of the meters.