⚡ What is EDF FreePhase?

The simple version

Each day, EDF splits your electricity into three fixed time bands:

Band	Times
🟢 Green	23:00 – 06:00
🟠 Amber	06:00 – 16:00 and 19:00 – 23:00
🔴 Red	16:00 – 19:00

The band names aren't a strict price ranking though — amber has often priced cheaper than green, especially through summer 2026 — so don't assume green is always your best rate. What genuinely matters is whether a slot is free: EDF describes this as happening when wholesale electricity prices go negative — usually because there's more wind and solar power on the grid than the country needs at that moment. When that happens, that half-hour is free: whatever you use costs you nothing. (The separate Government Discount, from 1 April 2026, is a flat 3.5p/kWh reduction applied to your normal unit rate — it isn't what triggers a free period.)

FPRates predicts these free hours each morning by watching the same wholesale market EDF's own pricing is built from — often hours before EDF publishes their official rates.

The technical version

EDF's FreePhase rate for each half-hour slot is calculated from the day-ahead wholesale electricity price (from the N2EX auction) using a formula we've reverse-engineered and confirmed accurate to within 0.01p of EDF's own published rates:

rate = 1.05 × (C × W + P) − GD

• W — the day-ahead wholesale price (£/MWh)
• C — a regional multiplier (2.08 for the North West)
• P — a peak-time adder, applied only 4pm–7pm
• GD — a flat Government Discount (3.5p from 1 April 2026)
• 1.05 — VAT (drops to 1.00 from 1 October 2026)

When wholesale prices are negative, the formula produces a 0p rate for those hours — that's genuinely free hours, driven entirely by the real wholesale market, not a promotion.

How does it compare to Agile Octopus?

A common question on tariff forums is whether FreePhase or Agile gives you more free electricity. We can answer this properly, because we bank real published rates from both tariffs, half-hour by half-hour.

Comparing real data from 2025-10-29 to 2026-08-01 — our data starts 2025-10-29, so this isn't a full rolling year yet, it'll keep growing until it is.

	FreePhase	Agile Octopus
All free/zero-rate half-hours	278	286
Wholesale-driven only (promo hours removed)	200	286

This figure strips out known EDF promotional free hours (football, Christmas Day) using real wholesale data to auto-detect them. In the rare case a promo happened to coincide with wholesale already being negative, that slot is still counted as wholesale-driven - so this is a slight upper bound on genuine wholesale-only free hours, not an exact figure.

FreePhase's "all free hours" total includes genuine promotional hours EDF has given away — free football-match hours, Christmas Day — on top of wholesale-driven free hours. Agile has no equivalent promotional mechanism, so every one of its free hours is wholesale alone. Stripping FreePhase's promo hours out gives the fairest like-for-like comparison of how each tariff's underlying pricing mechanism responds to the wholesale market.