I am about to have a Powerwall 3 fitted to help with the cost of running my heat pump. ( Ignore the capital cost of the battery!). I have no solar and intend to charge at the cheap Cosy rates and discharge during the standard rate times.
However, I saw a Youtube video yesterday which suggested that Octopus might be about to introduce a special Heat Pump tariff so that they can be run at the Cosy cheap rates 24/7.. If this turns out to be true, would there be any point in having the battery, apart from occasional Backup?
I'm in a similar boat, except I have 3.6kWp of solar too. I currently have an application in to install a Tesla PW3 and additional 3.6kWp of solar, but am doubtful it will be granted by the DNO.
Like you, I'm on the Octopus Cosy tariff, and estimate that the 13.5kWh capacity of the PW3 would see me through the 6 hour periods between cheap rate slots in winter, and in summer the battery capacity will cover a full day on a single charge.
Financially, the numbers do not stack up for the battery alone, but there are other considerations for us such as comfort and use (as we currently switch off during peak rates), and the green / grid independence aspects of eliminating our draw on the grid at peak times.
I take @transparent's view that it's difficult to price something when there is no certainty over pricing or tariffs in 12 months time, let alone over the 10 years plus life of a battery. For me, adding as much solar and battery as possible, at a price I'm comfortable with, means we maximise our resilience to absorb any future pricing changes down the line.
On a slightly different note, @transparent and I had taken a look at my local infrastructure (substation etc) and concluded I was unlikely to receive a favourable DNO offer. I've done a little more research whilst I await the DNO responses. My limited understanding is that the DNO is responsible for keeping mains voltage at 230v+/-10% (so 252v max). Crudely, electricity flows from high voltage to low voltage, so when your inverter wants to export electricity, it increases the voltage to allow that export which has an effect on the local voltage, which the DNO must keep below 252v. I've been monitoring the voltage in my house over the last couple days, and it varies between around 243v and 249v. It's currently sat at around 248v at midday whilst the sun is out and we are exporting. Given it's already high and pretty close to the maximum permitted 252v, I understand @transparent view that we are unlikely to receive a favourable offer, so our PW3 + additional solar plans may be academic anyway.
I would like, and can afford, to get a battery. But I cant, however hard I try, make the business case pay (and I dont see an environmental case, at least not yet). So at present I am tarrif surfing in the hope that battery prices will come down by the 30% thats needed to make it pay. I have an EV, a heat pump and 4kWp of solar.
Er James, lol.... I wrote about 'why' with my explanation of Demand-side Flexibility - a battery let's you escape the surge pricing that will inevitably become part of electricity pricing. 😁
And I mean 'inevitably'. [see below]
Meanwhile, I'm fascinated by the ROI approach to these things because we don't really know the economics which rely on too much futurology. I understand it more for those who can just-about-scrape the funds although the same futurology problem applies.
However the landscape of energy appears right now is not how it will appear in the coming years. There's huge shake-ups on the horizon. Which is precisely why I am working on it. 🫣
I would like, and can afford, to get a battery. But I cant, however hard I try, make the business case pay (and I dont see an environmental case, at least not yet). So at present I am tarrif surfing in the hope that battery prices will come down by the 30% thats needed to make it pay. I have an EV, a heat pump and 4kWp of solar.
Er James, lol.... I wrote about 'why' with my explanation of Demand-side Flexibility - a battery let's you escape the surge pricing that will inevitably become part of electricity pricing. 😁
And I mean 'inevitably'. [see below]
Meanwhile, I'm fascinated by the ROI approach to these things because we don't really know the economics which rely on too much futurology. I understand it more for those who can just-about-scrape the funds although the same futurology problem applies.
However the landscape of energy appears right now is not how it will appear in the coming years. There's huge shake-ups on the horizon. Which is precisely why I am working on it. 🫣
Exactly, and as in my case above, we may have left it too late as our neighbours have sucked up all the local capacity leaving us with just the standard 3.68kW allowable DNO offer.
By the time batteries are 'affordable' on a ROI basis, the same may apply for many others and people find themselves unable to get the required DNO permissions to install them.
Interestingly, we had a similar situation with fibre broadband (FTTC) in our village, whereby the local cabinet served copper connections to 512 properties, but only had space for up to 128 fibre connections, so it was first come, first served and everyone else after the first 128 properties were told no. So this issue does not just affect the energy infrastructure industry.
This post was modified 5 hours ago 2 times by Old_Scientist
Exactly, and as in my case above, we may have left it too late as our neighbours have sucked up all the local capacity leaving us with just the standard 3.68kW allowable DNO offer.
By the time batteries are affordable, the same may apply for many others and people find themselves unable to get the required DNO permissions to install them.
Thanks
I presume 3.86kW applies to export (is this correct?).
I already have 3.86kW export capacity for the solar, Im guessing they are unlikely to allow me any more anyway
But I confess I hadn't factored into my ROI calculations risk of future blocks on doing things with batteries!
Meanwhile, I'm fascinated by the ROI approach to these things because we don't really know the economics which rely on too much futurology. I understand it more for those who can just-about-scrape the funds although the same futurology problem applies.
Im using a fairly crude approach (attached - but be warned there may be errors!) based on current tariffs and estimated consumption split, but with an allowance
for the cost of capital (ie the interest paid or lost on the capital price of the battery). Most battery manufacturers seem to warranty for 10 or max 15 years so Im looking for at worst break even in
that time. I cant get close at present to break even on typically 5K investment for 10kWh or 7K for 20kWh. bring prices down by 2k on either and Id be there.
My solar inverter is now 14 years old so, assuming I have to replace it sometime soon (they were said to have a lifetime of 10 years), then this would probably come close enough to tipping the balance.
4kW peak of solar PV since 2011; EV and a 1930s house which has been partially renovated to improve its efficiency. 7kW Vaillant heat pump.
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