Hi. You would probably need to swap the inverter for a hybrid inverter. That would support battery charging. However I would look into the cost v payback time as many have come to the conclusion that it just doesn’t make financial sense at the moment. 

If you have a decent export tariff such as Octopus’s 15p then you use the export to build up your cash in your account over the summer and then spend it in winter. 
Broad brush guess on price for a reasonable sized battery and its inverter is a few thousand, you may also need some panels re-wired (less likely) which would be scaffolding which is about £1k.

The best size of battery is to cover your use for an average day or the size to last about 6hours on your worst case use rate. There’s a lots more to be said on this but that’s my rough conclusion after playing with excel on our usage for ages.

In doing a  payback your potential battery would only last for the same day. We at present are generating 30kWh each day, the heat pump (and the house) use 16-20kWh so there’s lots to export. Think of it as a seasonal sized battery!

Octopus would give you an on line estimate for a battery and then their sales team will pester you and you’ll get the timing. But the payback time maybe above 15years.

@judith that’s interesting as my calculations suggested a smaller battery that didn’t last the day was more cost effective for me. I couldn’t even make the case for an extra module given I already had the inverter and battery management system. 

As you say a 15 year payback time seems about right but will the battery last that long? Mine has a 10 year warranty. 

15 years? crikey!  I'm age 65 so that will definatley not be worth it.  Thanks for the info. 🙂

wouldn't post despite clicking over and over, then posted multiple. Sorry. Isn't letting me delete the extras.  Feel free to tidy my mess lol

... 🙂

.... 🙂

Posted by: @ellyse

↑

15 years? crikey!  I'm age 65 so that will definatley not be worth it.  Thanks for the info. 🙂

That’s just a guess, and your usage patterns may vary. It might be worth trying to work it out for your circumstances.

If you want to improve your comfort (and possibly your bills) then better control might be the best route forward. I don’t know personally where to start with an Ecodan.

@ellyse i was 63 when I had my PV and Battery setup, prices of batteries are continuing to fall. Get a quote and do the maths.

If you assume a standard tariff around 24p/kWh then it would take over 10 years for payback, but get on the Octopus Cosy tariff with 8h half price per day, use that to charge the battery and power the house on the battery/PV during the expensive periods and the cost savings mount up; my pay back estimate is now 8 years. When prices double, you will save even more money as PV generated power saves you double too, so payback is quicker 🙂

@agentgeorge I have just transferred to Intelligent Octopus Flux from April 1st. and I hope this does not prove to be a foolish move!

Cosy was my tariff of choice from July 1st. 2024 and will probably be my choice again come heat pump season about Oct. / Nov. Having 27 kWh of powerwall capacity, 8 tentacles takes approx. 80% of this plus my excess solar between 16:00 and 19:00 each day and pays me ~30 pence per kWh for it all. (at other times, any solar export is at ~23 pence. per kWh) At the moment the intelligent Kraken kit partially / fully charges my Powerwall again at night at the lower rate of ~23 pence. per kWh. I just hope the arbitrage exceeds the battery wear! Regards, Toodles.

Posted by: @agentgeorge

↑

i was 63 when I had my PV and Battery setup, prices of batteries are continuing to fall. Get a quote and do the maths.

The difficulty with this discussion is that it's referring to tariffs which are presently available,
then using that information to calculate the Return on Investment for a battery, operating within regulatory controls which haven't yet been proposed.

The assessment needs to be made against the nature of the grid which is likely to exist at least 5-years hence
... after we've passed the time frame for decarbonisation of electricity generation.

2: Adding a case and electronics to a set of batteries more than doubles the cost.

The price of the raw lithium cells is indeed falling rapidly,
But it's not being well reflected in the cost of buying in a battery in a nice-looking enclosure.

The assembly costs for placing cells into a case are roughly the same, whatever the size/capacity of the battery.
Thus smaller batteries have a higher price per kWh of storage capacity.

3: On-site installation costs are rising.

National Insurance, annual certification fees, tooling and transport are weighing heavily on those electricians who install inverters and batteries.
They need to complete more installations per year in order to cover those additional costs.

So their quotations are progressively biassed in favour of those products which can be installed fastest.

Unfortunately the storage batteries and inverters which can be installed quickly are often those which 'lock in' the consumer to a particular manufacturer, and product range.

Even those who wisely bought battery & inverter combinations from the British company, GivEnergy, just a couple of years ago,
are now discovering that the 2025 range of 'high-voltage' batteries and 'All-in-One' packages are incompatible with their existing systems.