Figure 1
Third-party monitoring apparently incorrectly installed illustrated by return temperature exceeding flow temperature.
Figure 2
Daily heat pump electricity consumption for one Energy Demand Observatory and Laboratory (EDOL) participant during a period in summer.
Table 1
Summary of the discrepancies between third-party and onboard monitored data for six of the sites in Monitoring and Comparing of Air Source Heat Pumps (MacAirH) and Energy Demand Observatory and Laboratory (EDOL).a
| SITE | MacAirH1 | MacAirH2 | MacAirH3 | MacAirH4 | EDOL1 | EDOL2 | |
|---|---|---|---|---|---|---|---|
| Electricity consumption | Third party (kWh) | 125 | 324 | 70.4 | 123 | 1,803 | 275 |
| Onboard (kWh) | 134 | 324 | 70.5 | 106 | 1,894 | 272 | |
| Discrepancy (%) | –7% | 0% | 0% | 14% | –5% | 1% | |
| Heat output | Third party (kWh) | 442 | 754 | 274 | 383.4 | 7,676 | 1,259 |
| Onboard (kWh) | 313 | 713 | 301 | 413 | 6,070 | 1,226 | |
| Discrepancy (%) | 29% | 5% | –10% | –8% | 21% | 3% | |
| Performance ratio | Third party | 3.55 | 2.30 | 3.89 | 3.10 | 4.26 | 4.58 |
| Onboard | 2.34 | 2.20 | 4.28 | 3.90 | 3.21 | 4.51 | |
| Discrepancy (%) | 34% | 4% | –10% | –26% | 25% | 2% | |
| Start date | 1 October 2023 | 1 December 2024 | 2 October 2023 | 1 December 2024 | 1 August 2022 | 1 February 2024 | |
| End date | 31 October 2023 | 31 December 2024 | 20 October 2023 | 31 December 2024 | 30 April 2023 | 29 February 2024 | |
| End-uses included | Space heating only | Space heating only | Space heating only | Space heating only | Space heating and DHW | Space heating and DHW |
[i] Note: aDiscrepancy is defined as 100 × (third party – onboard)/third party).
DHW = domestic hot water.
Figure 3
Example from one home in the Energy Demand Observatory and Laboratory (EDOL) project. Flow temperature recorded by onboard monitoring deviates from third-party reading when flow temperature is raised.
Table 2
Costs of various onboard and third-party monitoring options retrofitted onto a single existing heat pump installation.
| ONBOARD MONITORING | THIRD-PARTY MONITORING | ||||||
|---|---|---|---|---|---|---|---|
| OB1 | OB2 | TP1 | TP2 | TP3 | TP4 | TP5 | |
| Installation cost (€) | €600 | €600 | €1,200 | €1,200 | €150 | €1,200 | €150 |
| Hardware (€) | €360 | €305 | €1,360 | €1,270 | €877 | €1,540 | €370 |
| Annual fees (€) | €120 | €120 | €120 | €140 | €150 | €170 | €120 |
| Total cost (for one year) (€) | €1,080 | €1,025 | €2,680 | €2,610 | €1,177 | €2,910 | €640 |
| Number of SEPEMO boundaries | 2 | 1 | 4 | 4 | 4 | 4 | 1 |
| Cost per SEPEMO boundary (one year) (€) | €540 | €1,025 | €670 | €653 | €294 | €728 | €640 |
| Total cost (for five years) (€) | €1,560 | €1,505 | €3,160 | €3,170 | €1,777 | €3,590 | €1,120 |
[i] Note: All cost data were collected between Q4 2022 and Q1 2024.
SEPEMO = seasonal performance factor and monitoring.
Table 3
Key features of onboard monitoring of six common heat pump brands (labelled 1-6) and third-party monitoring.
| THEME | QUESTION | ONBOARD MONITORING FROM HEAT PUMP BRAND | THIRD-PARTY MONITORING | |||||
|---|---|---|---|---|---|---|---|---|
| 1 | 2 | 3 | 4 | 5 | 6 | |||
| Measurement | How is electricity measured/estimated? | Inferred | Metered | Inferred | Inferred | Unclear | Metered | Metered |
| How is heat measured/estimated? | Inferred from the calculated flow rate and measured temperatures | Using measured flow rate and measured temperatures, but not as a MID-approved heat meter | Using measured flow rate and measured temperatures, but not as a MID-approved heat meter | Using measured flow rate and measured temperatures, but not as a MID-approved heat meter | Using measured flow rate and measured temperatures, but not as a MID-approved heat meter | Using measured flow rate and measured temperatures, but not as a MID-approved heat meter | Using measured flow and measured temperatures. Meets EN-1434 standard for a heat meter (CEN 2025) | |
| Is uncertainty on reported electricity stated in any documentation? | No | Yes, uses a MID-approved meter | No | No | No | No | Yes, uses a MID-approved meter | |
| Is uncertainty on reported heat stated in any documentation? | No | No | No | No | No | No | Yes | |
| To which SEPEMO system boundary does the reported SPF correspond? | Unclear | Unclear | Unclear | Unclear | Unclear | Unclear | As many as desired depending on the extent of electricity meters used | |
| Customer access to data | Does the system report heat pump performance (e.g. SPF) to the customer? | Almost: reports heat and electricity | Yes | Yes | Yes | Yes | Almost: reports heat and electricity | Some provide SPF, others heat and electricity |
| Are electricity data available to the customer? | Yes, monthly, via an app or in-home display | Yes, hourly, via an app or in-home display | Yes, daily, via an app or in-home display | Yes, daily, via an app or in-home display | Yes, daily, via an app or in-home display | Yes, daily, via an app or in-home display | Yes | |
| Are heat data available to the customer? | Yes, monthly, via an app or in-home display | Yes, hourly, via an app | Yes, daily, via an app or in-home display | Yes, daily, via an app or in-home display | Yes, daily, via an app or in-home display | Yes, daily, via an app or in-home display | Yes | |
| What is the cost of data access for the customer? | Free internet gateway. Annual fee for the app at the time of research; now free at the time of writing | One-off cost for the internet gateway, about €140 | Newer models come with an internet connection as standard and a free app | Newer models come with an internet connection as standard and a free app | Newer models come with an internet connection as standard | One-off cost for the internet gateway, about €170 | Most systems at least €1000 for hardware and installation. Annual fees around €10/year assuming the home already has wi-fi | |
| Researcher access to data | Are diagnostic parameters such as heat pump flow and return temperatures available? | Yes, if extra hardware is installed | Yes, if extra hardware is installed | Yes, if extra hardware is installed | Yes, if extra hardware is installed | Yes, if extra hardware is installed | Yes, if extra hardware is installed | Yes |
| Are data time-stamped by heat pump mode? | Yes | Yes | Yes, although the research team could not find Legionella cycle or defrost modes | Yes | Yes | Yes | Difficult, requires a sensing three-way valve or use of flow temperature values, which is not fully reliable | |
[i] Note: MID = Measurement Instruments Directive; SPF = seasonal performance factor.
Table 4
Current costs (€, 2025) of elements of monitoring equipment for one heat pump, not bought wholesale.
| ITEM | CURRENT RETAIL COST OF ONE ITEM (€) |
|---|---|
| One flow meter and one matched pair of temperature sensors | €115a |
| One to three Measurement Instruments Directive (MID)-approved electricity meters: one for heat pump input, others for back-up heating electrical input | €40 eachb |
| One unmatched pair of temperature sensors for indoor and outdoor temperatures | No extra cost: all heat pumps already have these for their own control logic |
| Annual server cost | €5 (estimated) |
| Total cost for 10 years of monitoring | €205 |
[i] Note: It is assumed that the heat pump is already internet connected.
aOne set of a flow meter and paired temperature sensors can be bought for £100/€115, e.g. Vaillant 0020045923 Sensor, Vortex, Dn15 and Matched Pair PT 500 Temperature sensors | Insertion RTD Probes and Pockets. Procured at scale, the costs per unit would be expected to substantially reduce.
bOne can be bought for about £33/€40, e.g. Emlite ECA2 MID Single Phase 20-100A Direct Connected Meter—Meter Market.