How to save £1-2 a day on energy bills with Home Assistant (UK)

Energy prices in the UK have been high and volatile for years now. The headlines come and go, the Ofgem price cap moves up and down, and most of us have settled into a quiet resignation that heating the house and running the washing machine just costs more than it used to. The usual advice — unplug your chargers, boil less water, wear a jumper — is tired, vague, and won't move your bill in any meaningful way.

This guide is about something more specific. If you have Home Assistant running, or you're thinking about it, there are three things you can automate that together save a typical UK household — especially one with solar, an EV, a heat pump or a home battery — somewhere between £1 and £2 a day. That's £365 to £730 a year, from arithmetic, not wishful thinking. No insulation works, no behaviour change, no hair shirts. Under the April 2026 Ofgem price cap the typical UK dual-fuel household pays around £1,641 a year for energy, and higher-use households pay considerably more; a reduction of 15-30% is genuinely within reach once the right automations are in place. If you want a one-line version: this is how to use Home Assistant to save money on energy bills in the UK, with specific numbers and three practical automations.

How Home Assistant saves money on your energy bill

Home Assistant is a small computer that sits on your home network and talks to things. For energy, it reads your smart meter (either directly through the Octopus Energy integration or via a Hildebrand Glow IHD that streams half-hourly data), it reads your electricity tariff prices if you're on a variable plan, it reads your solar inverter if you have one, and it reads your heat pump, EV charger, hot water tank and major appliances if they're smart.

Then it orchestrates. It tells the dishwasher to start at 2am because that's the cheapest half-hour tonight. It tells the hot water tank to top up while the sun is on the panels. It holds the heat pump back for an hour because electricity is about to get cheaper. It's not magic and it's not AI. It's a handful of rules running on a Raspberry Pi in a cupboard.

The reason it matters is that electricity is no longer a single price. On the right tariff, the same kWh can cost you 5p at 3am and 30p at 6pm. If you can move your big loads from the 30p slot to the 5p slot, the savings are immediate and measurable.

The three levers that actually move the needle

Most of what you'll read about saving energy with smart homes is noise. Turning off standby gadgets saves pennies. Motion-activated lights are nice but LEDs already sip electricity. The real money is in three specific levers, and Home Assistant is good at all three.

Lever 1: Time-shift your big loads to cheap electricity

This is the biggest and easiest win, and it's available to anyone regardless of whether you own solar panels, an EV or a heat pump.

Smart tariffs in the UK have quietly become very good. Octopus Agile gives you a different electricity price every half hour, published the afternoon before, often cheapest overnight and sometimes mid-afternoon when wind and solar are strong. Octopus Go and Octopus Intelligent Go give you a cheap overnight window — typically around 7-8p per kWh in 2026 — compared to a standard cap flat rate of around 25p and peak time-of-use rates closer to 28-30p. Octopus Cosy is designed for heat-pump homes. (Octopus Flux, the solar-plus-battery export tariff, closed to new customers in March 2026, although existing Flux customers still use it.) On a standard flat tariff, every kWh costs roughly the same. On a smart tariff, that gap between peak and off-peak is where the savings live.

Home Assistant lets you wait for the cheap periods automatically. You tell the automation "start the dishwasher in the next cheapest three-hour window before 7am" and it does exactly that. The same logic works for the washing machine, the tumble dryer, the dehumidifier, pond and pool pumps, and anything else that runs for a chunk of time and doesn't care when. Some appliances support delayed start from their own app; Home Assistant just picks a better time than you would.

A household running a dishwasher, washing machine and an occasional tumble dryer or immersion top-up can typically shift 3 to 5 kWh a day this way. At the difference between roughly 7-8p off-peak and 25-28p on a standard or time-of-use tariff, that's somewhere in the region of £0.50 to £1.00 a day, every day, once the automations are set up. You're not using less electricity. You're paying less for the electricity you already use.

If you're already on Agile or thinking about switching, there's a deeper guide on Octopus Agile with Home Assistant that walks through the integration and the specific automations.

Lever 2: Actually use the solar electricity you generate

Over 1.6 million UK homes now have solar panels on the roof. If that includes you, there's a quiet trap in how the economics work, and Home Assistant is the tool that springs it.

Every kWh of solar you use inside the house is worth roughly 25p at the April 2026 price cap, because it's a kWh you didn't have to buy from the grid — and more on a peak time-of-use slot. Every kWh you export back to the grid under the Smart Export Guarantee is worth somewhere between about 3p and 12p depending on your supplier and tariff (Octopus Outgoing Fixed dropped from 15p to 12p in March 2026, and the lowest SEG rates sit in the low single digits). So a unit of solar electricity is worth two to six times as much if you use it yourself than if you send it back. The difference is significant and it adds up all year.

The problem is that solar peaks in the middle of the day, when nobody's home and nothing's running. The default outcome is that most of your solar gets exported for pennies while you come home at 6pm and buy grid electricity at peak rates to cook dinner and run the dishwasher. Home Assistant fixes this by watching your inverter in real time and diverting excess solar to things that can store or absorb it. The hot water tank is the classic target — a MyEnergi Eddi, a Marlec Solar iBoost+ or a Shelly-controlled immersion relay can dump surplus solar into hot water and effectively give you a free tank of hot water on most summer days. Home batteries can charge. EV charging can ramp up and down to match. Heat pumps can pre-heat the house. Dishwashers and washing machines can be scheduled for solar peaks instead of overnight cheap slots when production is strong.

A 4 kWp solar array on a typical UK roof produces somewhere in the range of 3,200 to 4,200 kWh a year. Shifting even 1,000 kWh of that from export back to self-consumption is worth roughly £90 to £220 a year in avoided grid imports, depending on your export rate and your import tariff. For households with larger arrays or batteries, the numbers get bigger.

The full walkthrough lives in the solar with Home Assistant guide, including how to read your inverter and set up diversion automations.

Lever 3: Smart heating and hot water

Heating is where most UK households spend the most, and it's where the automation story is most nuanced.

Heat pumps are genuinely brilliant when they're run well. In real UK installations they typically deliver two to three times more heat per unit of energy than a gas boiler (Energy Saving Trust field-trial data published on gov.uk records SPFH4 averages of 2.45 for air-source and 2.82 for ground-source heat pumps; modern installs in well-insulated homes routinely beat 3.0), but that efficiency only turns into savings if the electricity they drink is cheap. Running a heat pump on a standard flat tariff around 25p per kWh is workable. Running it on Octopus Cosy or Agile, with Home Assistant scheduling the hot water cycle and the main heating boost during cheap windows and solar peaks, is where the economics actually beat gas in most homes. If you have a heat pump and you're not scheduling it around tariff prices, you're leaving real money on the table every single day.

Hot water is the simpler version of the same idea. Whether you're on a heat pump, an immersion heater or a gas combi with a stored cylinder, the rule is the same: heat water when electricity is cheap or when the sun is shining, not on demand at peak rates. Scheduling an immersion to top up overnight or at midday rather than whenever someone fancies a bath typically saves somewhere in the range of £0.30 to £0.80 a day, depending on how much hot water your household gets through.

Then there's zonal heating. Smart thermostatic radiator valves from Aqara, Tado or Drayton Wiser let Home Assistant heat only the rooms you're actually using, based on presence, time of day and room-by-room schedules. The bedroom doesn't need to be warm at 9am. The home office doesn't need to be warm at 9pm. The spare room doesn't need to be warm at all unless someone's staying. Households that move from a single hallway thermostat to proper zonal control typically see heating costs fall by 10 to 20%, and that's before you start layering in tariff-aware scheduling on top.

What you actually need to get started

The ingredient list is shorter than you'd think. You need a working Home Assistant install — a Raspberry Pi 5 with an SSD is the reliable choice (a Pi 4 still works if you already own one), booted from HA OS. You need a smart meter, or a Hildebrand Glow IHD plugged in next to your meter if you want faster half-hourly data than the default feed. You need the Octopus Energy integration from HACS if you're on a variable Octopus tariff — it pulls in your live prices, your consumption and your account details automatically. You need whatever smart plugs, relays or native integrations let Home Assistant actually control the appliances you want to time-shift. And you need an hour or two of configuration per automation to get the logic right for your household.

None of this is hard in the sense that any single step is beyond a careful reader. It is hard in the sense that there are a lot of steps, they all have to work together, and they need ongoing maintenance. Integrations occasionally break when Octopus changes an API. Home Assistant releases a new version every month and sometimes an update needs attention. The Cloudflare tunnel you set up for remote access needs to stay healthy. Backups need to actually run. This is the part of the story that the enthusiast forums quietly gloss over.

Who this works for, and who it doesn't

It's worth being honest about where the arithmetic in this guide applies and where it doesn't.

It works well for anyone on a variable tariff like Octopus Agile, Go, Intelligent, Flux or Cosy. It works well for anyone with solar panels, especially paired with a hot water tank or a home battery. It works well for anyone with a heat pump, where the combination of a variable tariff and smart scheduling can be the difference between a cheap bill and an expensive one. It works well for anyone with an EV, where a single automation shifting charging into the cheap overnight window pays for the entire Home Assistant setup several times over in a year.

It works less well — though still not nothing — for households on a fixed flat tariff with no solar, no EV, no heat pump and no home battery. You can still get some value from scheduling and zonal heating, but the headline numbers in this guide assume you're using at least one of the tools above. If you're on a fixed tariff, the single biggest thing you can do is look at whether a smart tariff makes sense for your usage pattern; Home Assistant can help you work that out from your own consumption data before you switch.

It doesn't work for people who genuinely don't want to learn how to read a line chart or think about when their appliances run. That's fine — there's no shame in it — but those households are probably better served by a simpler product than Home Assistant, or by paying somebody else to run it for them.

The honest closing note

The arithmetic in this guide is real. £1 to £2 a day is achievable for a typical UK household that puts the three levers in place, and it's considerably more than that for homes with solar, batteries or a heat pump on the right tariff. None of it requires new insulation, new appliances or a change in how anyone in the household actually lives. It does require Home Assistant to be set up properly once and then kept running, and the second half of that sentence is where most self-built systems quietly fall over six months in.

If you want to do it yourself, the deeper guides on Octopus Agile, solar, heat pumps and EV charging are the next places to go. If you'd rather somebody else handled the setup, the updates, the backups and the occasional 10pm phone call when an integration breaks, you can see how habbb works — it's a managed Home Assistant service for UK homeowners, designed for people who want the savings without the maintenance. Either way, the numbers are sitting there waiting to be collected.