Which storage battery

benson1980

Hi all,

We have recently had a 12kW ashp installed in our 4 bed house (4 of us); prior to this we were reasonably heavy users anyway using anywhere between 5-15kW. Currently we’re between 15 and 25kW and this will obviously increase in winter.

I have just started to get quotes for battery storage; we also have solar panels (3.76kW) and an old 4kW sunny boy inverter which is around 13 yrs old. This is on the old FIT tariff where assumed export is 50% of what we generate so we need to keep this running. What we mainly want to take advantage of is the tariffs such as cosy, charging up the battery during off peak.

we have had one quote thus far which is for 2x 9.5kW givenergy batteries plus a 5kW inverter- 6.3k. One other company we contacted did both givenergy and power walls and straight away recommended the latter for a house with a ashp, with the ballpark being 7.5k.

Ive read a couple of the posts on here regarding issues with givenergy. That said the quote for 19kW is obviously much cheaper than one 13.5k power wall. Any advice on what might be the better option (or indeed others I should be looking at)

Thanks

Screwdriva

As both solutions do not cover your consumption, it seems to me like you would benefit more from a PowerWall 3 + expansion pack, which will be 27kW of storage. 

The installer should be able to install the expansion pack for ~£5.5K in a couple months (they cost less). GivEnergy’s closest PW3 comparable is the All in One which is getting an update soon to help it compete. Unless £ is the primary factor, my vote goes to the PW3. 

benson1980

Screwdriva said:

As both solutions do not cover your consumption, it seems to me like you would benefit more from a PowerWall 3 + expansion pack, which will be 27kW of storage. 

The installer should be able to install the expansion pack for ~£5.5K in a couple months (they cost less). GivEnergy’s closest PW3 comparable is the All in One which is getting an update soon to help it compete. Unless £ is the primary factor, my vote goes to the PW3. 

Thanks. The expansion packs were mentioned to me today actually by a powerwall installer so as you say that might be an option down the line for us. Appreciate the pointers

Magnitio

Screwdriva said:

As both solutions do not cover your consumption, it seems to me like you would benefit more from a PowerWall 3 + expansion pack, which will be 27kW of storage. 

The installer should be able to install the expansion pack for ~£5.5K in a couple months (they cost less). GivEnergy’s closest PW3 comparable is the All in One which is getting an update soon to help it compete. Unless £ is the primary factor, my vote goes to the PW3. 

Given that a tariff such as Cosy allows charging a battery and maximising your heat-pump usage during 3 periods of the day, then 27kWh of storage is probably excessive and only required on very cold days.

Heedtheadvice

Do consider if you have the space and load bearing capacity for 27kW batteries too.

I am also on FIT ( and still am) but it can be beneficial to move over to SEG for the export side and retain FIT for the generation income. You would need to consider carefully if that is possible/beneficial for you. Easy to stay on deemed export when that export quantity is low but you might end up exporting a lot during good generation periods ( such  summer ) if also filing your batts on the Cosy tariff. Having a big consumption it might pay to consider widely?

There is at least one other poster who is in a similar position using lots of leccy for heating and big batts....

NedS

Magnitio said:

Screwdriva said:

As both solutions do not cover your consumption, it seems to me like you would benefit more from a PowerWall 3 + expansion pack, which will be 27kW of storage. 

The installer should be able to install the expansion pack for ~£5.5K in a couple months (they cost less). GivEnergy’s closest PW3 comparable is the All in One which is getting an update soon to help it compete. Unless £ is the primary factor, my vote goes to the PW3. 

Given that a tariff such as Cosy allows charging a battery and maximising your heat-pump usage during 3 periods of the day, then 27kWh of storage is probably excessive and only required on very cold days.

That was my thinking too - the 3 cheap slots on Cosy effectively allow batteries to be cycled 3 times per day, so you could get close to 30kWh per day out of a 10kW battery, plus your actual usage during the 3 cheap Cosy slots when you are pulling directly from the grid, all of which may cover you for 95% of the year.

I'd be interested to hear how people get on with one decent 10-13kW battery cycling 3 times daily in winter.

Screwdriva

Given recent changes in some of the Octopus smart tariff rate cards, I would hesitate to make a recommendation on battery capacity based on the assumption that Cozy will remain as viable for the next 10+ years. 

That said, I would start with just the PW3 and evaluate if the expansion pack makes sense at a later date. 

Reed_Richards

Both your battery and your inverter will have a limit on how much power they can provide.  For example, I have a 48 V battery and my inverter is limited to 50 A (the battery could do more).  This means the maximum power will be 2.4 kW.  That is not enough to power my heat pump for a lot of the time so I have to import electricity to top-up the power even if my battery has plenty of charge left.  So whatever you are thinking of getting, check that it can provide the power output you need.  

ed110220

How about the Frogstar battery? It's 15 kWh and seems to be the best value battery out there.

I'd definitely echo the above, to check what the maximum charge and discharge rate of the inverter is, because it's not always the same as the power from PV. Eg my Growatt SPH5000 inverter can supply up to 5 kW from the solar (and is usually described as a 5 kW inverter) but can only charge and discharge batteries up to 3 kW.

With your ASHP you'll definitely want to be able to charge and discharge at a good rate. Otherwise you'll be importing from the grid even when you have juice in the battery eg if you're using 5 kW but the inverter can only supply 3 kW, the extra 2 kW will come from the grid even if your battery is full. Also, if the charge rate isn't high enough you may not be able to charge up as much as you need during the lower price period, eg Octopus Flux is cheapest for the three hours from 02:00 so at 3 kW charging that is a maximum of 9 kWh you can soak up at the cheap rate. 

ludditeJazz

I wonder if I might jump on here for advice? My winter battery demand is rarely over 12kWh (after accounting for solar generation), SoEnergy are offering a 10kw battery plus fitting for £5.2k which sounds reasonable. Should I be considering alternatives, and will these include installation, wiring into my solar and flex to specify how much power I want to draw and store at night? (I’m currently favouring Octopus Intelligent Go - they tell me I can use home battery in place of EV). Many thanks for any tips.

Solar install 2016, 2.4kW array (actual performance), S facing roof, Inverter (details to follow) 

QrizB

ludditeJazz said:

I wonder if I might jump on here for advice? My winter battery demand is rarely over 12kWh (after accounting for solar generation), SoEnergy are offering a 10kw battery plus fitting for £5.2k which sounds reasonable.

The price is in the right ballpark.

Is that an AC-coupled battery, which will leave your existing solar PV alone and shouldn't affect your FIT payments (assuming you get them), or are they proposing a hybrid inverter and a DC-coupled battery?

Do you know which battery equipment they're offering? There are various brands and models and some seem more reliable than others.