9kw Daikin performance

Hardware Heatpump
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1

Hi, first post. I had a 9kw Daikin installed by Octopus in February. Currently battling for a swap due to the minimum modulation issue and oversizing. I have made several changes to get it to behave reasonably. (Octopus are not happy about this and want me to run their settings) Unsure if I have the updated firmware….

I have a continuous 60% pump speed limit, a 2.5kw power limit, and weather curve set to 38C @ -3, alongside some home assistant automations that stretch run time by bumping up the target flow temperature when the return gets within 0.2C of the target, and others that turn the heat pump off and on dependant on internal temperatures / time of day.

My system id: 1164 (Ipswich)

Would really appreciate any feedback on how my system is running, I’m not an expert and this has been a steep learning curve.

Also, is there a way to calculate heat loss from the data?

Thanks.

2

People have reported that the 9kW firmware update drops the minimum input power to about 700W. Looking at your data you don’t drop below about 850W, so I don’t think you have it. Might be worth arguing.

There is a heat loss estimation tool on this site. I’m yet to master how to use it:

3

Hi Ali, thank you for the info. I will try to speak to Daikin and see if they can check.

If I am looking at the heat demand tool right, it looks like my heat loss is far less than calculated?

I need some definitive proof to show Octopus. I did a heat Punk survey which calculates the heat loss at 7.1kw. They calculated it at 8.2

4

Even at 7.1kW Octopus wouldn’t install the 8kW as they say that figure doesn’t take into account defrosts. I’d be surprised if they went with a swap unless you demonstrated a significant different between your heat loss and their calculation.

However, if I’m using the heat loss calculation tool properly, it appears to show your actual heat demand to be 5.67kW. Though you really need a full seasons worth of data here and you only have data for March and April.

How accurate is your power monitor? Your data shows a steady minimum input of about 846W whereas other 9kW devices are around 900W. Could it be under reporting?

5

Good luck with your Battle. I have a 9kW Daikin fitted by Octopus and have been trying to get it changed for 2 years. I have had an independent survey that shows the pump is oversized, also Daikin say it is oversized. Currently have a complaint lodged with Napit so awaiting the result of this. My advice is to you is to gather as much data as you can to prove your claim.

6

I am using a Shelly emPro. I think the lower power consumption is due to the pump speed limit I have enforced, it prevents the system getting saturated on startup when the pump is normally ramped up to full speed and it chucks a load of heat into the house unnecessarily.

Heat Punk recommends an 8kw unit, a 9kw unit that is able to modulate down low enough would be acceptable. The Daikin is not fit for purpose during the majority of the heating season, this is the angle I am trying to argue.

7

Thanks for the advice. What was your revised heat loss figure, if you don’t mind me asking?

There doesn’t seem to be anyone available at Octopus who understands how heat pumps work or how much of a problem the minimum modulation issue is.

8

My HA yaml to decrease cycling when using LWT

alias: "Altherma: Smart Cycle Stretch (LWT) Incremental"

description: Increases LWT offset by +1 each time conditions are met, with a reset.

triggers:

  - trigger: template

    value_template: >

      {% set inlet = states('sensor.inlet_water_temp_r4t') | float(0) %} {% set

      setpoint = states('sensor.lw_setpoint_main') | float(0) %} {{ (setpoint -

      inlet) <= 0.3 and inlet > 0 }}

    id: increase_offset

  - trigger: numeric_state

    entity_id: sensor.shellyproem50_6825ddd11228_energy_meter_1_power

    below: 100

    for:

      minutes: 1

    id: reset_offset

  - trigger: state

    entity_id: climate.altherma_leaving_water_offset

    to: "off"

    id: reset_offset

  - trigger: homeassistant

    event: start

    id: reset_offset

  - trigger: time

    at: "06:00:00"

    id: reset_offset

  - trigger: time

    at: "21:00:00"

    id: reset_offset

conditions: \[\]

actions:

  - choose:

      - conditions:

          - condition: trigger

            id: increase_offset

          - condition: state

            entity_id: climate.altherma_leaving_water_offset

            state: heat

          - condition: state

            entity_id: binary_sensor.3way_valve_on_dhw_off_space

            state: "off"

            for:

              minutes: 2

          - condition: state

            entity_id: binary_sensor.defrost_operation

            state: "off"

            for:

              minutes: 2

        sequence:

          - action: climate.set_temperature

            target:

              entity_id: climate.altherma_leaving_water_offset

            data:

              temperature: >

                {% set current =

                state_attr('climate.altherma_leaving_water_offset',

                'temperature') | float(0) %} {% set hour = now().hour %} {% if

                hour >= 21 or hour < 6 %}

                  {{ \[current + 1, 1\] | min }}

                {% else %}

                  {{ \[current + 1, 4\] | min }}

                {% endif %}

      - conditions:

          - condition: trigger

            id: reset_offset

        sequence:

          - action: climate.set_temperature

            target:

              entity_id: climate.altherma_leaving_water_offset

            data:

              temperature: |

                {% set hour = now().hour %}

                {% if hour >= 21 or hour < 6 %}

                  -2

                {% else %}

                  0

                {% endif %}

mode: restart

THIS IS COUPLED WITH TWO OTHER AUTOMATIONS THAT PREVENT OVER HEATING / COOLING, DAY / NIGHT

alias: "Altherma: Day Thermostat (21 - 21.5)"

description: Handles both ON and OFF for daytime

triggers:

  - trigger: numeric_state

    entity_id: sensor.indoor_ambient_temp_r1t

    above: 21.5

    id: too_warm

  - trigger: numeric_state

    entity_id: sensor.indoor_ambient_temp_r1t

    below: 21

    id: too_cold

  - trigger: time

    at: "05:00:00"

    id: schedule_start

  - trigger: time_pattern

    minutes: /15

    id: schedule_start

  - trigger: homeassistant

    event: start

    id: schedule_start

conditions:

  - condition: time

    after: "04:59:00"

    before: "21:00:00"

actions:

  - choose:

      - conditions:

          - condition: or

            conditions:

              - condition: trigger

                id: too_warm

              - condition: template

                value_template: >-

                  {{ states('sensor.indoor_ambient_temp_r1t') | float(0) > 21.5

                  }}

        sequence:

          - action: climate.set_hvac_mode

            target:

              entity_id: climate.altherma_leaving_water_offset

            data:

              hvac_mode: "off"

      - conditions:

          - condition: or

            conditions:

              - condition: trigger

                id: too_cold

              - condition: trigger

                id: schedule_start

          - condition: template

            value_template: "{{ states('sensor.indoor_ambient_temp_r1t') | float(0) < 21 }}"

        sequence:

          - action: climate.set_hvac_mode

            target:

              entity_id: climate.altherma_leaving_water_offset

            data:

              hvac_mode: heat

mode: restart


alias: "Altherma: Night Thermostat (20.0 - 20.5)"

description: Handles both ON and OFF for nighttime

triggers:

  - entity_id: sensor.indoor_ambient_temp_r1t

    above: 20.5

    id: too_warm

    trigger: numeric_state

  - entity_id: sensor.indoor_ambient_temp_r1t

    below: 20

    id: too_cold

    trigger: numeric_state

  - at: "21:00:00"

    id: schedule_start

    trigger: time

conditions:

  - condition: time

    after: "21:00:00"

    before: "05:00:00"

actions:

  - choose:

      - conditions:

          - condition: or

            conditions:

              - condition: trigger

                id: too_warm

              - condition: template

                value_template: "{{ states('sensor.indoor_ambient_temp_r1t') | float > 20.5 }}"

        sequence:

          - action: climate.set_hvac_mode

            target:

              entity_id: climate.altherma_leaving_water_offset

            data:

              hvac_mode: "off"

      - conditions:

          - condition: or

            conditions:

              - condition: trigger

                id: too_cold

              - condition: trigger

                id: schedule_start

          - condition: template

            value_template: "{{ states('sensor.indoor_ambient_temp_r1t') | float < 20.0 }}"

        sequence:

          - action: climate.set_hvac_mode

            target:

              entity_id: climate.altherma_leaving_water_offset

            data:

              hvac_mode: heat

mode: restart
9

Our 9k Daikin was installed just over a year ago so I now have a full years data (via emonCMS and HA) and have just put a full report together showing a measured heat loss demand of less than 6kW.

I began pushing back on the install in April/May last year but only had minimal data of course. In July, I agreed to run through the winter to explore more but of course, as with everyone else with the 9k, the cycling continued.

I’m waiting for a response currently.

Incidentally, from a host of threads here and elsewhere, I found the best settings for our situation has been:

60% pump speed (not just on sampling)

Quiet mode throughout

Emitter type set to either Radiators or Underfloor

Control set to LW

WDC set to slope-offset 15/3 (15/2 for underfloor emitters)

Delta T set at 10 (or fixed at 8 for Radiators)

As many have found, each install situation is individual so what works for mine may not for others. I’ve spent months trying various options - 1 adjustment at a time - to arrive at my settings.

I know that others have been able to argue their case for downsizing successfully but I’ve not found the magic words to use .. so far

10

Incidentally, this is why I’ve settled on these settings

IMG_7145
IMG_71451284×1546 132 KB
The lower pump and fan speeds reduce the input floor without compromising heat output. The high delta T setting slows the power ramp up, on call for heat and reduces defrosts. Obviously it is not very cold today (around 10 degrees) but this seems to work for colder weather too (tested down to 2 degrees)

11

My independent survey show heat loss at 5.56kW. This is my graph from HeatPumpMonitor.

Screenshot 2026-04-16 at 08.48.22
Screenshot 2026-04-16 at 08.48.222732×1374 473 KB

12

Thanks, I suspect I will need to get some solid winter performance data before I can put together a solid case.
I can’t see how Octopus can argue with your data. I am starting to think that there is enough people having the same issues with oversizing and minimum modulation that a group case/legal action could be put together. MCS should be taking action on this.

13

This is really interesting. What COP are you getting with these settings?
I take it you have the revised firmware with the input power being that low?
I am waiting to hear back from Daikin on getting mine updated.

14

Heating sits around 4.5, DHW around 2.7

I presume so but I’m not sure which the updated version is

Good luck and keep us updated

15

I have found the input power limit has had the biggest impact on DHW COP for me. Takes a bit longer to heat the tank, but more efficient.

Screenshot_20260416_171641_Chrome
Screenshot_20260416_171641_Chrome1080×2340 190 KB

16

Thanks for that. I have the input limited but not as low as your 2.5k. Once I’m through my latest testing phase, I’ll try this out

17

I have just looked at your data.

Apart from using EspAltherma (I assume?) I see no issues.

On what grounds do you think the heat pump should be replaced?

It heats your house adequately, the efficiency exceeds that required by the MCS and you haven’t had any really cold days yet.

You will not convince Octopus to swap on the basis that you could get a higher SCOP with a different heat pump.

18

​Hi Matt,
​Thanks for taking the time to look at the data, I really appreciate the feedback.
​To answer your question on the grounds for a swap: my concern isn’t actually that the house is cold (it’s performing adequately, as you noted), but rather the fundamental mismatch between the unit’s hardware “floor” and the building’s load.
​As a Daikin 9kW (EDLA09), my unit is on the High Capacity chassis (a software-limited 16kW machine). The technical data shows its minimum heat output is ~3.5kW. However, based on my refined heat loss calculations (and confirmed by my real-world monitoring), my house demand at 10-12°C is only ~2.2kW.
​Because 3.5kW is > 2.2kW, the unit is mathematically incapable of steady-state modulation in milder weather. The only reason my data looks “reasonable” right now is because I’ve spent weeks implementing Home Assistant logic to artificially “bump” flow temperatures and stretch run times, and drastically limited the heat pumps settings. Without these manual interventions, the unit defaults to chronic 15-20 minute short-cycling.
​My argument for the swap to the 8kW (EDLA08) is that it belongs to the Low Capacity chassis. It provides the same design capacity for my cold-weather days (~7.5kW) but has a much lower modulation floor (~1.8kW). This would allow the system to run as a truly modulating inverter unit rather than a “pulsing” oversized one.
​I totally take your point that Octopus will be hard to move on SCOP alone. My strategy is to frame it as a hardware selection error—using a “Large Chassis” for a “Small Chassis” load, which prevents the system from operating “as designed” without unauthorized homeowner intervention.
​Does that logic hold up from your perspective, or am I overestimating the benefit of that lower modulation floor?
​

19

Firstly, I assume you are aware of my history?

I have had a 9kW replaced with an 8kW and I am fully aware of how both work and their specifications.

Where is your internal temperature coming from in your fdata?

You are extending run times with HA involvement but your house isn’t over heating.

Why not if the heat pump you have is unsuitable?

Why are you trying to stretch run times if the heat pump produces more heat than you need?

My house was like a sauna at minimum output and I was controlling the temperature indoors using windows and doors.

Most owners have heat pumps that cycle in warmer outside temperatures, its normal.

If your heat loss is around 7kW you’ll be struggling even with the 9kW when you need it, you should have had an 11kW seeing it is the same unit.

An 8kW Daikin is not the answer, it won’t provide enough heat when you need it.

As you are so adept with HA why don’t you just use that to control the hysteresis rather than the `useless’ Madoka?

There was a very specific reason why my heat pump was swapped and it involves a heated conservatory that should never have been. The heat loss of my house is about 3 kW and the conservatpry is about 1.5kW.

Even so, I would still prefer the 9kW over the 8kW if I could control the hysteresis more tightly than the Madoka offers, the 9kW is a better heat pump.

As I see it, you have no grounds to force a swap, you may prefer something else but there isn’t anything actually wrong with what you have. So far, it is just buyers remorse.

Sorry but that is my opinion

20

I appreciate you sharing your experience, especially having lived with both the 9kW and 8kW units. It’s really interesting to hear that you find the 9kW the “better” pump, and I take your point that in very cold weather, that extra headroom is a comfort.
​Regarding the “sauna” point, the reason my house isn’t overheating is simply because I’ve spent a lot of time “taming” the unit. I’m currently using a 2.5kW power limit and Home Assistant to force the unit off once the rooms are up to temperature. If I ran it on Octopus’s suggested settings (50°C flow with standard hysteresis), it would definitely be overshooting. My goal isn’t to stretch run times because I want more heat, but because I want the unit to provide that heat as a steady, efficient “trickle” rather than in high-power pulses.
​The crux of my concern is exactly what you mentioned regarding your own home. You have a total heat loss of ~4.5kW, so even the 8kW unit (with its ~1.8kW floor) is still a bit large for your mild-weather demand. However, my design loss is ~7kW. For my home, the 8kW unit’s modulation range (1.8kW to 7.5kW) would cover almost my entire heating season without needing to cycle. In contrast, the 9kW unit’s floor (~3.5kW) is higher than my demand for about 90% of the year.
​I’m not looking for a swap because of “buyer’s remorse,” but because I’m trying to move from a hardware platform designed for much larger loads to one designed specifically for my house’s size.
​I definitely agree with you on the Madoka, though! Relying on HA to manage the hysteresis is currently the only thing keeping the system running reasonably. I just feel that for a professional install, the hardware shouldn’t require that level of “aftermarket” logic to stay within a healthy operating window.
​Thanks again for the insight, it’s given me a lot to think about regarding how I manage the unit if a swap doesn’t happen.
​Best,
Sam