(This is my first post in this community, hoping it's the right place)

I'm looking for a simple way to prevent a 2kW house water heater to draw too much current at once. Mostly because solar power seldom can provide that much (and the rest is taken from the grid). 300W would be perfect for me. Of course I would couple it with a timer to draw only when power is available

I suppose there exists a simple device for that. Connected if possible. No luck in finding it online though.

And I'm also interested in any theoretic insights on how such a device will work, and its limitations (eg. if several loads are connected).