elyob
I bolted a seventh 100W panel onto the array this week — £55.24 from Photonic Universe, plus £7.99 for a single mounting bracket. Total upgrade cost: £63.23. The array is now 700W, up from 600W.
The original six panels have been comfortably hitting 600W on cool, bright days, occasionally clipping above nameplate at 692W. There's no headroom there — once the MPPT saturates, anything beyond it is left on the panels. The seventh panel buys back the dim-day shoulders: early morning, late afternoon, and overcast hours where I was leaking watts I'd otherwise capture.
The maths is friendly. At a typical 12p/kWh of saved electricity, £63 of panel pays for itself once it's pushed about 525 kWh through the system. The other six are tracking at roughly 700–800 kWh/year between them, so a 17% capacity uplift means this one should pay back in well under a year — probably by autumn. Anything after that is gravy.
The mount is a salvaged pallet plank, two angle brackets and four bolts — same recipe as the rest of the array. The whole install took twenty minutes. The ROI calculator and the charge planner already know about the new panel; lifetime totals on the dashboard will start drifting upward from today.
What I'll Be Watching
Rather than guess the gain, here's what I'll be tracking over the next few weeks to find out what the seventh panel is actually doing:
- Dim-day shoulder hours — does production start earlier and end later than the same days in 2025? That's where this panel earns its keep.
- Daily kWh vs the 6-panel baseline — comparing April–May 2026 daily output against the same dates last year, with a rough cloud-cover correction.
- Peak-day clipping — the MPPT caps around 720W. With 700W of panels now wired in, summer afternoons should plateau there for longer than they used to. Watching how often that happens tells me how much (if any) of the new panel is being thrown away at midday.
- Payback on the £63 — once the panel has pushed ~525 kWh through the system at the prevailing saved-rate, it's paid back. The ROI page tracks this automatically.
I'll come back to this post in a few weeks with the numbers.