Octopus Agile Home Assistant Automation: A UK Guide

If you have a smart meter and a heavy electricity habit, Octopus Agile Home Assistant automation is one of the quickest wins in UK home tech. Instead of paying one flat rate every hour, your home decides when the big loads run. Hot water, laundry and car charging shift into the cheapest half-hour slots of the next day. For a typical electrified UK household, that shift is worth several hundred pounds a year.

This guide walks through the whole build. You will connect Home Assistant to the Octopus Energy API, pull tomorrow’s half-hourly rates, and trigger real appliances. We also compare the numbers against a standard variable tariff at 2026 Ofgem price cap levels. That way you can judge whether the effort is worth it for your home.

How Octopus Agile Home Assistant Automation Actually Works

Octopus Agile links your unit rate directly to wholesale electricity prices. The rate changes every 30 minutes, and next-day prices are normally published in the late afternoon. Overnight slots often drop to a few pence per kWh. Winter evening peaks can push well above 40p.

A per-unit cap protects you from the worst wholesale spikes. Even so, Agile without automation is a gamble. Households that leave everything on fixed timers frequently pay more than they would on a standard tariff. Flexibility is the entire point of the product, and Home Assistant supplies it automatically.

Agile rewards homes that can move load. It punishes homes that cannot. Automation is what turns the tariff from a lottery into a discount.

Technically, the flow is simple. Home Assistant polls the Octopus Energy API every 30 minutes. It reads the current rate, the next rate and the full day-ahead price list. Your automations then compare those figures against a threshold and switch a relay, plug or charger.

Agile vs the Ofgem Price Cap: The 2026 Numbers

Context matters before you switch. The Ofgem price cap for October to December 2026 puts a typical dual-fuel household at roughly £1,790 a year. Electricity sits at about 25.9p per kWh, with a standing charge near 57p a day. Those figures vary by region and payment method, so always check the current cap.

Standard variable tariff (2026 cap): around 25.9p per kWh, flat, all day
Agile without automation: often 27p to 30p per kWh effective, because you use power at peak
Agile with automation: typically 14p to 16p per kWh effective across a year
Agile standing charge: roughly 50p a day, region dependent
Cheapest slots: commonly 5p to 12p per kWh overnight or on windy weekend afternoons

In other words, the tariff itself is neutral. The automation is what creates the saving. You can read the official methodology on the Ofgem price cap pages if you want the detail behind those unit rates.

What You Need Before You Start

Hardware checklist

A SMETS2 smart meter sending half-hourly readings to Octopus (check this in the app first)
A Home Assistant hub: Home Assistant Green at about £99, a Raspberry Pi 5, or a small mini PC
A 16A smart relay plus contactor for the immersion heater, roughly £40 to £90 fitted
A 13A smart plug with power monitoring for the tumble dryer, £15 to £25
An EV charger with a local API: myenergi Zappi, Ohme Home Pro, Wallbox Pulsar Plus or Hypervolt

Software checklist

HACS, the Home Assistant Community Store
The Octopus Energy integration, which exposes rate sensors and day-ahead events
Your Octopus API key and account number, generated from the developer dashboard
Optional: Node-RED, or a community blueprint that finds the cheapest consecutive block of slots

Connecting Home Assistant to the Octopus Energy API

The setup takes about 20 minutes. Work through it in this order.

Log into your Octopus account and generate a personal API key.
Install HACS on your Home Assistant instance, then add the Octopus Energy integration.
Enter your API key, account number and MPAN when prompted.
Select the Agile tariff product code for your region. These rotate, so pick the one your account shows.
Confirm the sensors appear: current rate, next rate, and the day-ahead rate list.
Rename the entities to something short, such as sensor.agile_current and sensor.agile_next.

Once the sensors are live, every automation becomes a comparison. If the next rate is below your threshold, do the thing. If it is above, wait. In practice the action is a single service call such as switch.turn_on on switch.immersion_heater, guarded by a numeric condition on the rate sensor.

Automation One: Pre-Heating the Hot Water Cylinder

An immersion heater draws about 3kW. Two hours of heating therefore uses roughly 6 kWh. At the 2026 cap rate of 25.9p that costs £1.55. In a cheap Agile block at 8p it costs £0.48. A family that reheats the cylinder daily saves around £1 a day, or roughly £260 a year.

The automation should run once, late morning, when the day-ahead prices are known. It scans the rate list, finds the cheapest two-hour window, and schedules the relay. Add a maximum price guard of 20p per kWh. If no slot qualifies, the relay falls back to a standard 01:00 to 05:00 window.

Safety matters here. Never bypass the cylinder thermostat, and keep the immersion’s own cut-out in circuit. Furthermore, keep a weekly cycle that heats the cylinder to at least 60°C to control legionella bacteria. Cheapest-slot heating must not override that.

Automation Two: Deferring the Tumble Dryer

A heat-pump dryer uses around 1.5 kWh per cycle, while a vented model can use 2.5 kWh or more. Four cycles a week on a vented machine equals roughly 520 kWh a year. Shifting those cycles from 25.9p to 8p saves about £90 annually.

Home Assistant should not simply start the dryer at 03:00. Damp laundry sitting overnight is a mould risk, and nobody wants to unload at dawn. Instead, use the smart plug to notify you when a cheap window is about to open. A dashboard card and a phone alert work well. You load the drum, tap once, and the plug energises at the right moment.

Use power monitoring to detect when the cycle ends, then send a second notification. For example, a drop below 10W for five minutes means the load is finished. That single automation removes most of the friction from load shifting.

Automation Three: Pausing and Resuming EV Charging

Car charging is where the money really sits. A driver covering 7,500 miles a year at 3.5 miles per kWh needs about 2,140 kWh. At the cap rate that is £555. Charged entirely in 9p Agile slots, it drops to roughly £193. That is a saving of over £360 a year from one automation.

The pattern is straightforward. Set a target state of charge and a departure time in the charger’s own app as a backstop. Then let Home Assistant enable and pause charging according to the rate sensor. The Zappi integrates natively, while Ohme and Wallbox both have solid community integrations.

However, do not pause a charge session on a public AC post or a workplace charger. Some networks charge idle fees, and some will not resume cleanly. Keep the automation inside your own driveway.

If you are still choosing hardware, our UK EV charger installation guide covers the models that expose a usable local API. That detail matters far more than raw charging speed for this project.

Wiring, Safety and Smart Meter Requirements

Any new circuit is notifiable under Part P of the Building Regulations in England and Wales, so use a registered electrician.
Immersion circuits are usually 16A and should be switched through a contactor, not a plug-in relay.
Half-hourly readings must be enabled in the Octopus app, otherwise Agile billing falls back to estimates.
Check your home insurance and any tenancy agreement before adding hardwired switching.
If you install a new chargepoint, check the GOV.UK guidance on EV chargepoint grants for current support.

Real Annual Savings: Agile Automation vs Standard Variable

Here is a like-for-like comparison for a three-bedroom home with an EV, an electric immersion and a vented dryer. Figures use November 2026 rates and will vary by region.

Hot water (2,000 kWh shifted): £518 on the cap vs £160 on Agile, saving £358
Laundry (520 kWh shifted): £135 vs £42, saving £93
EV charging (2,140 kWh shifted): £555 vs £193, saving £362
Total annual saving: roughly £810, minus about £99 of hardware if you start from scratch

That is a realistic, not a best-case, figure. Consequently the payback on a Home Assistant Green and a couple of relays is under three months. Add balcony solar panels and the same automations can soak up your own generation first, which improves the return again.

Pitfalls to Avoid

Do not automate without a price ceiling. Winter evening spikes are real and they are expensive.
Do not assume rates arrive on time. Add a fallback schedule in case the API is late.
Do not let a dryer run unattended overnight in a garage without a working heat alarm.
Do not ignore negative prices, which still appear on windy weekend afternoons, but do not build a business case around them.
Do not forget a manual override switch on the dashboard, for guests and for boiler service days.

Finally, remember that Agile suits some homes better than others. If you are out all day and cannot shift anything, a fixed tariff plus a dedicated EV tariff such as Intelligent Go may beat Agile outright. Our full home automation setup guide covers how to layer these automations alongside heating, lighting and solar logic without creating a maintenance headache.

Have you built an Agile automation that survives a British winter? Tell us which template sensor or blueprint earned its place on your dashboard, and which one you quietly deleted after a week.