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Trystan Lea @trystanlea.bsky.social · 08/01/2026

Most of the systems on HeatpumpMonitor run at lower flow temperatures than this and some with only minor radiator upgrades. Heat loss calculations have over-estimated heat loss in pre-2000 buildings in particular in the UK and this has over-inflated expectations of the flow temperatures required.

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Trystan Lea @trystanlea.bsky.social · 08/01/2026

On your question on required flow temperatures. That's an interesting one. It seems that there are a very large number of properties in the UK with sufficient existing radiators to run at flow temperatures of between 45-50C without radiator upgrades. This is what enables HeatGeek's ZeroDisrupt model

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Trystan Lea @trystanlea.bsky.social · 08/01/2026

On HeatpumpMonitor.org we have high performing heat pumps across a wide range of makes and models from budget to premium brands. Some makes and models make it easier to achieve higher performance due to better controls - but even those with poor controls can work well with the right settings.

heatpumpmonitor.org

HeatpumpMonitor.org - Heat Pump Performance Data

An open-source initiative to share and compare heat pump performance data. Join our community of heat pump owners sharing real-world performance data.

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Trystan Lea @trystanlea.bsky.social · 08/01/2026

2/2 This improvement is almost entirely down to better installation, commissioning and operation of these systems. It highlights what the best installers can achieve. The Electrification of Heat trial published last year used the same generation of heat pump technology but only achieved SPF 2.8.

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Trystan Lea @trystanlea.bsky.social · 08/01/2026

Key finding of the paper is not all recent heat pump installations are delivering these efficiencies but that the specific set of heat pump installations that we are monitoring on HeatpumpMonitor.org are achieving much better performance than previous trials. 1/2

heatpumpmonitor.org

HeatpumpMonitor.org - Heat Pump Performance Data

An open-source initiative to share and compare heat pump performance data. Join our community of heat pump owners sharing real-world performance data.

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Trystan Lea @trystanlea.bsky.social · 08/01/2026

Must be something else as well, it's been way colder over the last week than today?

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Jan Rosenow @janrosenow.bsky.social · 05/01/2026

Well-installed heat pumps installed in the UK today achieve on average a 64% higher efficiency than those during the early trials 15 years ago. It is testament to the brilliant installers and to the technology getting better. More in our recent paper: www.sciencedirect.com/science/arti...

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James Hansen @drjamesehansen.bsky.social · 10/11/2025

I have been notified that the video link to my Helsinki talk does not work for some people. Here's an alternative link for those who prefer a YouTube version: youtu.be/D2abyXGvELI

youtu.be

James Hansen - Climate Reckoning in ATLAS25, Operaatio Arktis, Helsinki, Finland

YouTube video by Climate Science, Awareness and Solutions

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James Hansen @drjamesehansen.bsky.social · 18/12/2025

Let’s see what we can learn from temperature change in the next two years – mailchi.mp/caa/global-t... Also available on Substack: jimehansen.substack.com/.../global-t....

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Leon Simons @leonsimons.com · 21/12/2025

Based on the 11-year running mean (and on Earth's Energy Imbalance), the near-term rate of warming could turn out much higher than the linear 2010-2025 extrapolation. The next El Niño peak will be very informative for the rate of global warming, as @drjamesehansen.bsky.social points out:

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Trystan Lea @trystanlea.bsky.social · 21/12/2025

Thanks @janrosenow.bsky.social it's been great to work with you on this! Thank you for making the paper possible!

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Glyn Hudson @glynhudson.bsky.social · 18/12/2025

It's been great to be part of this project with @janrosenow.bsky.social @trystanlea.bsky.social to share the results from HeatpumpMonitor.org @openenergymon.bsky.social in a peer-reviewed paper 🥳 The overall highlighted HP performance is testament to the work of excellent installers 👏 🎉

heatpumpmonitor.org

HeatpumpMonitor.org - Heat Pump Performance Data

An open-source initiative to share and compare heat pump performance data. Join our community of heat pump owners sharing real-world performance data.

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Jan Rosenow @janrosenow.bsky.social · 18/12/2025

NEW RESEARCH: UK heat pumps can perform far better than many think. Our analysis of HeatPumpMonitor.org data shows well-designed systems achieve ~40% higher efficiency than past trials (SCoP 3.86 vs 2.81), cutting bills (~£224/yr) and emissions. Open access: www.sciencedirect.com/science/arti...

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Trystan Lea @trystanlea.bsky.social · 06/04/2025

Maybe less dramatic but there is a risk to undersize on newer build properties, especially where max output during defrost conditions doesn't match datasheet and if build quality is lower than design..

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Trystan Lea @trystanlea.bsky.social · 06/04/2025

Makes sense in building physics terms but if this just adds to over-inflated heat loss in pre-2000 properties then it's not helping. Key is to have good agreement between calculated and measured heat loss.

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Glyn Hudson @glynhudson.bsky.social · 30/03/2025

Big thanks to TBarton Electrical for doing an excellent job installing the solar and battery system, they've been great to work with tbartonelectrical.co.uk

tbartonelectrical.co.uk

T Barton Electrical | Solar, Home Battery and Electrical Installations and Service

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Trystan Lea @trystanlea.bsky.social · 29/03/2025

We will do a detailed comparison

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Trystan Lea @trystanlea.bsky.social · 29/03/2025

Performance on space heating has been great so far, COP 4. While a buffer was installed as per viessman spec, we also have the option to bypass the buffer and we've been running it with the buffer bypassed all on the primary circulation pumps just fine over recent days 👍

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Trystan Lea @trystanlea.bsky.social · 29/03/2025

It's been great to be part of this project. While most of the work is credit to Chris from Griffith's heating, Glyn and I did the heatloss calc and are involved in commissioning, optimisation and monitoring of course

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Trystan Lea @trystanlea.bsky.social · 29/03/2025

That's a great way of approaching it, always good to come at it from both angles, that should be part of standard heat loss calc methodology rather than relying on calculation alone

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Trystan Lea @trystanlea.bsky.social · 29/03/2025

Thanks Keith, all about a useful amount but not too much , thanks for picking these points up!

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Keith Alexander @keithalexander.bsky.social · 26/03/2025

When I was getting our heat pump here, because of the twitter heatpump discourse, I was worried that our model was oversized, but found in practice that it actually performs very well! (It's well within @openenergymon.bsky.social's range of useful oversizing).

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Glyn Hudson @glynhudson.bsky.social · 26/03/2025

Heat pumps are running! Still lots of tweaking and tidying to do but building is heating up 😁

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Glyn Hudson @glynhudson.bsky.social · 26/03/2025

30kW SolarEdge PV and 65kWh of GivEnergy Commercial battey system is now up and running, with @openenergymon.bsky.social monitoring 😀

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Trystan Lea @trystanlea.bsky.social · 11/03/2025

Yes that's correct, weather comp for boilers has not been widely adopted or mandated as is the case elsewhere.

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Trystan Lea @trystanlea.bsky.social · 10/03/2025

That's a great result! it would be great to see more of an industry push to include weather compensation with boilers , it would help get people more familiar with heatpump controls as well

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Trystan Lea @trystanlea.bsky.social · 10/03/2025

4. Our analysis of heat pump max outputs during defrost conditions is available here docs.openenergymonitor.org/heatpumpmoni... and discussion of how much margin is good to add and how to avoid oversizing here docs.openenergymonitor.org/heatpumpmoni...

docs.openenergymonitor.org

Max output testing under defrost conditions — OpenEnergyMonitor 0.0.1 documentation

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Trystan Lea @trystanlea.bsky.social · 10/03/2025

3. There are risks to accurate heat loss, if your using a design temp of 50C and improving heat loss calc process, consider lowering design flow temps to nearer 40 and add a margin to cover lower than datasheet outputs during defrost conditions docs.openenergymonitor.org/heatpumpmoni...

docs.openenergymonitor.org

Heat loss — OpenEnergyMonitor 0.0.1 documentation

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Trystan Lea @trystanlea.bsky.social · 10/03/2025

2. The secret to making design temperatures of 40C (or lower in practice) possible is accurate heat loss calculation and tuned weather comp docs.openenergymonitor.org/heatpumpmoni...

docs.openenergymonitor.org

Heat loss — OpenEnergyMonitor 0.0.1 documentation

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Trystan Lea @trystanlea.bsky.social · 10/03/2025

1. Low flow temperatures = high performance (heatpump 101) but did you know high performance heatpump often run at around 34C on the coldest days? docs.openenergymonitor.org/heatpumpmoni...

docs.openenergymonitor.org

Low flow temperature = High performance — OpenEnergyMonitor 0.0.1 documentation

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Trystan Lea @trystanlea.bsky.social · 10/03/2025

We've written up the main findings from HeatpumpMonitor.org so far here docs.openenergymonitor.org/heatpumpmoni..., presenting this tomorrow at the DESNZ/IEA heatpump research seminar 🤓

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Glyn Hudson @glynhudson.bsky.social · 27/02/2025

Solar PV install is coming along, only another 43 panels to go! 🥵⚡

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Glyn Hudson @glynhudson.bsky.social · 26/02/2025

I really enjoyed this episode of the @TransitionShow.mastodon.energy.ap.brid.gy podcast with @richardlowes.bsky.social, thanks for the @openenergymon.bsky.social heatpumpmonitor.org mention, "brings an element of fun into heatpumps" 😁

heatpumpmonitor.org

HeatpumpMonitor.org

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Glyn Hudson @glynhudson.bsky.social · 14/02/2025

Here's a video about an interesting ASHP installation I was involved with in a solid stone cottage, the combination of insulation, air tightness, UFH and MVHR has made for a very efficient low-cost heating system with a SCOP of 5.1 for space heating 😀 📈 youtu.be/YouOLThHSNk?...

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Glyn Hudson @glynhudson.bsky.social · 17/02/2025

This is part of a big electrification and decarbonisation project for the building to remove deoendancy on LPG, reduce running costs and increase energy security; this will involve 2x 16kW Viessmann ASHP cascade, 69kWh of GivEnergy storage, 30kW of PV and @openenergymon.bsky.social monitoring 😀

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Glyn Hudson @glynhudson.bsky.social · 19/02/2025

More panels going up! Only 60 more to go 😅

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Glyn Hudson @glynhudson.bsky.social · 17/02/2025

I've been helping out on a solar PV installation on our @Openenergymon shared office space, it will be a 30kW SolarEdge array! Today we fitted the rails and got the first couple of panels in place 😁

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Glyn Hudson @glynhudson.bsky.social · 19/02/2025

This Skill Builder heatpump now one of the best performing systems in the country thanks to a Heat Geek transformation! Here's the live and historic data monitored independently by @openenergymon.bsky.social 👏 heatpumpmonitor.org/system/view?...

heatpumpmonitor.org

HeatpumpMonitor.org

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Glyn Hudson @glynhudson.bsky.social · 07/02/2025

Big update incoming for OpenVehicles (OVMS) Android app 😍

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Glyn Hudson @glynhudson.bsky.social · 02/02/2025

Interesting podcast about the Electrification Of Heat government heat pump trial results with Katrina Young from @energysyscat.bsky.social and @trystanlea.bsky.social from @openenergymon.bsky.social

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Cllr Owen Burbidge 🔶 @oburbidge.bsky.social · 27/12/2024

It’s 4C outside and the ASHP is nearly hitting a COP of 5 😍😍😍 It’s been running continuously since 1320 yesterday despite there being mist and high humidity! #HeatPumpsWork!

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