Where can I find maximum generation figures?

Good Morning all, I suspect my panels are not generating what they should, on the odd sunny days we had on the last mini heat wave without a cloud in the sky and south facing panels my generation was 4.5kw max of a potential 5.9kw . I haven't been looking very often at generation so not sure if this issue has been long standing. I'm sure one of you out there has the answers to help so that I can go to my installers if there is an issue or if a simple fix is in order . Regards Gareth

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gareth0898 on a hot day your panels dont perform at best efficiency, you need a cool sunny day for that.
4.5 vs 5.9 seems quite good.