[pjc50]

Odd. I paid £5.5k for a 4kW array several years ago, I'd have assumed it was cheaper now. Possibly you hit a "breakpoint" where the non-unit cost got a lot bigger. Maybe permitting? I chose 4kW because that was the largest size that didn't require extra paperwork.

[simonjgreen]

I have just done a 10kW array for £9k. And I'm estimating payback in < 3 years. It has got cheaper :)