A Guarantee of Origin / I-REC certificate is issued per MWh a renewable plant generates, and can be redeemed against any MWh of demand anywhere in the same accounting year — timing never has to match:
Annual match = min(1, ΣG(t) / ΣD(t)) for t = 1..24 h
That single yearly ratio can read 100% "renewable" even though the grid burns fossil power every single evening, because a sunny noon's surplus certificate quietly cancels out a windless night's deficit on paper. Real-time ("24/7 carbon-free energy") matching instead requires each hour to clear on its own:
Hourly match = (1/24) Σ 1[ G(t) ≥ D(t) ]
G(t) = Solar(t) + Wind(t), Solar(t) = Cap_solar · max(0, sin(π·(t-6)/12)) for 6h ≤ t ≤ 18h
This 2D view renders the same 24 hours as a clock face instead of a bar row: each hour is a wedge whose length is that hour's generation, colour-coded green/red by whether it clears its own hour, with a grey tick marking the demand level to compare against. Below the clock, a running ledger line plots the cumulative generation-minus-demand balance across the day — the exact quantity an annual certificate scheme is implicitly "banking": the line can dive deep into deficit (shaded red) for hours at a time and still finish the day at or above zero, which is precisely how an annual match can read 100% while individual hours fail.
- Annual (GO/I-REC) — every wedge turns the same colour, based only on whether the year-end ledger balance clears — hiding the hour-by-hour reality.
- 24/7 Hourly — each wedge is judged on its own; red wedges are hours a "100%-renewable-certified" grid still ran on fossil backup.
- Solar / Wind capacity — reshape the generation curve; solar is a fixed noon-centred bell, wind is noisy and can blow at night.
- Re-roll wind weather — wind is intermittent by nature; this redraws a fresh (but still physically smoothed) hourly wind trace.
- Play day cycle — sweeps a radial time cursor and sun marker around the clock, and a matching cursor along the ledger, so you can watch the balance rise and fall in real time.
This is the exact critique behind Google's, Microsoft's and the EnergyTag standard's push for 24/7 hourly-matched carbon-free energy, as opposed to the older annual unbundled REC/GO/I-REC market.