Octopus Agile: Turning Half-Hourly Prices Into Savings

Most UK tariffs charge a single unit rate, or at most a cheap-night / expensive-day split like Economy 7. Octopus Agile is different, and it’s worth understanding, because it rewards automation more than almost any tariff in the country. Instead of one or two fixed rates, the price of your electricity changes every half hour, and tomorrow’s 48 prices are published this afternoon.

This guide explains how Agile works, why it’s a great fit for a smart home, and how to capture the savings you can’t realistically chase by hand.

How Octopus Agile works

On a standard tariff you pay one unit rate no matter when you use power. On Octopus Agile, the day is split into 48 half-hour slots, each with its own price that tracks the wholesale market for your region. The prices are VAT-inclusive pence per kWh, and there’s a price cap so a single slot can’t run away from you.

Three things make this different from a normal tariff:

• The price changes every 30 minutes. Tomorrow’s 48 slot prices are published around 4 p.m. the day before, so there’s no fixed schedule to memorise — the cheap and expensive windows move day to day.
• It’s regional. Agile publishes a separate set of prices for each Grid Supply Point region (London, the South East, the North West, and so on), so your prices reflect your part of the grid.
• Prices can go negative. When wholesale prices dip below zero — often on windy nights or sunny middays — Agile can go negative, meaning you’re effectively paid to use electricity. Octopus calls these “Plunge Pricing” events.

That’s the opportunity and the problem in one sentence: the savings are real, but they move every half hour.

Where the savings are

Because the cheapest slots shift day to day, the wins come from reacting to each day’s price curve:

• EV charging during whatever the cheapest overnight stretch happens to be tonight — and, when a negative “plunge” hits, charging then to get paid for it.
• Pre-heating ahead of the expensive 4–7 p.m. teatime peak, so your heat pump or storage heaters coast through the priciest slots.
• Water heating, dishwashers, washing machines, and battery charging timed to the day’s cheapest half-hours and away from the peak.

On a fixed tariff, “cheap” is either always or a fixed overnight window, and a simple timer is enough. On Agile, the best schedule is genuinely different tomorrow than it was today, and it’s carved into 30-minute slices — which is exactly why a static timer leaves money on the table.

How to capture it: by hand vs. automatically

By hand, you’d check tomorrow’s 48 published prices each afternoon, cross-reference the weather, and reprogram your EV charger, heating, and appliances around the cheapest slots — every day. Almost nobody sustains that. And even if you did, you’d still be eyeballing how much pre-heating your home actually needs.

Automatically is the whole point of a tariff like this. Hungry Machines pulls the next day’s half-hourly prices for your region, combines them with tomorrow’s forecast plus a custom model of your home, then builds an optimised schedule each night. It charges the EV in the genuine overnight trough (or during a negative-price plunge), pre-heats just enough to skate past the teatime peak, and times your hot water and battery to the day’s cheapest energy. Then it does it all again tomorrow against tomorrow’s new prices.

Because the plan is rebuilt every night against real prices and a real forecast, it captures the deep troughs and the occasional negative slots that a fixed timer would sail right past.

Common questions

Is Octopus Agile risky?

Your unit rate follows the wholesale market, so an expensive half-hour costs more than it would on a fixed tariff. Agile carries a price cap of 100p/kWh, which bounds the worst case rather than eliminating it, and the genuinely painful periods concentrate in winter weekday evenings — roughly 4 to 7 p.m.

Against that, you get every cheap half-hour in between, and on windy nights those go negative: Octopus pays you to consume. Most of the year the average unit rate sits below the standard variable tariff for households that shift load.

The honest framing is that Agile rewards flexibility and punishes its absence. If you can move an EV charge, a heat pump or a dishwasher out of the evening peak, the volatility works for you. If your consumption is fixed and evening-heavy, a flat tariff is the safer choice.

How is this different from Economy 7 or a fixed tariff?

Economy 7 gives you one cheap block — seven overnight hours — at the same times every night, forever. A fixed tariff gives you one price at all hours. Both are schedules you can learn once.

Agile gives you 48 different prices a day, published around 4 p.m. the afternoon before. There is no block to memorise, because the cheap half-hours move: tonight’s trough might be 2 a.m., tomorrow’s might be 1 p.m. because wind output is high and demand is low.

That difference decides what a good strategy looks like. On Economy 7, a timer set once captures essentially all the available saving. On Agile a fixed timer captures some of it and misses the rest, since it cannot know that tomorrow’s cheapest window moved — or that three half-hours went negative.

Do I need an EV or battery to benefit?

No, though they help most. An EV is close to the ideal load for Agile: large, entirely flexible about when it charges, and needing the same kilowatt-hours either way. Moving a charge into a negative-price window means being paid to fill the car.

But a heat pump or storage heaters capture meaningful savings on their own, because a building holds heat. Warm the house while power is cheap and it coasts through the expensive evening — no hardware purchase required. An immersion heater does the same with hot water.

What actually decides the benefit is how much of your consumption is time-flexible, not which appliances you own. A flat with electric lighting, a laptop and a fridge has very little to shift, and would likely do better on a fixed tariff.

Next steps

Agile’s half-hourly model is the UK cousin of ComEd’s hourly pricing in the US — same idea, finer time slices. If you’d like the wider picture on how variable rates work, start with our guide to time-of-use electricity rates. For the software that turns those prices into a schedule, see our guide to home energy management systems.

To let your home react to Agile’s prices automatically, see how Hungry Machines works and sign up now.