Energy House Labs testing supports findings that Homely can save £444* / year with Time-of-Use (ToU) tariff

Following an extensive period of testing at the Energy House Labs facility at Salford University, Greater Manchester, UK, we are delighted to share the results of our findings. Homely can reduce heating bills by £444* / year for UK heat pump customers with a time of use (ToU) energy tariff.1

Homely has been maximising savings for heat pump users with ToU tariffs for some time, but how does it save so much? It’s because Homely goes beyond simply blasting your heat pump during cheap periods. Instead, it factors in:

  • Heat pump performance: Efficiency (or its Coefficient of Performance (CoP)) is considered across various outdoor and flow temperatures.
  • Weather forecasts: Accurately predicting heating needs based on anticipated temperatures.
  • Electricity prices: Dynamically adjusting operation based on prices that are either specified by the user or API-fetched (e.g. Octopus Agile, Nordpool).

This is while always prioritising customer comfort as minimum and maximum comfort temperature ranges are user-defined.

Octopus Tariffs: Flexible fixed rate vs Cosy ToU

The CoP vs cost vs comfort tradeoff: Why blasting isn’t best

A common misconception is to simply run the heat pump at maximum output during cheap periods. Homely avoids this for two key reasons:

  1. CoP degradation: Running a heat pump at excessively high flow temperatures reduces its CoP, negating cost savings.
  2. Overheating penalty: Excessive temperature increases before the more expensive periods create a larger thermal difference between inside and outside temperature, leading to unnecessary heat losses and customer discomfort.

Homely finds the optimal “sweet spot” between pre-heating for cheap periods and minimising CoP losses to ensure maximum cost savings while maintaining comfort.

ToU Savings: Beyond just switching tariffs

Our research reveals that simply switching to a ToU tariff without adjusting heating behavior often leads to higher heating bills due to the alignment of the typical heating periods (in our case SAP heating profile2) to the more expensive periods of the day.

Homely optimises heating for the customer’s specific tariff structure and temperature requirements.

Test environment:
  • Where: Energy House facility at Salford University
  • Base cases:
    • Base Case 1 (Weather Compensation Base Case): Controller of the heat pump (OEM) set up with a weather compensation as per the MCS Best Practice Guide
    • Base Case 2 (Fixed Flow Base Case): Controller of the heat pump (OEM) set up without weather compensation at design flow temperature
    • Comfort Setpoints: 21°C (7:00-9:00 AM & 4:00-11:00 PM)3
    • Setback: 19°C (all other times)
  • Electricity Tariff: “Cosy” from Octopus Energy – The smart electricity tariff designed to keep heat pump homes toasty.
    • Day Rate: 26.52 p/kWh
    • Cosy Rate (Cheap): 15.91 p/kWh (4:00-7:00 AM & 1:00-4:00 PM)
    • Peak Rate (Expensive): 42.43 p/kWh
  • Measurement: Power consumption Seasonal Performance Factor (SPF[H2]) for heating only

Our Energy House testing ran for over 3 months testing different heating scenarios in both UK winter and shoulder season conditions. Homely and base case scenarios were tested using different tariffs and different set ups of the system, including heat pump only and then including battery and PV. We will be sharing more on these results in future updates however today we are pleased to announce our results regarding the ToU tariff tests!


Homely goes beyond basic ToU integration for heat pumps. Our intelligent system optimises comfort and cost savings by considering weather forecasts, tariff structures, and heat pump performance. By joining Homely, end-customers get the best of both worlds: a warm and comfortable home while maximising their ToU tariff benefits to significantly lower their overall cost of heating.

Homely is compatible with all ToU tariffs available on the market, including those which are primarily targeted at overnight cheap periods for EV charging.

Keep up to date on the latest news from Homely, including future results for PV and Battery optimisation by following our page on Linkedin or signing up to our newsletter.

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1 – Annualised Savings Methodology:

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