Detached property, hosted by John

We have done some minor upgrades to our house when we were on gas central heating to improve its thermal efficiency. Sealing up draughts, blocking the chimney, new window seals all round, extra loft insulation. All small things but coupled together made a difference. Before getting the heat pump we ran our 22 year old gas boiler at its lowest setting for 18 months to see if we could operate with low flow temperatures - it did but struggled as it was non-condensing with very basic heating controls. Once the heat loss survey was completed we had a 8.4.kW heat loss at -2.4ºC. To get the 40ºC flow temp we wanted we had to upgrade all our 16 radiators. We could have opted for 45ºC flow temp which would have reduced the need to replace as many radiators. I figured in the long run it was worth spending a little more up front for the longer term 20 year gains of cheaper running costs. 

Heat pump & Hot Water Store
Vaillant 7kW aroTHERM+

Vaillant uniSTOR 200ltr tank

Heat pump controls
Design flow temperature: 40°C
Outside design temperature: -2.4°C
Typical flow temperature: 29°C @ 6°C
Weather compensation curve: 0.4
Freeze protection: Anti-freeze valves
Number of zones: 1
Space heat control type: Pure weather compensation, no room influence
DHW control type: Daily scheduled heat up of tank
DHW target temperature: 45°C
Legionella frequency: Disabled

Performance from 20 Sep 2023 to 21 April 2024:

Total Electricity input: 2,725 kWh
Total Heat output: 11,745 kWh
SCOP: 4.31

Notes
Pipework throughout is 10mm micro-bore pipework mainly copper but some plastic in the newer extension. 

Solar PV
4.0kW solar array, installed Sept 2011, 16 x 250w Sanyo HIT-H250E01 panels

2.34kW solar array, installed Oct 2019, 6 x SunPower Maxeon 3 390w panels

Home Battery
Tesla Powerwall 2 x2 (Gateway 2), 1st installed Dec 2018, 2nd added May 2024

Tariff & Generation
Electricity tariff: Octopus Intelligent
Tariff type: On peak & Off peak
Average unit rate paid for all electricity: 7p/kWh
Annual solar PV generation: 6200 kWh
Solar PV self consumption: 100 %
Solar PV divert to hot water immersion
Battery storage capacity: 27kWh
Kaifa MA120 SMETS2 smart meter

Other controls
myenergi eddi, installed July 2019
myenergi zappi v1, installed Dec 2018
myenergi harvi x 2
myenergi hub
myenergi iOS app
Home Assistant for monitoring and automations

BEVs
Tesla Model 3 AWD Performance, delivered 28th Sept 2019
Hyundia Kona SE 64kW, delivered 1st July 2019 - sold Dec 2021
Renault Zoe 22kW, delivered 5th Jan 2022

Based in Rushden, East Midlands, UK