Smart Meter + Heat Pump Optimization UK 2026
Pair a SMETS2 smart meter with a heat pump and a half-hourly tariff and you bank £180-£420 every year. Here's how to set it up — Cosy windows, MELCloud schedules, sensoApp automation, and what most installers don't tell you.
Why a smart meter is non-negotiable for heat pump owners
Standard non-smart meters are stuck on the Ofgem-capped flat rate (~26p/kWh in 2026). With a SMETS2 smart meter, you can switch to a half-hourly tariff that charges different rates throughout the day. For a heat pump household using 8,000-12,000 kWh/year, the difference is £180-£420/year.
SMETS1 meters work but may not support all tariffs — most suppliers have upgraded the firmware so they behave like SMETS2 now. If you're unsure, your supplier app will tell you.
The Octopus Cosy windows in detail
| Window | Time (winter) | Approx rate | What to do |
|---|---|---|---|
| Cheap morning | 04:00-07:00 | ~12.5p/kWh | Pre-heat fabric, full DHW cycle |
| Daytime cheap | 13:00-16:00 | ~12.5p/kWh | Top-up heating, DHW boost if needed |
| Standard | 07:00-13:00, 16:00-22:00 | ~24p/kWh | Normal scheduled heating |
| Peak | 16:00-19:00 | ~36p/kWh | Throttle to minimum or off |
| Evening cheap | 22:00-00:00 | ~12.5p/kWh | Pre-heat for night, recharge cylinder |
Octopus rates shift quarterly. Always check current rates in the Octopus app before changing schedules.
The three things to automate
1. Domestic Hot Water (DHW) scheduling
Heat your cylinder during cheap windows only. A 250L unvented cylinder typically takes 90-180 minutes to recover from cold. Set the DHW schedule:
- 04:00 - cycle to full 50°C (sterilisation cycle weekly at 60°C)
- 13:00 - top-up if used heavily during morning
- 22:00 - recharge for evening usage
- NO DHW heating during 16:00-19:00 peak
2. Space heating "pre-heat"
Set the home thermostat 1°C higher during cheap windows, then drop by 1°C during peak. The thermal mass of the building holds heat through the 16:00-19:00 expensive window without comfort loss.
- 04:00-07:00: setpoint 20°C (pre-heat)
- 07:00-13:00: setpoint 19°C (steady)
- 13:00-16:00: setpoint 20°C (top-up)
- 16:00-19:00: setpoint 18°C (coast on thermal mass)
- 19:00-22:00: setpoint 19°C (modest recovery)
- 22:00-00:00: setpoint 19°C (gentle recharge)
3. Defrost cycle timing
Some controllers let you schedule defrost cycles. Push them into cheap windows when possible — defrost takes ~5 minutes and consumes 0.3-0.5 kWh extra.
How to set this up by brand
Mitsubishi MELCloud
MELCloud has a "Schedule" tab with 8 daily events per controller. Set 6-8 setpoint changes mapping to the Cosy windows. The Mitsubishi Ecodan also has an "Energy Monitor" reporting kWh usage by hour — invaluable for tuning.
Vaillant sensoApp / sensoComfort
sensoComfort supports 7 schedule points per day plus weather compensation. Use the "ECO" mode for peak hours and "COMFORT" for cheap windows. The sensoApp updates schedule remotely.
Daikin Onecta / Madoka
Daikin's Onecta app allows custom schedules with 6 points per day. The Madoka controller has a "Setback" function ideal for the 16:00-19:00 peak.
Grant Aerona 290
Grant's Mi-Control supports 4-step daily scheduling and weather compensation. Less granular than Mitsubishi but sufficient for Cosy windows.
Samsung EHS / LG Therma V
SmartThings (Samsung) and ThinQ (LG) both support scheduling. Less mature than MELCloud or sensoApp but improving — both added Octopus Cosy tariff integration in 2024-25.
Real saving examples (2026 prices)
| Home | Annual kWh | Std cap cost | Cosy optimised cost | Saving |
|---|---|---|---|---|
| 2-bed terrace | 5,500 | £1,450 | £1,160 | £290/yr |
| 3-bed semi | 8,000 | £2,110 | £1,690 | £420/yr |
| 4-bed detached | 11,500 | £3,030 | £2,510 | £520/yr |
| 1-bed flat | 3,500 | £925 | £745 | £180/yr |
Assumes 60% of heat load shifted to cheap windows. Real-world results vary 70-130% of these figures based on home thermal mass, scheduling discipline, and Cosy window utilisation.
Common mistakes to avoid
- Running the heat pump full-blast during peak. The 16:00-19:00 window is 3x the cheap rate. Coast on thermal mass instead.
- Pre-heating too aggressively. Setting +3°C during cheap windows causes overheating and waste. +1°C is optimal.
- Forgetting the DHW Legionella cycle. Once a week run the cylinder to 60°C. Schedule this in a cheap window.
- Manual override panic. Resist the urge to crank up heat at 5pm when chilly — Cosy will punish you. Trust the schedule.
- Not updating schedules seasonally. Summer (less heat demand), spring (transitional), winter (full optimisation) each warrant different schedules.
Smart meter installation — what to know
Smart meter installs are free from your supplier under the UK rollout. Booking via Octopus, EDF, British Gas etc. takes 4-12 weeks depending on demand. The install itself is 1-2 hours and includes both gas and electric meters.
Practical tips:
- Pick a supplier that has working SMETS2 firmware for half-hourly tariffs (Octopus is gold standard)
- Confirm the meter has signal — rural West Wales, parts of Scotland still have coverage gaps
- Keep the In-Home Display if offered (not essential but useful for spotting issues)
- After install, wait 24-48 hours before switching tariffs — the meter needs to "register" with the supplier
Beyond Cosy — Intelligent Octopus and Agile
If you're on a heat pump and want maximum savings, two other tariffs are worth knowing:
- Intelligent Octopus Go — designed for EVs but accepts heat pumps. 6 hours of guaranteed 7p/kWh overnight. Excellent if you have predictable heating patterns.
- Octopus Agile — half-hourly rates that change every 30 minutes based on wholesale market prices. Can save more but requires active management or smart home automation (Home Assistant, IFTTT).
For most heat pump owners, Cosy is the sweet spot — significant savings, simple to manage, predictable windows.
Detail: Octopus Cosy vs Standard Tariff