Every modern system comes with monitoring built in — your inverter's own app or web portal (for example the Solis app/cloud, or the integrated apps that ship with the newer all-in-one systems) shows you generation, what you're using, what's going into the battery and what's being exported. That's the first place to look, and for most people it's enough to see day-to-day that everything's working and to spot a fault if production suddenly drops.
There are two things worth adding. First, if you want trustworthy export figures rather than estimates, a Shelly CT clamp (a small current sensor on your meter tails) gives you an independent, accurate read of what's actually flowing to and from the grid — that's aged well as cheap, reliable advice and it's increasingly popular. Second, the more technically-minded now feed their data into Home Assistant, which lets you combine inverter, battery and clamp data on one dashboard and — importantly in 2026 — automate against time-of-use or dynamic prices, triggering battery and EV charging in the cheapest half-hours.
The newer integrated systems bundle their own monitoring-and-optimisation apps that try to do a lot of this automatically, so if you've gone that route you may not need to build anything yourself. If you're on a value inverter-plus-battery combo and you enjoy tinkering, the Shelly-plus-Home-Assistant route is the powerful, flexible option. Either way, check the app in the first weeks after install to confirm generation matches what you were promised — that's when monitoring earns its keep.