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Energy tariffs and consumption fiddling to make my heat pump more cost efficient.

 
Electricity, Tariffs, Monitoring & Providers
Last Post by Anonymous 1 year ago
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 NetDonkey
(@netdonkey)
Estimable Member Member
Joined: 1 year ago
Posts: 56
Topic starter 10/09/2024 7:18 pm  

Hi all

I currently have the following which was installed in early June:

6.2kW Solar PV

6kW Solis Inverter

5kW Puredrive/Duracell Battery

8kW Samsung r290 ASHP

 

I have signed up with Octopus Outgoing 12M fixed and Agile Octopus incoming and so far it has been working well.  The battery for the most part has been fine but as the days are getting shorter it has started lack.  I have been manually setting the charge time through the Solis app to charge overnight recently when it has been decent pricing.

So far the ASHP has only been heating the water and we have yet to switch the heating on.  Previously, with our gas boiler, we would run this between 1pm-8pm to get to a temp of 19C which would take a couple of hours (yes I'm a tight Scotman 😀 ).  With the ASHP being installed we have also added underfloor insulation which I am hoping will also help with the temperature.

I suppose the questions i'm looking for answers/suggestions to within the above waffle is this:

  • With the lower water temp with the heating through the ASHP, is it worth setting this to come on earlier?
  • Would it be worth moving to something like the new Octopus Cosy or give it time over this winter to see what happens?
  • Looking to use Home Assistant to play around dynamic charge/discharge times. Would this be beneficial?
  • Would an additional battery help to make sure i'm not drawing from the grid between 4-8pm when energy is at it's most expensive? 

Thanks


This topic was modified 1 year ago by Mars

   
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 Anonymous 5011
(@Anonymous 5011)
Joined: 3 years ago
Posts: 562
10/09/2024 7:48 pm  

Posted by: @netdonkey
↑

With the lower water temp with the heating through the ASHP, is it worth setting this to come on earlier?

I would say it's better to just leave it running.  Open all the thermostats to max settings, get your weather compensation curve fine tuned to get a nice even temp in the house. After that look at a single small 1 to 2 Deg set back. Do not use your heat pump the same way as a boiler, you will hate your bills if your do.

Posted by: @netdonkey
↑

Looking to use Home Assistant to play around dynamic charge/discharge times. Would this be beneficial?

maybe not in winter your heat pump will gobble up the electric when temps drop outside, so charge fully when it's cheap. Yes for shoulder and summer months.


This post was modified 1 year ago by Mars

   
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 Gary
(@gary)
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Joined: 3 years ago
Posts: 350
11/09/2024 7:04 am  

Agree with John, forget how you used to run your boiler, last night it was between 7-10°C outside, my heat pump came on at 12am ran continuously for 6 hours with no cycling at 31°C flow temp, it raised the house temp by 0.1°C per hour and used 5kWh.  Don't let your house cool down too much overnight, when its subzero outside I don't use any setbacks its just counter productive the house will be to cold in the morning and then takes all day to heat back up when no-one is there.



   
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 NetDonkey
(@netdonkey)
Estimable Member Member
Joined: 1 year ago
Posts: 56
Topic starter 11/09/2024 8:11 am  

Thanks both.

@gary when you say set back, is this just changing the temp at a specific time?

 

Nick



   
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 Anonymous 5011
(@Anonymous 5011)
Joined: 3 years ago
Posts: 562
11/09/2024 8:39 am  

Posted by: @netdonkey
↑

Thanks both.

@gary when you say set back, is this just changing the temp at a specific time?

 

Nick

Yes. The ideal is you have flow temps just warm enough to keep the house at an even temp, via a compensation curve. A set back sounds good, but to get the house back up to temp requires a higher flow temp than steady state. So you end up chasing your tail. And get higher bills than necessary.

 



   
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 NetDonkey
(@netdonkey)
Estimable Member Member
Joined: 1 year ago
Posts: 56
Topic starter 11/09/2024 8:47 am  

Would this be something to do with the phrase ‘water law’ that the plumber was muttering?



   
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 Gary
(@gary)
Prominent Member Member
Joined: 3 years ago
Posts: 350
11/09/2024 8:51 am  

@netdonkey Yes water law is the term Samsung use for weather compensation curve.



   
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 Anonymous 5011
(@Anonymous 5011)
Joined: 3 years ago
Posts: 562
11/09/2024 9:06 am  

Make sure you can adjust once the plumber has gone, so get him to walk you through the settings 



   
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Majordennisbloodnok
 Majordennisbloodnok
(@majordennisbloodnok)
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Joined: 4 years ago
Posts: 1574
11/09/2024 9:08 am  

Posted by: @netdonkey
↑

Looking to use Home Assistant to play around dynamic charge/discharge times. Would this be beneficial?

Dynamic charging, yes definitely. You can get as clever as you want with a home automation system to ensure you charge at a cheaper rate than you then later consume.

Dynamic discharging, probably not. My experience is that if you're really clever with your calculating you could import at one rate and export at a higher one, but that the gain is less than you would get by holding onto that energy and using it yourself during an expensive import period later in the day. Once you're past the peak period early evening then any tinkering you could do will produce minimal results at the expense of extra charge/discharge cycles of the battery and therefore its earlier demise.

 

Posted by: @netdonkey
↑

Would an additional battery help to make sure i'm not drawing from the grid between 4-8pm when energy is at it's most expensive?

Yes it would but I doubt the benefit would on its own give you a return on its cost in a reasonable timeframe. That said, do the sums and you'll be able to make a decision.

 

Posted by: @netdonkey
↑

Would it be worth moving to something like the new Octopus Cosy or give it time over this winter to see what happens?

Quite possibly but Octopus' own comparison tools may well give you a clearer answer. At a guess I'd say your battery probably isn't quite big enough to make any difference all that significant. Obviously each tariff demands a different approach to consumption to make the most of it but I suspect you've already extracted the vast majority of the gain by switching to one of the intelligent tariffs and adjusting your consumption pattern accordingly.

 


105 m2 bungalow in South East England
Mitsubishi Ecodan 8.5 kW air source heat pump
18 x 360W solar panels
1 x 6 kW GroWatt battery and SPH5000 inverter
1 x Myenergi Zappi
1 x VW ID3
Raised beds for home-grown veg and chickens for eggs

"Semper in excretia; sumus solum profundum variat"


   
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 NetDonkey
(@netdonkey)
Estimable Member Member
Joined: 1 year ago
Posts: 56
Topic starter 11/09/2024 9:21 am  

@johnmo Yeah that was one of the first things I got him to show me.  I'll have a scan through the ASHP section to see if I can find an ideal for these settings.

 

@majordennisbloodnok noted.  I have seen additional 5kW puredrive batteries for ~£1600 so will do some mathing.



   
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 Anonymous 5011
(@Anonymous 5011)
Joined: 3 years ago
Posts: 562
11/09/2024 9:36 am  

Posted by: @netdonkey
↑

scan through the ASHP section to see if I can find an ideal for these settings.

Would not bother wasting your time, every house is different, what's right for next door may not be right for you.

Start point is 

Minimum allowed flow temp at 20 deg outside, the other end design flow temp and design outside temp. Get system running, only move the design flow temp to get room temps where you need them. Use the built in thermostat in the controller to help get your run times acceptable at low load periods (but only if your cycling rate on the heat pump is high). So run against the thermostat down to about 10 degs outside then pure weather compensation - Samsung have a setting for this I believe.



   
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