Thanks glort, I was not aware of the term "zero export".
I ran the numbers some time ago and the outcome is not very exciting.
However, I have these panels sitting on a shelf doing nothing at the moment.
This would be a "winter only" application with the panels almost in a vertical orientation and facing due south (for north American orientation).
The big problem is the cost of a "zero export" inverter rated at 3kw.
This system would NEVER pay for itself in 30 years when contributing only in winter.
(In summer the power usage is almost zero at this site so no need for solar).
I suppose the best application for spare panels is to heat a domestic hot water tank on a year round basis.
I can easily match the impedance of an element to the best efficiency point of my panels.
I also have an MPPT tracking converter which converts Panel power to a electric element sweet spot.
I bought one of these units a year ago and plan to install it. I is designated for my hot water tank.
https://www.youtube.com/watch?v=YkPtPXfhiYkI think it is meant to achieve what you are working on.
I think you are right, the amount of energy I would produce trying to offset my space heater consumption would not be worth the effort.
Keep us posted on your water heating project. This is something where PV panels can really do well.
I have several water heating applications that would benefit from solar so if you come up with a good DIY solution for tracking PV power points it would be very interesting to see it.
22kw of panels ... wow! that's a good sized array you have there mate! That's more than my house uses per day. Which brings up the burning question of excess energy storage. We really only have two options. Store in batteries or store as heat.
Charging a small electric vehicle would be very feaseable with your system.