Solar Together and retrofit batteries

70sbudgie

Solar Together has finally come to Cheshire and I signed up to see what was being offered for retrofit batteries.

As the design is based on very basic questions, the first step is to work out whether the design is right for me (step 2 is the price). I have been offered 3kWh, 6kWh, 9kWh or 12.1kWh Growatt batteries & inverter with a recommendation of 6kWh based on what I said my PV generation and import currently is. By a national installer that I've not previously heard of.

Batteries would be just one more move towards the holy grail of energy independence, with a heat pump somewhere in the future. I know that PV, batteries and heat pump is meant to be the magic 3 retrofit technologies, but is it possible to size a battery to support a heat pump? Given that during the winter, the battery charge period could be only 3 hours of super cheap rate and a heat pump could be 7kW or 12kW? So far I've only seen battery inverters with max 3kW discharge (though I appreciate I haven't yet made much headway with my research).

Any thoughts / tips on where to direct my research would be much appreciated.

Reed_Richards

I have PV, a battery and a heat pump but am by no means energy independent.  I have a 12 kW heat pump for central heating and hot water.  Between Jan 5th and 6th this year it consumed 43.32 kWh of electricity.  Here is a chart for most of Jan 23

 So what you need is an electric car with a 40 or 50 kWh battery, V2H capability and not actually wanting to drive your car very much in winter so it can spend most of its time hooked-up to your V2H car charger.  One day, maybe?  And that's not energy independence, that's running everything on cheaper electricity.

70sbudgie

Thank you. I appreciate that energy independence and running everything cheaply on electricity are not the same thing. But if it is possible to achieve the latter without compromising on comfort too much, then I think the former is a step in the process. (I agree about the large EV sized battery and that had originally been my plan, but V2H hasn't developed as much as I thought it would when I installed the PV, so I'm now considering alternatives).

Do you mind me asking what size your PV and batteries are? And do you charge your batteries during a cheap rate to support the HP? Even if it clearly doesn't cover all its input.

Reed_Richards

I got an EV about a month ago and on the same day moved to E.on Next's EV tariff which gives me midnight to 07:00 at 9.5p per kWh.  I only managed to get a smart meter installed in August (after an earlier failed attempt) and before that I could not access any time-of-use tariff.  I have a 6.5 kWh battery that I charge to 100% overnight then run down to 10% during the day.  I have 12 x 400 W solar panels, so 4.8 kW peak total.  With hindsight, I should have got a few more.

1961Nick

At this time of year I can just about heat the house with our air/air heat pumps. Total combined maximum output is 9kWh with average daily consumption running at around 12kWh. Our 19.2kWh battery will just about get us through the 18 hour peak period most days unless it's a heavy laundry day. The SCOPs are over 5 which is a lot better than you'd get on an air/water heat pump.

As suggested earlier, you'd really need V2H & a vehicle with at least a 40kWh battery to stand a chance of making a heat pump work entirely on off-peak electricity. Additionally, a domestic battery would also be required for when the vehicle is off site.

70sbudgie

Reed_Richards said:

I got an EV about a month ago and on the same day moved to E.on Next's EV tariff which gives me midnight to 07:00 at 9.5p per kWh.  I only managed to get a smart meter installed in August (after an earlier failed attempt) and before that I could not access any time-of-use tariff.  I have a 6.5 kWh battery that I charge to 100% overnight then run down to 10% during the day.  I have 12 x 400 W solar panels, so 4.8 kW peak total.  With hindsight, I should have got a few more.

How far through the day does your 90% discharge get you? Past the expensive 3 hours? 

Thank you both for your comments. 

I'd like to think that a V2H EV is still a future option, even if it is a bit further in the future than I'd initially hoped. 

So based on the above, I am now thinking it probably isn't worth oversizing the batteries too much as the 12kWhr wouldn't make enough of an impression on a heat pump use to justify the upfront expenditure.

9kWhr with a charge / discharge rate of 2.5kW, would give me about 3 hours to charge from 15% to 100% (and vice versa at full output). And probably give me a full day's use at my current usage (~7.5kWhrs excluding EV charging, which would also be in the 3 hour window). 

However, I will be looking for expandability in the specs. 

Reed_Richards

I don't have an expensive 3 hours; you're possibly thinking of some fancy Octopus tariff but at the moment getting a full 7 hours of cheap electricity suits me best.  Today there was minimal sun to top-up my battery and this had fallen to its minimum 10% charge by about 14:15 (and it was approximately 10 C outside). 

70sbudgie

Thank you for the comments above.

I'm still not sure if the design is right for me, but I guess I might have to compromise somewhere - either design or cost.

So I would appreciate some advice on the cost of retrofit battery installations, if possible.

The Solar Together quote is offering a 3kW (AC nominal power) Growatt inverter with 3x 3.3kWhr Growatt batteries for £7,020 (Inc VAT).

I have been able to get a standard quote from the my energi website for a 5kW inverter with 2x5kWhr batteries for £11,102 (Inc VAT). (The smaller inverter is less than £100 cheaper). (I haven't been able to find anything that indicates the charge / discharge power for the Libbi is different to the headline figure)

Are you able to advise on the relative qualities of the two manufacturers and whether the Solar Together quote is reasonable for current prices? The installer is called Grant Store - does anyone know / have experience of this installer?

1961Nick

70sbudgie said:

Thank you for the comments above.

I'm still not sure if the design is right for me, but I guess I might have to compromise somewhere - either design or cost.

So I would appreciate some advice on the cost of retrofit battery installations, if possible.

The Solar Together quote is offering a 3kW (AC nominal power) Growatt inverter with 3x 3.3kWhr Growatt batteries for £7,020 (Inc VAT).

I have been able to get a standard quote from the my energi website for a 5kW inverter with 2x5kWhr batteries for £11,102 (Inc VAT). (The smaller inverter is less than £100 cheaper). (I haven't been able to find anything that indicates the charge / discharge power for the Libbi is different to the headline figure)

Are you able to advise on the relative qualities of the two manufacturers and whether the Solar Together quote is reasonable for current prices? The installer is called Grant Store - does anyone know / have experience of this installer?

For a 10kWh AC coupled HESS you should be looking at £5000 - £7000. If you pay excessively over that amount the ROI will be well over 10 years. Here's an example of what's available for £7K (not a recommendation btw)...

https://www.pluginsolar.co.uk/?product=givenergy-all-in-one-6kw-ac-charger-and-13-5kwh-battery-with-100-dod-with-gateway-for-eps-backup

70sbudgie

1961Nick said:

70sbudgie said:

Thank you for the comments above.

I'm still not sure if the design is right for me, but I guess I might have to compromise somewhere - either design or cost.

So I would appreciate some advice on the cost of retrofit battery installations, if possible.

The Solar Together quote is offering a 3kW (AC nominal power) Growatt inverter with 3x 3.3kWhr Growatt batteries for £7,020 (Inc VAT).

I have been able to get a standard quote from the my energi website for a 5kW inverter with 2x5kWhr batteries for £11,102 (Inc VAT). (The smaller inverter is less than £100 cheaper). (I haven't been able to find anything that indicates the charge / discharge power for the Libbi is different to the headline figure)

Are you able to advise on the relative qualities of the two manufacturers and whether the Solar Together quote is reasonable for current prices? The installer is called Grant Store - does anyone know / have experience of this installer?

For a 10kWh AC coupled HESS you should be looking at £5000 - £7000. If you pay excessively over that amount the ROI will be well over 10 years. Here's an example of what's available for £7K (not a recommendation btw)...

https://www.pluginsolar.co.uk/?product=givenergy-all-in-one-6kw-ac-charger-and-13-5kwh-battery-with-100-dod-with-gateway-for-eps-backup

Thanks.

What sort of installation costs would you expect with that GivEnergy set up? Both my quotes above include installation and VAT (the GivEnergy appears to exclude installation). So GivEnergy could potentially be on par with the My Energi quote, though it has a much larger capacity than the GroWatt I've been offered and is more expensive. 

Netexporter

70sbudgie said:

1961Nick said:

70sbudgie said:

Thank you for the comments above.

I'm still not sure if the design is right for me, but I guess I might have to compromise somewhere - either design or cost.

So I would appreciate some advice on the cost of retrofit battery installations, if possible.

The Solar Together quote is offering a 3kW (AC nominal power) Growatt inverter with 3x 3.3kWhr Growatt batteries for £7,020 (Inc VAT).

I have been able to get a standard quote from the my energi website for a 5kW inverter with 2x5kWhr batteries for £11,102 (Inc VAT). (The smaller inverter is less than £100 cheaper). (I haven't been able to find anything that indicates the charge / discharge power for the Libbi is different to the headline figure)

Are you able to advise on the relative qualities of the two manufacturers and whether the Solar Together quote is reasonable for current prices? The installer is called Grant Store - does anyone know / have experience of this installer?

For a 10kWh AC coupled HESS you should be looking at £5000 - £7000. If you pay excessively over that amount the ROI will be well over 10 years. Here's an example of what's available for £7K (not a recommendation btw)...

https://www.pluginsolar.co.uk/?product=givenergy-all-in-one-6kw-ac-charger-and-13-5kwh-battery-with-100-dod-with-gateway-for-eps-backup

Thanks.

What sort of installation costs would you expect with that GivEnergy set up? Both my quotes above include installation and VAT (the GivEnergy appears to exclude installation). So GivEnergy could potentially be on par with the My Energi quote, though it has a much larger capacity than the GroWatt I've been offered and is more expensive. 

I've seen quotes of £8000 to supply and fit a Givenergy AiO and gateway.

It's the battery I'm intending to fit. Tesla Powerwall specification but far less expensive, more availability and, most importantly, no Elon Musk.