Octopus, did i imagine this?

[SteamyTea]

9 hours ago, sharpener said:

And I thought the physical installation of the HP was the major milestone.

 

[Bob Dylan's Talkin' New York; Verse 7]
Now, a very great man once said
That some people rob you with a fountain pen
It don’t take too long to find out
Just what he was talkin’ about
A lot of people don’t have much food on their table
But they got a lot of forks ’n’ knives
And they got to cut something

[JoeBano]

Octopus agile for me, average 17p/kWh for the last full year. I could probably get it cheaper if I cut down my energy usage in the expensive period 5-7pm but I’m not bothered my energy bill is around 30% cheaper than my gas neighbours. 

[ReedRichards]

11 hours ago, JamesPa said:

A 5kW battery in addition saves perhaps another £200-300, which if the battery costs 5k doesn't make a financial case. 

 

But does it cost that much?  This company is selling a 15.5 kWh battery for £2,500: https://www.fogstar.co.uk/products/fogstar-energy-15-5kwh-48v-battery

Edited October 18 by ReedRichards

[JamesPa]

3 minutes ago, ReedRichards said:

 

But does it cost that much?  This company is selling a 15.5 kWh battery for £2,500: https://www.fogstar.co.uk/products/fogstar-energy-15-5kwh-48v-battery

The installed prices I have found by a quick search suggest that 5k for 5kWh isnt far out.  I don't have recent quotes, when I did try some while ago found it quite difficult to get battery quotes without solar or vice versa.  

Like all products in this sector it seems installed prices bear little resemblance to the product price.  DiY is clearly an option to consider!

 

Edited October 18 by JamesPa

[JohnMo]

54 minutes ago, JoeBano said:

Octopus agile for me, average 17p/kWh

That's interesting, so slightly more than my simple E7 tariff. If I wasn't paying the standing charge for gas my figure comes down to 15p/kWh. 

 

But I assume yours is without battery? If that's the case having a smart meter (ours doesn't work) is a real money saver and would make a battery maths hard to justify.

[JohnMo]

2 minutes ago, JamesPa said:

5k for 5kWh isnt far out

I paid £8k for 13.5kWh (usable) full MCS certified install a year ago and prices have reduced since then.

[S2D2]

I paid £2k extra for a 3kWh battery MCS install at the same time as solar. It was the only battery option with less than a 10 year payback at the time. I have a thread on sizing it based on smart meter data that may be useful.

 

Since they added the third cheap cosy period that tariff has been the winner with 5 hours overnight to charge the EV and never more than 6 hours between cheap periods which works pretty perfectly with the 3kWh battery.

[JamesPa]

11 hours ago, sharpener said:

 

I don't think they can. To date even my self-install has had a projected ten year payback.

 

E7 only gives you one go at charging the battery (though I did actually have a gap but it was only an hour so too short to use).

 

Cosy which as you say is as much a battery tariff as an HP one gives you 3 goes, quite widely spaced apart. It is early days and not really cold enough to tell but I think it will give me a better ROI than E7 did.

 

Octopus notified me today that my Outgoing Fixed tariff is now operational so it now makes sense to import at 12.11 p/unit and export as much as possible at 15p.

 

Victron s/w is optimised for battery charging from PV, which doesn't suit this strategy but they also have a Dynamic ESS upgrade. It has a Green mode which prioritises battery charging and self-consumption of the PV generation, and Trade mode which I am trying out - this is more aggressive and seeks to optimise the return by whatever means. Reviews of it are mixed so if it doesn't work for me I will have to write my own flows to do it in NodeRed.

 

And I thought the physical installation of the HP was the major milestone...

Thats very interesting and useful thanks.  

 

I currently have sufficient things going on in my life that I don't need a code writing/control system project, much as I would probably enjoy it. 

 

I have yet to get the HP installed, although that is hopefully now not far off.  At this stage a battery either has to pay for itself with very simple configuration, or Im not going to bother.  Once my HP is installed and well controlled, and my 2mm:1ft scale model of Helston Station a lot further forward than it is now (two to three years hence I expect), I might yearn for writing some code.  

 

@JohnMo  @S2D2 thanks for the figures.  I will get some up to date quotes and reassess against the above priorities!

Edited October 18 by JamesPa

[SteamyTea]

9 minutes ago, JamesPa said:

Helston Station

Closed now.

It is in an old folks home, you moving in?

[JamesPa]

7 hours ago, SteamyTea said:

Closed now.

It is in an old folks home, you moving in?

The goods shed is an old folks home.  The rather fine station building has unfortunately been demolished, which is a pity. 

 

I don't intend moving in, just making a model of it as it was in the 1930s.  So far I have done the trackwork, land profiling and station building (which doesn't have an ashp so I guess we are off-topic).

[SteamyTea]

18 minutes ago, JamesPa said:

station building

What are the U-values.

18 minutes ago, JamesPa said:

which doesn't have an ashp so I guess we are off-topic

Probably won't get planning permission anyway.

[JamesPa]

1 hour ago, SteamyTea said:

1 hour ago, JamesPa said:

station building

What are the U-values

Pretty poor.  Cardboard walls don't help.

[JoeBano]

On 18/10/2024 at 08:55, JohnMo said:

That's interesting, so slightly more than my simple E7 tariff. If I wasn't paying the standing charge for gas my figure comes down to 15p/kWh. 

 

But I assume yours is without battery? If that's the case having a smart meter (ours doesn't work) is a real money saver and would make a battery maths hard to justify.

No battery here. I need a new roof at some point it’s 90 years old and the rosemary tiles are starting to break up, so will look at solar and possibly an outdoor battery to save space then. We do use a lot of electricity around 20-25kWh a day 2 young kids washing machine is always on. 

[PhilT]

On 18/10/2024 at 07:52, JoeBano said:

Octopus agile for me, average 17p/kWh for the last full year.

 

On 18/10/2024 at 08:55, JohnMo said:

If I wasn't paying the standing charge for gas my figure comes down to 15p/kWh.

Are these numbers gross or net of solar usage/export? Useful to compare what others are achieving. I could probably do more to get my cost down

[JohnMo]

27 minutes ago, PhilT said:

Are these numbers gross or net of solar

Just recalculated it

14p per kWh, based cost paid to Octopus and total house electricity energy used from all sources.

 

Just calculating based on the imported energy alone and total cost is 19.8p.

 

The above includes my gas standing charge.

 

Without gas standing charge

It's 13p and 18.3p

 

No smart meter, so E7 or standard tariff are available to me - don't get paid for export.

 

Basing payback on a standard tariff of 25p and total house usage and what I would actually have pay, if no battery or solar, we are saving around £1200 per year. Total cost spent on PV and battery is pretty close to £10k, so close to 12 years payback, based on an awful PV production year due to rain most days.

 

[PhilT]

4 hours ago, JohnMo said:

Without gas standing charge

It's 13p and 18.3p

So includes the electricity standing charges and 5% VAT, or not?

[JohnMo]

9 minutes ago, PhilT said:

So includes the electricity standing charges and 5% VAT, or not?

 

Fully inclusive billing amount including electricity standing charge and any Vat applicable.

[PhilT]

On 17/10/2024 at 08:13, JamesPa said:

Probably so, but Octopus Cosy is really a battery tarrif not a heat pump tarrif.  If you don't have a battery then I can't see it's useful to those with a heat pump.

I beg to disagree. If you already have a heat pump then Cosy makes financial sense without a battery. Getting a battery by itself just for Cosy would not be financially justifiable.

 

For a heat pump consuming say 3,000kWh pa there would be a potential maximum saving of (3,000 x 12p) = £360 pa, with no up front investment, having already bought the heat pump.

 

For a battery only, for an average consumption of 3,000kWh pa, the potential maximum saving would be the same at £360pa, but with a big up front investment. Considering the alternative use of your money at a few % interest on a fixed deposit account for 10 years after which you get all your money back, I would not consider getting a battery just for Cosy.

 

Happy to be challenged on this.

 

[Bramco]

If you have an insulated slab, PV and batteries, then Cosy would be an expensive way of doing things against Go Intelligent.  Export is 15p and import is 7p for 6 hours at night (might have changed a tad with the recent increase).

 

With an insulated slab, you can charge it at night on the 7p rate and it'll keep things toasty all day long, so no need for any boost during the day. The batteries and PV make sure you can get through the day without using any expensive peak time electricity.  So essentially all electricity is either free (PV) or 7p.  We also dump what's left in the battery just before the cheap rate and then re-load, so can benefit from the export/import rate differential.

 

Simon

[JamesPa]

2 hours ago, PhilT said:

For a heat pump consuming say 3,000kWh pa there would be a potential maximum saving of (3,000 x 12p) = £360 pa, with no up front investment, having already bought the heat pump.

 

If you only run the heat pump during the low rate periods then yes, but that will clobber the heat pump efficiency as you will need a higher flow temperature to deliver the same amount of energy.  And you have to offset any saving against the extra daytime/peak cost.  

 

Ovo currently offers 15p/kWh for the entirety of your heat pump consumption irrespective of time of day, provided you have the right heat pump.  I reckon that's unbeatable if you qualify, but also unsustainable for OVO

 

Edited October 23 by JamesPa

[SteamyTea]

1 minute ago, JamesPa said:

but that will clobber the heat pump efficiency as you will need a higher flow temperature to deliver the same amount of energy.

Does it though.

You can space the pipes closer and oversized the HP a bit.

Just a case looking at all the charts and seeing what falls out.

[JamesPa]

3 minutes ago, SteamyTea said:

Does it though.

You can space the pipes closer and oversized the HP a bit.

Just a case looking at all the charts and seeing what falls out.

Well yes (and no), if you haven't built the property yet!  But who is going to design a property to suit an electricity tariff that may or may not survive for any duration.

 

 I say 'and no' because, if the pipes are closer together, then your 'baseline' case is to run at the lower FT corresponding to the closer pipe spacing..

Edited October 23 by JamesPa

[SteamyTea]

11 minutes ago, JamesPa said:

who is going to design a property to suit an electricity tariff that may or may not survive for any duration

Well 7 million houses are on E7.

But I agree.

 

We have been told for a decade that ToU tariffs are coming, but all we get is a mishmash un-undetstable ones.

 

It is probably worth designing to have a house that can be heated for a day, in a 4 hour window though. PV can deliver quite well 2 hours either side of local noon.

[Bramco]

1 hour ago, JamesPa said:

but that will clobber the heat pump efficiency as you will need a higher flow temperature to deliver the same amount of energy.  And you have to offset any saving against the extra daytime/peak cost.  

 

 

 

Rubbish - ours runs at 35C and we don't run it during the day. So no impact on CoP or need for extra daytime/peak cost.  I did say, if you have an insulated slab......

 

And it's not about designing around a tariff, it's about designing and building an energy efficient home.  Working out which tariff is most cost effective is then pretty easy.

 

Simon

[JamesPa]

1 hour ago, Bramco said:

3 hours ago, JamesPa said:

but that will clobber the heat pump efficiency as you will need a higher flow temperature to deliver the same amount of energy.  And you have to offset any saving against the extra daytime/peak cost.  

 

 

 

Rubbish - ours runs at 35C and we don't run it during the day. So no impact on CoP or need for extra daytime/peak cost.  I did say, if you have an insulated slab......

 

And it's not about designing around a tariff, it's about designing and building an energy efficient home.  Working out which tariff is most cost effective is then pretty easy.

 

Simon

OK so we are talking very energy efficient newbuild. 

 

Even in this case there still is, at least in principle, a COP penalty (because you could, in principle, be running even lower than 35C) but, its relatively small - Instead of running at 35/30 you could, at least in principle, be running at something very roughly like 28/23, which would deliver very approximately the same energy on a 24/24 basis as 35/30 does on a 8/24 basis for an energy penalty of ~14%, which is certainly outweighed by the tarriff differential.   This is , I agree, a relatively small COP penalty on a relatively small consumption and anyway might not be practical within the engineering limitations of the heat pump, so in this case I can see that Cosy might work (although you do still need to offset the elevated price paid the majority of time for the other loads which, unless you have an EV, may well dominate the heat pump load in this case)

 

However Octopus don't solely sell to the tiny minority of people with highly energy efficient newbuilds, they also sell to the majority case of a house operating on radiators designed to operate at perhaps 45C with perhaps a 6-8kW load consuming ~6MWh/year for the heat pump.  In this case the flow temperature would need to be turned up to about 70C to deliver the same amount of energy in one third of the time.  In this, much more common, case, the efficiency would be clobbered (nearly doubled) unless you have a battery to extend the period at which you could operate on the low tarrif.

 

So, unless someone can prove me wrong, I will stick by my current analysis (actually stolen from @JohnMo who originally made the observation) that the Cosy tariff is basically, for the average person/house, a battery tariff.  Of course there are exceptions where it works in other circumstances, and you have quite possibly identified one.

 

Please don't take this as an argument for batteries.   I am doing the maths for me at present (I fit into the more typical retrofit category described above) and I have yet to find a scenario where batteries pay.  So far as I can see the best bet at present is the OVO heat pump add on, although I struggle to believe this will be around for long.  Failing that Intelligent Go seems (based on my current analysis) to be the next best as suggested by @Bramco, albeit in both cases without battery.  The battery payback analysis is based on £5K/9.5kWh or £7K/19kWh, which seems to be about par for the course at present unless you self install).  

Edited October 23 by JamesPa