Growatt Battery Storage — Bulb Community

Growatt Battery Storage

Good Evening All,

I bought a second hand Growatt SP2000 and 5kWHr battery pack off a well known internet site last July but ran out of time to install it prior to heading back to work at sea.

At the same time I bought a number of 235W solar PV panels and an Aurora PVI 3.6 inverter.

I've yet to properly mount the PV panels on the outbuilding roof so they're currently propped up against a SSW facing wall.

I've been struggling to get the system working and, with the kind assistance of a Growatt engineer (in fairness they don't have to spend time dealing with unofficial purchases), I now have a working system.

The Growatt re-directs any exported electricity over 100W to charging the battery pack. Once the battery is full all the solar PV electricity will then be exported.

Later in the day as the solar PV tails off and the house starts importing electricity the battery pack will start discharging.

Now to sit back whilst doing a bit more to save the planet.

Anybody else out there with battery storage systems?




  • Wow @linesrg that sounds like a really impressive setup! Hopefully you'll give the rest of the country some ideas...
  • linesrg said:

    Anybody else out there with battery storage systems?

    I wish! Maybe I'll get one at the same time as I get my electric car...
  • Good Afternoon All,

    It's difficult to know whether domestic battery storage is an ideal solution. With electrical generation/ storage there are very obvious gains by doing things on a large industrial scale.

    Installing any one of what appears to be an increasing number of domestic battery storage options with 5% VAT applied seems to be an expanding market.

    A big argument/ sales pitch is harnessing any excess energy produced on site rather than exporting it. The current stumbling block is that the installs are too expensive mainly due to the cost of lithium batteries (there is at least one option allowing lead acid batteries), this situation will continue to improve.

    If your are gaining from FIT payments for the solar energy produced in the first place and then importing energy in the mid to late evening you are gaining both from the FIT payment and what you save from saved imported electricity as the battery discharges.


  • edited May 5
    Presumably you don't enjoy FiT as your diy installation will not be MCS, hence all you will save is the import cost of energy at the Tarrif applicable to the time of use.

    I like the idea of (free) pv charged battery packs, but the economics just don't stack up. In your case, with a 5kWh battery - assuming that you get one cycle per day and use the stored capacity at a 15p/kW Tarrif time period, you have saved the (drum roll)..... sum of 75p! Extrapolate that to a years use and you may have saved circa £270.

    Most lithium battery packs are warranted for circa 6-8 years (with incrementally diminishing capacity), so let's say 7-years life x £270 = £1,890 potential savings. Compared to the purchase price of the Growatt charger+battery @ £2,990. Add the cost of AC and DC isolators etc and the total battery set up could cost easily twice as much as you could realistically save.

    I appreciate that you bought your set up second hand so almost certainly paid substantially less than the retail price, but given the reduced capacity from a used battery (I.e. you won't get 5kWh) I'd guess that you will still struggle to get much of a financial benefit over the life of the battery system.

    I originally looked at purchasing a Tesla PW2, touted as being 13.4kWh capacity, but although Tesla warrant the PW2 for 10-yrs, it is only for 80% capacity. So, averaging the 20% loss over the warranty period means an adjusted capacity of 13.1kWh, then factor in the software limited 80% DoD (depth of discharge) and you end up with circa 10kWh real world capacity.

    So, using the same rationale as per the Growatt, this gives us £1.50/day saved or £390/yr x 10yrs verses an installed cost >£6k .... the sums just don't add up over the life of the battery pack.

    The final nail in the coffin is that it will be a rare day indeed where a FiT eligible, <4kW pv installation in the UK is going to produce enough surplus energy to recharge a fully discharged PW2 battery, hence owners will inevitably resort to topping up with off peak grid supplies, further eroding any financial justification for having a battery pack.
  • edited May 7
    @Edward_S - You are quite right there is no outright economic justification for the route I have followed in the short term. It doesn't qualify for any FIT's payments and is in something of a grey area viz a viz MCS criteria. Having bought everything second hand it does bring the price down.

    As a fellow renewable energy enthusiast pointed out when his system was challenged economically. He argues that taking the long view his system will net him some £50,000 in earnings and savings on imported electricity. His initial install was the earliest rate (currently paying £0.5275 per kW for 25years) and his second install was for a 20 year FIT payment period. I can imagine people using electricity and not getting FIT payments could get aggrieved at having to foot the bill for these payments and, to a degree, understandably so.

    As I have previously stated here and elsewhere I am 'green' by inclination but not suicidally so as far as the financial side goes. Like my colleague mentioned above I will make a substantial profit on my Solar PV system. My heat pump/ Solar ET system will also make a profit.

    If the Growatt simply breaks even then I'll be happy. I can see why people who have invested in Growatts are putting them up for sale. They impact on FIT's payments and will never be 100% efficient. There is a definite downside to DC based battery storage. If you have the ability and can be bothered you can 'manage' deterioration in lithium battery packs by identifying those 'banks' with low voltages and charging accordingly.

    I have a 'spare' Growatt SP2000 and still considering buying a second battery pack (as spares).

    My biggest issue is the inflexibility of SSE to system expansions.

    One thing I forgot to mention is that you ca also get clever about where you get your electricity. Ebico Night Owl for instance would allow you to do some charging at night relatively cheaper than with Bulb but there is a limit to this as per their T&C's.

    Litium ion battery prices are dropping rapidly and things considered not economic even a year ago have a completely different view now.

    I was looking at getting an SP3000 controller but was put off by:-

    a) the initial purchase price (I have yet to see one of these come up on that well know auction site) and
    b) the need to fit a bi-directional meter -

    This would allow night time charging of the battery packs but is an expensive solution. The Tesla Powerwall has such a feature included of course.

    The fact remains that even with a 5% VAT rate applied they still don't make sense as a new, installer installed solution.


  • Can any UK installs of whole house battery devices be used as whole house UPS units in case of a grid power failure?

    I seem to remember a discussion when the original Powerwalls came out saying that it wasn't permitted here due to the possibility of zapping engineers working on fixing the fault. There seems to be plenty of discussion about the functionality in other countries but I'm struggling to find anything relevant over here.
  • edited May 10
    You guys know a lot more about this than me, but we got a 4.5kw system installed last year and at the same time we got this installed...

    What it does is route any excess energy to the immersion heater and then heats the water tank too. It's brilliant - last year we had the boiler switched off from April to October so our gas usage was almost zero and it means that we're using almost 90% of the solar power generated, but getting paid 50% when we're only actually exporting 10%.

    We did look into getting a battery, but we didn't think the numbers worked out either. That Solic 200 only cost £400 to buy and get installed though!
  • @mowcius - I’ll need to do some looking up as I thought Powerwall2 could do this. As I’m sure you are aware it isn’t difficult to achieve from a technical point of view but gaining legislative agreement is a completely different kettle of fish.

    @LesleyG - I’ve got an Immersun unit which does the same job. It powers an ‘immersion’ heater in my External Heat Store (EHS). This is also heated by the Solar Evacuated Tube (ET) system. In the height of summer I’m dumping heat......


  • The Tesla PW2 is touted as having the capability to provide an off grid supply in event of grid failure 'sometime in the future'...

    ...I believe that you can future proof new PW2 purchases by buying a modified gateway unit (+£600) and having it installed concurrently. But, Tesla have yet to obtain the necessary permissions/certification so it could be a wasted £600.

    Where I live we are blighted by fairly regular brown outs and short duration grid interruptions (too many new houses being built and infrastructure on its knees due to a failure to upgrade capacity), but frankly the freezer & fridge manage to stay cold over the typical 1-2hrs service interruption, in our household there is more upset at failed recordings of GoT ;)

    This was one of my main drivers to originally look at the PW2, but Tesla have been touting this 'feature' as coming for more than a year now....
  • edited May 14
    Edward_S said:

    Where I live we are blighted by fairly regular brown outs and short duration grid interruptions (too many new houses being built and infrastructure on its knees due to a failure to upgrade capacity), but frankly the freezer & fridge manage to stay cold over the typical 1-2hrs service interruption, in our household there is more upset at failed recordings of GoT ;)

    This was one of my main drivers to originally look at the PW2, but Tesla have been touting this 'feature' as coming for more than a year now....

    Thankfully the power is pretty good around here but even so, I've had my routers and storage server on a UPS for a couple of years now.
    There have been a few brownouts and a couple of complete drops in that time caused by the grid, and a couple caused by me (plus a faulty toaster last week) :mrgreen:

    I only get about 15 minutes on the setup that I have, but it's been enough so far. 1-2 hours is insane though. I hope you're being reimbursed for the inconvenience!
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