We live in a single family house. I want to install a couple of outlets that I can use for holiday lighting etc. in the front side of the house.
Complexity and cost will vary wildly on where existing power runs in the house, how your house is wired, where your panel is, etc.
If there's a surplus of 20A circuits running lighting and nothing else, then it's probably fairly straightforward to run outlets off that, but may not do what you want. If the house is somewhat under-wired (quite common), you may not have power to pull from those, because they're servicing a ton of other stuff. My parents house, for instance, had, among other electrical atrocities, the front porch outlets on the same circuit as the master bathroom, upstairs, on the back of the house. I guess GFCI outlets were so expensive that the wire was cheaper, or something...
The question for you experts is, what’s the best way of doing this safely? Can I splice the wiring from 1) the doorbell 2) the front porch light, or 3) the above-garage motion-sensitive light, to create a new outlet? Ideally, I will be able to control this outlet separately with a separate switch.
You probably could, and if all you wanted was a single outlet, that would probably be the way to go (not the doorbell - that's not 120VAC, for very good reasons).
But if you want it run with a switch, it's probably just as easy to run a new 20A circuit from the panel. How much that costs... depends, as noted.
Tapping existing lighting circuits, then adding a switch, is the sort of thing that will make future owners of the house wonder what you were smoking, though. Switched outdoor outlets, in general, are pretty absurd in the first place.
