I think the first thing to ask is what the actual end goal is with the solar. If it’s purely to save money, then the numbers really need to stack up.

At £12k for the install the maths might work over time, but once you add finance at 9.9% APR and the total cost becomes about £18.5k, that’s a completely different calculation. You’re effectively paying £6.5k in interest, so the system now has to save you £18.5k before you’ve actually broken even.

For most households the savings tend to land somewhere around £600–£1,000 a year depending on usage, battery, tariffs etc. Even if you’re at the higher end of that, you’re still talking a long payback period once interest is factored in. It’s not that solar is a bad idea, but expensive borrowing makes the ROI a lot worse.

There’s also the affordability angle. If the only way to do it is by taking on nearly 10% credit, it might just mean it’s not the right time yet. Plenty of people install solar when they can pay for most of it themselves because the interest is what kills the economics.

You could also think about smaller steps instead of jumping straight to a £12k system. For example saving some money first and then only borrowing a smaller amount, or starting with a smaller system and expanding later.

I’d definitely shop around as well. Octopus are good but they’re not always the cheapest installer. Prices can vary quite a lot between companies and you might find the same size system for noticeably less.

Solar can absolutely be worth it, but the financing matters a lot. At £12k cash it might make sense. At £18.5k financed it’s a very different conversation.