@jamespa jumping on this thread late, and I'm of a similar opinion to you, I've been getting quotes every few years for a battery.

The payback has gone from none whatsoever, to marginal.  Prices have stayed fairly static, while capacity (including depth of discharge), power, warranty and safety have improved, so better value overall.

I'm hopeful that the newer Sodium Ion chemistry launched by BYD for their small affordable domestic car market may soon find it's way into stationery battery storage.

In theory that could mark the point at which home batteries become really affordable, even safer, and work in the cold without heaters etc. 🤞 

Posted by: @scalextrix

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@jamespa jumping on this thread late, and I'm of a similar opinion to you, I've been getting quotes every few years for a battery.

The payback has gone from none whatsoever, to marginal.  Prices have stayed fairly static, while capacity (including depth of discharge), power, warranty and safety have improved, so better value overall.

I'm hopeful that the newer Sodium Ion chemistry launched by BYD for their small affordable domestic car market may soon find it's way into stationery battery storage.

In theory that could mark the point at which home batteries become really affordable, even safer, and work in the cold without heaters etc. 🤞 

Im also hopeful that prices will come down but it does seem very slow.  Im currently getting a quote once more, but its still working out at £400-500/kWh installed, which is still too much once you account for loss of interest on the capital, and tax on the revenue from arbitrage (sorry but I don't like building a business case on an assumption of tax avoidance)

Im also hopeful that bi directional EV chargers will return to the market, so I can replace our second car, a petrol Fiesta which spends almost all of its life on the driveway, with an aging Nissan Leaf that then doubles as a massive home storage battery.

Finally there is another revenue stream which Capture Energy are beginning to tout and Octopus will surely offer.  If you can guarantee availability to either consume or produce 1MW or above, you can be paid an availability fee by the grid for flexibility, and a further fee if that flexibility is actually used.  Individuals obviously cant do this, but 'virtual power companies' can, by aggregating many consumer sources.  Sharing the revenue from this with the virtual power company provides an additional income stream which has the potential to help with the business case.

its very interesting times for sure

Posted by: @scalextrix

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I'm hopeful that the newer Sodium Ion chemistry launched by BYD for their small affordable domestic car market may soon find it's way into stationery battery storage.

I would be surprised if the battery chemistry is going to be a major factor in your viability assessment.

The major costs are

• installation time, incl tooling
• the inverter(s), cabling, safety trips etc
• training, certification, insurance & warranties

Let's combine this observation with the next comment from James:

Posted by: @jamespa

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revenue stream which Capture Energy are beginning to tout and Octopus will surely offer.  If you can guarantee availability to either consume or produce 1MW or above, you can be paid an availability fee by the grid for flexibility

This is therefore an attractive path to be taken by local Community Energy groups.

The RIIO-ED2 Agreements between DNOs and Ofgem all have variations, but they do contain financial incentives for DNOs to

• engage with, and provide support to Community Energy initiatives
• offer flexibility-services

But DNOs may not own or control generation or storage assets.

They would, however, be 'interested' in Community Groups who could get their act together and do their own low-cost (semi-DIY) battery installations.
The more widespread were those storage batteries, the greater flexibility could be 'offered' back to that DNO.

The three key issues they're interested in are:

1. absorbing excess-generation from renewable generation sites in the area (typically connected at 11kV or 33kV)
2. time-slicing use of the (extensive) 11kV network so as to better use its available capacity over each day/night
3. varying the charge current being taken from the grid such that losses due to phase-imbalance are progressively reduced

OK... so that requires a bit of grid monitoring, but not as much as you might suppose.

If I have LV monitors on several different 11kV (rural) feeds from a Primary Substation, I can detect which fluctuations are constrained to each feed,
and which are due to effects at the area-wide 33kV level:

Ignore the red & purple traces - they're being manually controlled.

The voltage rises/falls between 00:30 and 03:30 are area-wide because they affect Brown, Grey and Peach locations equally.

In contrast, the sudden dip detected at 16:15 by the grey monitor is peculiar to that Feed.

So why don't we see this approach being implemented across multiple community-installed storage batteries to offer flexibility services?

1. there's no revenue stream which could be harnessed to make a profit for anyone
2. there's no Nodal-Tariffs available to pay the storage battery owners
3. DESNZ seem to think that Zonal-Tariffs would operate according to political boundaries, irrespective of how the grid actually works
4. the Secretary of State for ESNZ has twice changed his mind on introducing sub-national tariff structures in the first half of 2025, partly under pressure from No.10
5. there's no Innovation Funding available for developing solutions based on 'concepts'; there must be a 'product' which can be assessed for commercial viability
6. if we don't implement flexibility-services using distributed mass-storage, then grid infrastructure requires massive upgrades... which equates to long-term profits for DNOs

I can cope with the technological parts of the conundrum...
... it's the politics and shareholders' profits which frustrate me!