The only way to convince my Mrs is to highlight the cost savings. I go fully equipped with numbers like I would go to a CFO with RoIC stats and a DCF model, without which it won't be approved at my home.

I don't mind my home being a power station, as long as it's not using coal or gas!

Posted by: @kevh

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As my wife reminds me, this is my home and not a power station.

Posted by: @colinc

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@jamespa I don't believe I have said anything other than attempt to make some light of this.

I am not going to take any lecture, or warning, from anyone about how I cast my vote.

I note that your intention was to 'make light' and apologise that I thought that some might interpret your comment as serious even if that was not how you intended it.  My comments were intend for those who might interpret it as serious, not for those who like did not intend or do not take your post seriously.  I accept I should have made that clearer

Posted by: @colinc

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Best for everyone if you would stick to where your contribution is valued, viz. imparting your scientific knowledge to a Renewable Heating Hub forum

You are as entitled to an opinion as I am, and vice versa. 

If the facts (as best we can ascertain them) are at variance with my opinion, then I will revise my opinion. I will not knowingly seek to obscure the facts.

I will make no apology for 'wordsmithing' contributions even if you personally find that objectionable. 

Posted by: @kevh

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Posted by: @jamespa

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Posted by: @kevh

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As an example, my teeny 5kWh battery saw us through winter at an average cost of around 14-15p /kWh, easily outpacing what we would have spent on gas (calculated by direct comparison to last winter and also comparing the Cosy9 output to current gas prices at a SCOP of 3.66).  

Thats impressive, I averaged about 20.  I have been assuming I need a largeish battery (10-15kWh) but maybe I should re-evaluate the Cosy option with a smaller one!

 

Bear in mind that my maximum daily draw over winter was a tad under 50kWh, typically it was around the 30kWh mark, which the battery took the sting out of.

If you have an EV I am sure your daily draw will be much higher, hence maybe a larger capacity battery might suit your circumstances better.

Personally I doubt that in my circumstances I would be any better served by a larger capacity battery at present, although that doesn't stop me eyeing them up when I read of the huge solar exports that some achieve.  As my wife reminds me, this is my home and not a power station. 🤣    

 

 

Thanks that's helpful.

Mentally I discount the EV because it can be charged in cheap periods without recourse to a secondary battery.  However sweating  the battery asset using cosy and doing 3 cycles a day is something I have not yet built into my modelling.  So the fact you find this beneficial is a useful spur to some more modelling.

@jamespa I definitely made full use of the Cosy tariff and cycled thrice a day. But, I was a bit concerned, as unlike Tesla batteries Growatt doesn't offer unlimited cycles warranty. So, decided to double the battery capacity and switch to Go. This winter we just cycled once a day but still cost similar to last year on Cosy. If cycling is a concern, you can also model a scenario where you don't charge the battery during the 10 pm to 12 am period, but just pump up the heat and setback during the 12 am.to 4 am period. But the 1 pm to 4 pm slot can be used to charge the batteries and avoid touching the grid after 4pm.

Posted by: @jamespa

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However sweating  the battery asset using cosy and doing 3 cycles a day is something I have not yet built into my modelling. 

Posted by: @chandykris

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@jamespa I definitely made full use of the Cosy tariff and cycled thrice a day. But, I was a bit concerned, as unlike Tesla batteries Growatt doesn't offer unlimited cycles warranty. So, decided to double the battery capacity and switch to Go. This winter we just cycled once a day but still cost similar to last year on Cosy. If cycling is a concern, you can also model a scenario where you don't charge the battery during the 10 pm to 12 am period, but just pump up the heat and setback during the 12 am.to 4 am period. But the 1 pm to 4 pm slot can be used to charge the batteries and avoid touching the grid after 4pm.

Posted by: @jamespa

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However sweating  the battery asset using cosy and doing 3 cycles a day is something I have not yet built into my modelling. 

 

I admit that the Cosy tariff encourages a bit of battery thrashing and I fully engaged in that with eyes wide open.  I could not afford the switch to an ASHP without doing so, unless I added a second larger battery.  

That raises a question however, as I would lose the warranty on my battery / PV install by doing so, and given that the battery/inverter is GivEnergy, I might just need that Octopus lifeline should something go awry. Oh, and who would touch a GE inverter anyway.  Hmm.

I was showing a friend around all our renewable tech today who is interested in switching to a HP. What you are doing is the advice I essentially gave him as well. If one is installing a HP, ideally go with a battery storage system as well and switch to a tariff like Cosy to bring down the cost of heating in the winter. He doesn't have an EV yet, so no point in maxing out on the battery storage.. Rather go for a decent size battery and stick to Cosy and its three off-peak slots.

If one is looking at maximum emissions cutting, then HP is the best option. If one is looking for maximum RoI, then HP plus batteries. If one is keen on self sufficiency, then go for a PV array on top.

Posted by: @kevh

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I could not afford the switch to an ASHP without doing so, unless I added a second larger battery.

@chandykris 

It may be worth getting an EV charger nonetheless and go overnight.. 😎  

@batpred Yes, that could work and I have offered to charge my car once a month for like an hour if Octopus do check for patterns in usage. Having said that, once he gets on the renewables journey, he may end up buying an EV anyway.

I started with an EV, and once I realised that there's cheap electricity for like 5 hours a day, automatically I started exploring how to store that energy and use later in the day. That led me to installing batteries, then get solar panels and within a few weeks started looking at a HP.

Posted by: @chandykris

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@batpred Yes, that could work and I have offered to charge my car once a month for like an hour if Octopus do check for patterns in usage. Having said that, once he gets on the renewables journey, he may end up buying an EV anyway.

I started with an EV, and once I realised that there's cheap electricity for like 5 hours a day, automatically I started exploring how to store that energy and use later in the day. That led me to installing batteries, then get solar panels and within a few weeks started looking at a HP.

I completely understand that progression.  I got solar panels in 2011, then an big gap, then an EV and heat pump in quick succession, and I'm not going back voluntarily with any of this.  Even ignoring environmental benefits its just better technology, at least for us.  We do a fairly low mileage so don't even have a charger, just an EV rated 13A socket.

I will probably eventually get a charger to benefit from Intelligent Go (or when they insist on it as a condition of a nighttime tarif), and a battery when I can make the business case work (its somewhat scuppered by the fact I already have a working solar inverter so cant assign any of the cost to that). 

That said if energy prices continue at current levels, which seems highly likely given that orange one has got bored/decided to punish the world/whatever else the reason for this stupid war is - justifying a battery is easier.  

Posted by: @chandykris

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I started with an EV, and once I realised that there's cheap electricity for like 5 hours a day

Yes, it’s like the leftovers are our treasure! 

@batpred Who doesn't like bubble and squeak?!

@chandykris My wife’s rather restrictive diet means we have no green veg in the B&S I make; inventive measures have to be employed!!! Toodles.