Home Storage Battery

[Mihir]

Personally, I wouldn't have batteries in the loft the temp extremes aren't good for the battery chemistry no matter what it says on the label. I had my first PV system installed in 2011 and had an SMA 4 kW inverter in my large very spacious loft and it struggled in the summer and it ramped down of output in summer as the loft temp went up was the limiting factor in solar generation. Had I installed the inverter in my garage I would have lost 1% to 1.5% in DC Volt drop for sure but the inverter wouldn't have been throttling back and losing 10% to 15% output. I'm looking at a new system now (I moved 3 years ago) and the DC runs would be longer this time than at my previous house and I'm seeing spec sheets for inverters that say 0C to +60C but then saying throttling from +45C and summer temp's are often above that in my loft. As for batteries, they are really fan cooled as the majority of inverters would be and rely on passive cooling. They generate heat don't forget when charging and discharging and Lithium (found in both LEP and Lion batteries) doesn't like heat but also doesn't like the cold either. The ideal temp for batteries is 25C to 35C in most cases. Pylontech for instance has reduced charge and discharge rates below 8C-10C and can't deliver the specified 1.2 kW whereas the Uhome battery (used by LuxPower) has the advantage over Pylontech in that it can deliver down to 0C.

Tesla Powerwall says it has an operation range down to -20C but what they don't explain is that for the Lion cells to deliver that they need to be heated just as you might precondition your EV battery before a charge in winter or if you want to get full power when driving.

All of this makes a garage if you have one the better place to install battery storage or PV Inverter. I used to sell, survey and design PV systems and I know I made a mistake in my early days in the industry in putting my inverter in the loft but I soon gathered the evidence that this was a mistake. The companies I worked for liked putting inverters in the loft as it was easier to route a single AC 240v armoured cable from loft space, down an outside wall and into the location of the Consumer Unit and meter than to route 2 or 4 individual DC lines. However, the performance and the longevity of the inverter suggests that was not an ideal solution.

Having weighed up the options, I'm pretty certain that I'll be just going with the storage only option this time around and sticking with Octopus Energy. I'm on Go now and when the market stabilises and is a little less crazy I'll switch to Octopus Agile. For the price difference between Solar PV + Storage and just Storage, I could significantly increase the storage to more than I need. Then When Agile starts to have credible plunge pricing I'll switch to that and buy low and export when its peak time and export rates are high.

If you want to be ready for that switch to Octopus Go as there are still very attractive EV nighttime charging rates and it would be great if you used my referral code and share £100 with me (50:50) go to: share.octopus.energy/zappy-guppy-175

Thanks for the amazing explanation @BarryH. Thats a wealth of knowledge from you. I learnt something new today thanks to you!

 

[BarryH]

Thanks for the amazing explanation @Barry. Thats a wealth of knowledge from you. I learnt something new today thanks to you!

One final thing with regards to temperature and an electronic component's life expectancy. Back in the early 1980's when I worked on advanced projects at BT, the labs would need to test components and assemblies to predict life expectancy and Mean Time Between Failure" (MTBF) and this was calculated by accelerating the component aging through temperature stressing ie operating the system at elevated temperature. We were specifying equipment to be deployed in difficult to maintain places and expecting them to operate without attention for 25 years. This is also one of the reasons why there is a difference in the life expectancy of your home internet router and that of a commercial grade or even military grade router. Domestically we'd find it unacceptable to have a fan cooled internet route in the corner and so get dropouts in hot weather and die in 2 years, but in business where these things are in temperature controlled environments and are in equipment racks and are fan cooled, they are more stable and last much longer but also cost more.

 

[AussiePete]

I’ve been documenting what I went through to size and select my solar & battery solution and supplier and have published it at the link below. I’ve tried to keep it relatively simple so that anyone can use the same method to size what they need.

Solar & Battery Install - Where do you start?

solar battery moixa

pghintsandtips.blogspot.com

Hope it helps

 

[Happy Zappy]

Pete, a very useful guide & set of links. Certainly a very good place to start.

Cheers,

David

 

[BarryH]

I’ve been documenting what I went through to size and select my solar & battery solution and supplier and have published it at the link below. I’ve tried to keep it relatively simple so that anyone can use the same method to size what they need.

Solar & Battery Install - Where do you start?

solar battery moixa

pghintsandtips.blogspot.com

Hope it helps

Your comments parallel my own calculations. My usage and baseload are due to circumstances higher than yours Pete. I still think that the cost of Solar per kWh benefited is high compared to the off-peak rate it would replace and in my circumstances, the additional cost of 3.5 kWp of solar is around £3,000 more than the same 8.2 kWh storage (of similar configuration). I calculate that Solar 10 years Warrantee and to be fair Inverter likely to need changing then and I'll probably move house so amortise the £3,000 over 10 years ie £300/year. Solar in the first year is expected to generate 2,700 kWh so that is £300/2,700 = 11.11p/kWh but since PV panels have degradation over time plus get contaminated further reducing their output you should expect over a 10% drop in that 10 years. Put that against the cost of pure ESS (Battery only) and 5p/kWh on Octopus Go solar looks pricy. However, Octopus Go for new contracts is already up to 7.5p from the 5p I got in Dec 2021 so within the next two it will I guess be more expensive than Solar installed today.

On the VAT point, it is worth knowing that if the household bill payer is over 60 in England then the VAT on Battery only ESS is 5%, not 20%, but installers won't necessarily go out of their way to tell you as they have to pay 20% on the kit then claim it back quarterly which hits their cash flow. So since Tesla Powerwall 2 and Tesla Gateway 2 installed is less than £10k and provides 13.5 kWh usable (ie over 10 years 7.4p / kWh storage and less than Solar's 11p) and has an arrangement with Octopus to provide Tesla Power whereby you Charge it at night on Octopus' lowest rates and can export surplus during peak times at a fixed higher rate to help the grid meet demand it can be a cost-effective solution and if you move home you can take the whole thing with you.

 

[AussiePete]

Your comments parallel my own calculations. My usage and baseload are due to circumstances higher than yours Pete. I still think that the cost of Solar per kWh benefited is high compared to the off-peak rate it would replace and in my circumstances, the additional cost of 3.5 kWp of solar is around £3,000 more than the same 8.2 kWh storage (of similar configuration). I calculate that Solar 10 years Warrantee and to be fair Inverter likely to need changing then and I'll probably move house so amortise the £3,000 over 10 years ie £300/year. Solar in the first year is expected to generate 2,700 kWh so that is £300/2,700 = 11.11p/kWh but since PV panels have degradation over time plus get contaminated further reducing their output you should expect over a 10% drop in that 10 years. Put that against the cost of pure ESS (Battery only) and 5p/kWh on Octopus Go solar looks pricy. However, Octopus Go for new contracts is already up to 7.5p from the 5p I got in Dec 2021 so within the next two it will I guess be more expensive than Solar installed today.

On the VAT point, it is worth knowing that if the household bill payer is over 60 in England then the VAT on Battery only ESS is 5%, not 20%, but installers won't necessarily go out of their way to tell you as they have to pay 20% on the kit then claim it back quarterly which hits their cash flow. So since Tesla Powerwall 2 and Tesla Gateway 2 installed is less than £10k and provides 13.5 kWh usable (ie over 10 years 7.4p / kWh storage and less than Solar's 11p) and has an arrangement with Octopus to provide Tesla Power whereby you Charge it at night on Octopus' lowest rates and can export surplus during peak times at a fixed higher rate to help the grid meet demand it can be a cost-effective solution and if you move home you can take the whole thing with you.

Thanks for the feedback. As the blog says I did look at battery only, charging off-peak and using during peak. I worked out quite a saving just doing that. In terms of warranty, solar has a 25year warranty and whilst the inverter and battery only have a 10 year warranty, Moixa extends that for as long as you are a member of Gridseve.

In terms of taking it with you, I have discounted that for 2 reasons

• technologies will have likely moved on so I’d leave the old and install the new
• adding these to my property will increase its value, possibly by more than the cost of the kit itself - especially if I can show how the house is mostly powered by renewables and off-peak (the green incentive) and that has a direct saving in cost of running the house (the wallet incentive)

 

[Gadget Geek]

Your comments parallel my own calculations. My usage and baseload are due to circumstances higher than yours Pete. I still think that the cost of Solar per kWh benefited is high compared to the off-peak rate it would replace and in my circumstances, the additional cost of 3.5 kWp of solar is around £3,000 more than the same 8.2 kWh storage (of similar configuration). I calculate that Solar 10 years Warrantee and to be fair Inverter likely to need changing then and I'll probably move house so amortise the £3,000 over 10 years ie £300/year. Solar in the first year is expected to generate 2,700 kWh so that is £300/2,700 = 11.11p/kWh but since PV panels have degradation over time plus get contaminated further reducing their output you should expect over a 10% drop in that 10 years. Put that against the cost of pure ESS (Battery only) and 5p/kWh on Octopus Go solar looks pricy. However, Octopus Go for new contracts is already up to 7.5p from the 5p I got in Dec 2021 so within the next two it will I guess be more expensive than Solar installed today.

On the VAT point, it is worth knowing that if the household bill payer is over 60 in England then the VAT on Battery only ESS is 5%, not 20%, but installers won't necessarily go out of their way to tell you as they have to pay 20% on the kit then claim it back quarterly which hits their cash flow. So since Tesla Powerwall 2 and Tesla Gateway 2 installed is less than £10k and provides 13.5 kWh usable (ie over 10 years 7.4p / kWh storage and less than Solar's 11p) and has an arrangement with Octopus to provide Tesla Power whereby you Charge it at night on Octopus' lowest rates and can export surplus during peak times at a fixed higher rate to help the grid meet demand it can be a cost-effective solution and if you move home you can take the whole thing with you.

My 4kW PV system is 10 years old and in 2020 generated 4,421.5 kWh over the year (I'm fortunate to live in the south west). I saved £569 in electricity costs. That would be even more in the present financial climate.

On the other hand if you have £5,000 to either buy a system or put in a savings account, the best rate at the moment is 2.2% which would give you £247 over the year.

So I see the solar panels as a long term investment which pays double the dividend than current saving accounts do.

 

[BarryH]

My 4kW PV system is 10 years old and in 2020 generated 4,421.5 kWh over the year (I'm fortunate to live in the south west). I saved £569 in electricity costs. That would be even more in the present financial climate.

On the other hand if you have £5,000 to either buy a system or put in a savings account, the best rate at the moment is 2.2% which would give you £247 over the year.

So I see the solar panels as a long term investment which pays double the dividend than current saving accounts do.

shouldn't that be as you are no doubt on a healthy FIT payment too if you install them circa 2011/2012

 

[Gadget Geek]

shouldn't that be as you are no doubt on a healthy FIT payment too if you install them circa 2011/2012

Yep. The FIT paid off the panels in 4 years.

 

[BarryH]

Yep. The FIT paid off the panels in 4 years.

Yes, I installed a 16-panel high spec system in my last home which took 5 years to breakeven but unfortunately moved a year later

 

[Gadget Geek]

Yes, I installed a 16-panel high spec system in my last home which took 5 years to breakeven but unfortunately moved a year later

Did the panels up the price of the house? Some speculate that it makes a house more desirable.

 

[jdc2022]

Actually with the Vat element, it makes no difference to the fitter if they're charging you vat at 5% or 20%, they'll still reclaim their 20% on purchase (assuming they can) . It's Hmrc who will lose out with the difference.

 

[Harry]

Another non car question.

Does anyone have solar panels and a home storage battery?.

I am thinking of investing 4.5k in a GivEnergy 8kw system linked to solar in order to save on bills.

Does anyone have any experience on if savings are possible and how much bills can be reduced by.

Many thanks.

I do - and if you get one here's a tip. When the battery inverter is set up. ask them to get it to charge at night on economy rate (if you have night rate economy tariff). Then when it discharges in the day you get it back when prices are higher - but even better, the meter thinks it is solar generation so it contributes to any feed in tariff you get (if that still happens..) It is legal and allowed. The battery allows you to store power when you might otherwise feed it to the grid, so even if you don't get FIT payments, you are wasting less of your generation. My typical daily consumption is 8 - 9 kWh, so a battery of around that capacity will allow you to use off peak rates all day. It will definitely pay for itself quite quickly. The GivEnergy 8.2kWh battery is currently on sale for £2437.50. Get your calculator out!

 

[BarryH]

Has anyone LuxPower Hybrid plus Uhome or Pylontech batteries? Or perhaps their Squirrel Pod system?

What's been the experience of LuxPower and Home Energy Group because on Companys House their latest filings showed a weak financial position.

 

[Mihir]

Has anyone LuxPower Hybrid plus Uhome or Pylontech batteries? Or perhaps their Squirrel Pod system?

What's been the experience of LuxPower and Home Energy Group because on Companys House their latest filings showed a weak financial position.

May be this helps @BarryH - Home Storage Battery . Its one of the posts in this same thread. Please do check a few followup posts too.

 

[AussiePete]

Actually with the Vat element, it makes no difference to the fitter if they're charging you vat at 5% or 20%, they'll still reclaim their 20% on purchase (assuming they can) . It's Hmrc who will lose out with the difference.

Yes, however it does make a difference to what we pay ?

 

[Mihir]

Just for the benefit of everyone, here is an image from an excel sheet I created this morning to track my usage and savings.
My setup is 3.95kW Solar + 3.6kW Lux Hybrid Inverter + 4.8kWh Pylontech batteries + Octopus Go Faster Plan.
My setup includes filling up the battery if needed during the offpeak times at night so it can be used during the day.

In the above I have also included what it would have costed me if I wasn't on this entire setup based on the Octopus Go Faster peak rate tariff of 30.23p

Nov 2021: I had no Solar + Battery setup. No Octopus Go Faster plan.
Dec 2021: I only had Solar + Battery setup on Dec 16th onwards. No Octopus Go Faster. And I was still experimenting with the setup. But usage was already down.
Jan 2022: Octopus Go Faster from Jan 21st onwards. No EV yet. Still experimenting with the setup.
Feb 2022: MG ZS EV since 3rd Feb 2022. Setup was now clearly understood and working well. The usage includes EV charging.

The presence of Solar + Battery + Octopus Go Faster seems quite promising. Since the setup now is clear too, I am expecting a saving of between £65-£70 a month(may be more in summer months) giving me a total estimated saving of approx £800 a year and this includes EV charging as well!

 

[Dave]

Just for the benefit of everyone, here is an image from an excel sheet I created this morning to track my usage and savings.
My setup is 3.95kW Solar + 3.6kW Lux Hybrid Inverter + 4.8kWh Pylontech batteries + Octopus Go Faster Plan.
My setup includes filling up the battery if needed during the offpeak times at night so it can be used during the day.

View attachment 7213


In the above I have also included what it would have costed me if I wasn't on this entire setup based on the Octopus Go Faster peak rate tariff of 30.23p

Nov 2021: I had no Solar + Battery setup. No Octopus Go Faster plan.
Dec 2021: I only had Solar + Battery setup on Dec 16th onwards. No Octopus Go Faster. And I was still experimenting with the setup. But usage was already down.
Jan 2022: Octopus Go Faster from Jan 21st onwards. No EV yet. Still experimenting with the setup.
Feb 2022: MG ZS EV since 3rd Feb 2022. Setup was now clearly understood and working well. The usage includes EV charging.

The presence of Solar + Battery + Octopus Go Faster seems quite promising. Since the setup now is clear too, I am expecting a saving of between £65-£70 a month(may be more in summer months) giving me a total estimated saving of approx £800 a year and this includes EV charging as well!

Looks really good. Did you use a company to install the system?

 

[Mihir]

Looks really good. Did you use a company to install the system?

Yes, a Luton based company called SSU Renewables Ltd. Really nice people, knew their stuff and after sales service has been excellent too.

 

[Dave]

Yes, a Luton based company called SSU Renewables Ltd. Really nice people, knew their stuff and after sales service has been excellent too.

Thanks