In article , Jeffrey J. Kosowsky wrote:

We are about to install several new circuits as we upgrade the
electrical systems in this very old house.

- For "normal" rooms (i.e. not kitchen, bathroom, garage, workshop, or
outdoors), should one go with standard 15A circuits or should one put
in 20A "just in case"?

- Even if you just put in 15A breakers and receptacles now, does it pay
to pull through #12 wire just in case you ever later want to
upgrade?

- How big is the difference in price for wiring (per foot) and for
circuit breakers?

I believe 20A breakers cost nearly enough the same as 15A ones and 12AWG
wire is only a little more expensive than 14AWG.
I strongly recommend to not cheap out. I believe that current code for
new construction permits 15A capability as opposed to 20A only for lines
dedicated to specific loads. As in no outlets, or one outlet (which
should be for a specific load that does not draw more than 15A) plus no
other loads. I could be off a little, but I believe 15A is a "cheap out"
permitted in a few specific instances.

However, I have yet to hear of a code requirement to upgrade existing
15A circuits that were installed when code permitted them. Just have the
breakerbox/fusebox have adequate labeling that the circuits in question
are 15A circuits - especially if there are fuses rather than breakers.

Local building codes may have exceptions - please know the requirements
if you sell your house.

- Don Klipstein )