I do not think anyone can answer that, because you do not have the system nailed down.
Not sure how you came up with 3KW of generation.
Imagine: Cold night out, so you get a blanket and watch a DVD (25W DVD, 100W TV). OK.
Furnace kicks on (1/4HP with a 420W draw, 1700W surge). Still OK.
Grab a beer from the fridge (40W bulb). Fine.
Flush. Well pump, and surge. Uh oh. Getting pretty close.
And then the fridge thermostat realizes it is time to kick on (1500W surge).
Not OK.
Hydro is great, and 3KW 24/7 is a whole lot of power.
But 3KW max limit at any time is not much at all.
If it was me, I'd have some battery. Or grid tie.
If I could actually get 3KW 24/7, I'd probably be off grid.
Unless they made grid tie much more appealing than it was last I checked, which I think they did.
Grid tie would probably be worth looking at adding some solar since most of the expensive stuff would already be dealt with. Then solar is gravy?
Other things to consider for nailing down the system.
Heat. A battery with a 3KW dump load sounds like a pain? 3KW heats a lot of water. Those old electric space heaters are like 1500W, and 2 of them running all night would be a lot of heat.
'Car alternators' insinuates 12V. 3000W at 12V is 215A? #000 copper is rated about 240A.
And the wire losses would be high. #000 (#3/0) carrying 215A 500' loses 5700W, nearly double what you want to make.
Even #0000 (#4/0) copper running 50' with 215A wastes 2265W, or 75% of what you want to make.
Watts is Watts, and 746W is 1HP. HP can be converted to torque, and torque ruins bearings.
A 250A car alternator at 14V is 3500W, 4.7HP of output.
The force on the bearings is 4.7HP, plus losses whatever they are, but I expect it's less than (way less than) 50% efficient at 3500W, so those little bearings are being subjected, 24/7, to 10HP or more.
If you can get 3KW 24/7,
you probably want to go 48V with a battery system,
more for a grid tie.
G-