Octopus Heat Pumps

Spies

When I had an ev charger put in I had to do my own DNO notification, when they asked for max theoretical draw i put it as 58a because over 60a it would require something extra to be done.

They emailed back very quickly to say it was fine. 

murmeltier

koru said:

murmeltier said:

As an aside and much to my amazement no heat loss calculation was done. Instead the Swiss installer took their annual gas usage, divided it by 3 and used that to size & install the heat pump. Total cost ca £35k after government grant ... 

You mean divide by 3000? Interestingly, this is pretty much the rough estimate method suggested by Michael de Podesta, as summarised in the fabulous essay on heat loss here: https://energy-stats.uk/what-size-heat-pump/

Yes, divide by 3000, sorry. Thanks for the link, hadn't seen that one yet.

Gerry1 said:

murmeltier said:

I meant gas usage of 2.5kW per hour to keep the house at set temperature (~17 degrees) while outside conditions unchanged (~0 degrees). I've observed this usage on multiple occassions this winter. Obviously very crude estimate, so even if true figure is higher, I can't see it ever getting to 10kW.

Do you really think that switching off the central heating and plugging in just one 3kW fan heater would keep the whole house warm when it's freezing outside?

No. But I'm trying to convince myself that I'm better off with a smaller heatpump than the 10.6kW Octopus want to put in, and no matter what approximation/formula/data/calculation I use, 10.6kW is too much. 
 

koru

matt_drummer said:

The 11kW is the same as the 9kW and the 14kW and the 16kW. It makes little difference which one you have. ...

They all have the same minimum output of around 4kw.

So 4kW of heat on a warm day is good in a house that needs 16kW on a cold day, but not so great in a house that only needs 9kW on a cold day.

The 9kw has a very narrow range of outputs compared to many other heat pumps.

Matt, can you point me to the source of this minimum output of 4kW for the 9kW Daikin? I'm not doubting you, but I'm struggling to find any specs that show anything except the maximum output. And do you know of any specs for the minimum output of the 8kW model?

The reason I ask is that I'm looking at the specs for the Vaillant Arotherm 7kW, which does seem to have figures for minimum output (page 46 here: https://www.vaillant.co.uk/product-images/0020330791-03.pdf.pdf). But I'm a bit surprised to see that the minimum seems to be 3.0kW. If the typical ASHP modulates down to a quarter of the maximum I would have expected the Vaillant 7kW to modulate to less than 2kW.

So, I'm now wondering if the Daikin 8kW would actually modulate to lower than the Vaillant 7kW.

Edit: maybe I've found it. I found a 'data book' here: https://solar-distribution.baywa-re.pl/out/media/1_-_Daikin_Altherma_3M_EDLA(04-08)E3V3_E(B-D)LA04-08E(3)V3_Data_Books_EEDEN22A_English.pdf
Is it the pdh figure on page 20, which is 3.3kW? (Surprisingly, that's at 7C outside and the pdh at 12C increases to 4.1kW.)

matt_drummer

My source is the data from mine and other heat pumps.

You can view many different heat pumps on heatpumpmonitor.org

Choose the MID metered systems and you can look at them all and see how they perform.

In my house the 8kW runs well at a minimum of between 2,000w and 2,500w 

Much below that it is not that happy or as efficient.

I think you may misundertand my use of minimum.

The 9kW Daikin will output 3,500w or even less if you want it to.

The problem is that it still uses 900w of electricity to do this as a minimum. No problem though as long as you can accept the lower efficiency. 

I believe the 7kW Vaillant is more like a 9kW heat pump in reality.

But you can look at Vaillant heat pumps on heatpumpmonitor.org too and see for yourself.

rjmachin

Update on my Octopus Heat Pump installation journey....

Timeline:
17th October 2023 - Got a heat pump quote for £1610
21st October 2023 - Paid £500 deposit
20th November 2023 - Advised due to high demand, there is a delay and are hiring more installers
1st March 2024 - Survey took place for heat pump
5th March 2024 - Signed Final Sales Agreement of £1360 (due to Daikin £250 discount) with £860 balance due on completion
11th March 2024 - New EPC carried out as our had expired
13th March 2024 - DNO reject application unless limiting car charger changed to a load limiting car charger.
5th April 2024 - Car charger swapped to a Zappi (cost £999.60 installed)
10th April 2024 - Pre-Instal Visit by install team leader to check over the plans
29th April 2024 - DNO approve application for heat pump
20th-24th May 2024 - Installation of heat pump
21st May 2024 - Removal of gas meter

I was very impressed with the installation teams (electricians team and heat pump team), and the team leader was really good, arrived first every day at 8am and kept us fully up to date all week and explained how things work.

The heat pump was commissioned on Thursday

There was an error showing Thursday night, H7-01 and H7-05 relating to the water flow, but both the team leaders (inc electrician) were coming back Friday to check over things, so they had a look and the issue was the filter had the "gunk" that was used when soldering the pipes for the radiators and a valve was in the wrong position, so they resolved that issue and it's now all working.

I am expecting a request next week for the outstanding £860 balance.

Of course, I did have to pay the £999.60 for the new car charger, but it has enabled me to start using Intelligent Octopus Go, with longer and cheaper overnight rates than standard Go, and I have used the smart charging a few times which gave me even more cheap rate slots, so I think it was a worthwhile investment.

I now need to spend the next few weeks/months tweaking the settings to get the best efficiency, but so far, I am very happy.

michaels

Is there a charge to have the gas supply disconnected?  thanks

Netexporter

Octopus remove the gas meter, and cap the supply, for free. Eventually the supply pipes might be deemed unsafe but I'm not sure who picks the bill up for removing/disconnecting them.

Reed_Richards

rjmachin said:

Of course, I did have to pay the £999.60 for the new car charger, but it has enabled me to start using Intelligent Octopus Go, with longer and cheaper overnight rates than standard Go, and I have used the smart charging a few times which gave me even more cheap rate slots, so I think it was a worthwhile investment.

Completely off topic but I have a bugbear about car chargers.  Have you worked out how many kWh you will have used before the money that you saved using the new car charger will sum to £999.60?

Netexporter

Depends what tariff you are on and your driving habits. Somebody with a long daily commute might need more charge than a granny charger can provide in a 4 or 6 hour overnight low-price window. Also, people on Agile can get paid three times a much when stashing leccy during a plunge period.

rjmachin

I use around 50-60 kWh per week commuting to work, some weeks we go on ParkRun Tourism trips, so will nearly double that to 100-120 kWh.

I was previously on Octopus GO at 9p per kWh, so from that cost to 7.5p, I would save:
£0.75 to £0.90 per week for just commuting
or, £1.50 to £1.80 per week for just commuting and trips

However, it also gives an additional 2 hours at 7.5p/kWh instead of 26.37p/kWh, which I am not able to quantify as it is variable.

I can also now plug in the car earlier in the evening and if a charging slot is added before the started 6 hour slot, the whole house gets that energy at the cheap rate too.

Purely based on the commuting charging and nothing else, it would take me around 21 years to make back the investment in the charger, but I think in reality it will be a lot less than that.