On generators, since that is the usual answer and the sizing catches people out.
A well pump has a large starting surge. It draws several times its running figure for a moment at start-up, and a generator that comfortably handles the running load can stall on the start. This is the single most common mistake, people size for the number on the pump plate and find it will not start.
So:
Find your pump's actual specification, and size for the starting draw rather than the running one. If you cannot find the numbers, an electrician or the well company can tell you in a phone call.
Decide how it connects before you buy anything. A pump is generally hard-wired, so you cannot simply run an extension lead to it. That means either a proper transfer switch installed by an electrician, or an inlet with an interlock. This is the part that costs money and it is not optional, backfeeding a house without a transfer switch is dangerous to line workers and to you.
You do not need to run the whole house. Pump, fridge and a couple of circuits is a much smaller and cheaper machine than one that runs everything. Many people run the pump for twenty minutes twice a day, fill containers, and turn it off.
That last pattern is worth planning around: you are refilling storage, not living normally on generator power.