Hourly Clean-Energy Matching: Do Green Certificates Cover Every Hour?

Matching Method

Generation Fleet

Solar capacity 60 MW

Wind capacity 40 MW

Grid demand scale 100%

Live Readouts

Annual match (GO/I-REC)

Hourly match (24/7 CFE)

Fossil-covered hours despite a "100% renewable" certificate

0 / 24 h

Legend

Demand bar (this hour's load) Generation ≥ demand this hour Generation short — fossil backup fires Sun position (daylight hours)

How it works

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

Annual (GO/I-REC) — bars turn green whenever the yearly total clears, hiding the hour-by-hour reality.
24/7 Hourly — each hour is judged on its own; red bars 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 time cursor and sun marker across the 24 hours so you can watch the gap open and close 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.

Hour 12:00 · Demand — · Gen —

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