Why the cheapest window shifts every night (and why you need to check)
Agile prices are set by the wholesale electricity market, not by a fixed schedule. Every half hour carries a different price, determined by what's happening on the UK grid at that moment: how much wind is blowing, how much solar is generating, how much demand there is from households and industry.
Overnight, demand drops significantly as businesses close and most people sleep. That pushes prices down. But within the overnight window, prices are not uniform. A night with strong westerly winds across Scotland might see prices fall to 1.5p/kWh at 3am as offshore turbines generate at full capacity. A calmer night might keep overnight prices at 8-12p/kWh throughout.
The cheapest overnight slot on Monday might be 1:00am. On Tuesday it might be 3:30am. On Wednesday, during a wind event, it might be 11:30pm with prices already going negative. There is no single "always cheapest" time. The only way to know tonight's cheapest window is to check tonight's prices.
That's precisely what AgileAlert's live dashboard shows. Every half-hour slot for the next 24 hours, updated as new prices publish.
How to find tonight's cheapest window for EV charging on AgileAlert
The process takes under a minute. Here's the exact routine.
Step 1: Open AgileAlert at around 9pm. Octopus typically publishes prices for the next day by 4-5pm, so the full overnight picture is available by early evening.
Step 2: Look at the price display for the period from 10pm through to 6am the following morning. This is the overnight window where EV charging makes the most financial sense.
Step 3: Identify the lowest price band. AgileAlert colour-codes prices so the cheapest slots are immediately visible. Look for the green or lowest-colour cluster within the overnight hours.
Step 4: Note the start time of that cheapest block. If the lowest prices run from 2:00am to 4:30am, you want your car to begin charging at 2:00am.
Step 5: Set your car's scheduled charging start time to match. Most EVs support this via their smartphone app. Enter the start time you've identified, set a departure time to ensure the charge completes before you need the car, and you're done.
The whole process, including opening AgileAlert and adjusting your car's schedule, typically takes 45-60 seconds once you're familiar with it.
Setting departure time on your EV: car-side scheduling
Every major EV on the UK market supports some form of scheduled charging. The interface varies by manufacturer, but the principle is the same: you tell the car when you need it ready, and it manages the charge accordingly.
Tesla (Model 3, Model Y, Model S, Model X): Open the Tesla app on your phone, tap your vehicle, go to Charging, then Schedule. You can set both a departure time (the car finishes charging by this time) and a start time. Tesla's off-peak scheduling can also be configured to align with your utility's cheap rate periods.
Nissan Leaf: Use the timer button on the dashboard to set charging start and end times. Two timers can be saved for different daily schedules. The Nissan Connect app also allows remote scheduling.
VW ID.4 (and ID.3, ID.5): Navigate to the charging menu in the car's infotainment system, or use the Volkswagen ID app. Set a ready-by time and the car will calculate when to begin charging. You can also set a preferred departure time window.
Kia EV6 (and EV9, Niro EV): Use the Kia Connect smartphone app to set a charge schedule with departure time. The car can also be configured directly via the in-car menu under Vehicle Settings and Charging.
Hyundai IONIQ 5 (and IONIQ 6): Use the Bluelink app or the in-car charging schedule menu. Set departure time and preferred charging time windows.
BMW iX3 (and i4, iX): Use the My BMW app to set a departure timer. The car will charge in the cheapest window before that time if it's on a tariff that supports this, or simply start at your manually set time.
The principle across all these cars is similar. Set your departure time first. This gives the car a deadline. Then set a start time that corresponds to the cheapest Agile window you've identified. The car will charge within those bounds.
Does it matter which hour within the overnight window you target?
Yes, and more than most drivers expect. The price difference between the cheapest and second-cheapest overnight slot can easily be 2-4p/kWh. On a 60kWh battery, a 2p/kWh difference equals £1.20 per charge. On 100 charges per year, that's £120 in savings from targeting the single cheapest slot rather than just any overnight slot.
On nights with wider price variation, the stakes are higher. If prices range from 2p to 8p within the overnight window, the difference between charging at the cheapest versus the most expensive overnight slot is 6p/kWh, or £3.60 on a 60kWh charge. That's £360 per year if you charge that frequently.
The 60 seconds it takes to check AgileAlert and adjust your scheduled start time has an effective hourly rate of hundreds of pounds. Very few two-minute tasks in personal finance return this kind of value.
How overnight Agile rates compare to the price cap unit rate
The July 2026 Ofgem price cap sets the standard electricity unit rate at 26.11p/kWh. That's the rate you pay on a standard variable tariff. Most EV owners on non-Agile tariffs pay something close to this for all their electricity, including overnight charging.
The typical overnight Agile rate sits between 3p and 6p/kWh. On a good night, 2p or lower. On an exceptional plunge event, prices go negative.
The saving per kWh: 20-23p on average versus the price cap rate. On a 60kWh charge, that's a saving of £12-14 per charge compared to charging at the price cap rate. Against peak Agile prices (which can reach 38p/kWh or higher between 5pm and 8pm), the overnight saving is even larger. Charging that same 60kWh car at a 38p peak rate costs £22.80. At 4p overnight, it costs £2.40. The difference is £20.40 on a single charge.
This is why EV owners on Agile treat peak hours as a no-go zone for charging. The combination of cheap overnight rates and deliberately avoided peak rates creates the full Agile saving. Miss one side of this, and you lose much of the benefit.