Hello,
When choosing the right cross-section of the conductor, one should take into account not only the load power (as mentioned in previous posts), but also, among others, cable length, cable routing, number of cores in the cable / cable, number of cables run together, type of cable insulation (due to thermal conditions), protection operating conditions, mechanical stresses to which cables may be exposed, etc. the installation not only supplied energy to the receivers, but above all, that it was SAFE for the user. The main issue is to ensure the correct operation of protection devices (most often overcurrent and residual current devices) and hence the requirement for a cross-section of at least 2.5mm2 Cu, so as to ensure a low value of the short-circuit loop impedance and the reliability of the circuit continuity (mechanical strength).
This is what the regulations in force in Poland say (for several years now). Conclusion: for lighting 1.5mm2 Cu or more, for plug sockets 2.5mm2 or more.
Arguments such as "I use 1.5mm2 cables because it is difficult to attach the socket in the wall with 2.5mm2 cables", or that "the kettle has a cable for a 3x1.5mm2 socket" are simply funny and testify to the ignorance of the writers, but I know that people approach differently to regulations, projects, etc. Most try to change something, save something, make work easier, etc., but later in the media we hear again that another apartment (sometimes even together with the residents) burned down due to "faulty electrical wiring ..."
I do not comment on the solutions proposed and used by "electricity experts" because it is a waste of time.
best regards
Peter
ps how much PLN can you save by using 1.5mm2 cables instead of 2.5mm2? is it really worth doing?