Advice/Suggestions please.

[Thebeeman]

I currently have 3.8 Kw of panels on a Fronius inverter installed 2011, Inverter renewed 2018, great FIT payments.
August last year I had 10.5 Kw of pylontech via a Luxpower inverter installed, I'm shortly going to add another 5 Kw of battery.
I want to add some extra panels, space is not a problem. Definitely not touching the original system.
Do I go with another stand alone, panels and inverter or add panels and swap out the Luxpower for a Solar and battery version and 'sell' the old on Ebay?

[Stinsy]

You can do either.

That said, a 3rd inverter would raise some eyebrows at the DNO and you'd possibly be denied.

I'd recommend swapping out the existing battery inverter for a hybrid unit. You can get very good prices for used inverters on eBay.

I have encouraged people adding batteries for a FiT system to buy a hybrid even if they aren't fitting additional solar now because it gives the option of adding solar later...

[Countrypaul]

You don't say why you want the extra battery and panels whch may help direct you in the best direction.

If your existing inverters can produce enough power for say 95%+ of the time, then is another option may be to use panels connected to a charge controller direct to the batteries?

[Thebeeman]

Currently 'most' days I can get by not charging on off peak but as we go forward the charging sessions are going to increase. Some days I'm exporting with a full battery but shortly I'll be lucky to get 100% during the day hence possibly more panels. The extra battery is to stop export as I don't get paid for it I would get more 'cheap' power in the shed overnight to cover more of the following winter day. I hope that makes sense to someone other than me.

[Joeboy]

Currently 'most' days I can get by not charging on off peak but as we go forward the charging sessions are going to increase. Some days I'm exporting with a full battery but shortly I'll be lucky to get 100% during the day hence possibly more panels. The extra battery is to stop export as I don't get paid for it I would get more 'cheap' power in the shed overnight to cover more of the following winter day. I hope that makes sense to someone other than me.

The above is exactly what we did. I am in the first full.year with the completed system. PV has been immense with some days admittedly where there has excess although not as bad as I thought. I've managed to shift it around and use most of it. Having the EV makes a huge difference to generated use and being able to run the EV for months on end offgrid has been a joy.

Increasing the battery stack size was like a tension switch got flicked to the off position. I have no worries at all and enough stored to take care of any eventuality in a 24hr cycle. If I had to I could likely push it to 48hrs. Might test that this Winter.

Geographically and layout/shading isn't the best but self generation of over 7MWh pv pa and a chemical storage capacity of 99kWh (EV&home) makes a huge difference.

Hot water takes care of a further 12kW and storage heaters do the rest (unless it's cooking outside then I let it go).

All in we have a total storage capacity of 208kWh which is surprising when written down. Even more surprising is that the majority of that is in non chemical storage and cheap to purchase and operate. Worth a thought?

Do you have a preference to which you'd do first beeman PV or storage?

[Stinsy]

Currently 'most' days I can get by not charging on off peak but as we go forward the charging sessions are going to increase. Some days I'm exporting with a full battery but shortly I'll be lucky to get 100% during the day hence possibly more panels. The extra battery is to stop export as I don't get paid for it I would get more 'cheap' power in the shed overnight to cover more of the following winter day. I hope that makes sense to someone other than me.

I think you’ve come to the right place! Many on here have been there and done that. Once you see a working system you want to fill the gaps of storage and generation.

Batteries make solar difficult to justify financially because you’re offsetting cheap rate electric with solar. So instead of your solar stopping you consume 30p electric the solar stops you consuming 7.5p electric. So if I were you I’d do the battery upgrade right now in preparation for winter.

I’d still do the solar upgrade personally. Just realise you’re doing it ‘cos you want to rather than because it makes sense. You know those days in summer when your existing setup generates more than you can possibly use? With a bigger system you’ll generate even more on those days. You know those dark midwinter days when your existing system generates little-to-nothing? A bigger system won’t help you out at all on those days. A bigger system is for the days in between, the bright-overcast days, the days where you get a few brief spells of sunshine. How many of those are there?

Do you have a DHW tank? If so a diverter will help put your excess solar to use.

[Joeboy]

Currently 'most' days I can get by not charging on off peak but as we go forward the charging sessions are going to increase. Some days I'm exporting with a full battery but shortly I'll be lucky to get 100% during the day hence possibly more panels. The extra battery is to stop export as I don't get paid for it I would get more 'cheap' power in the shed overnight to cover more of the following winter day. I hope that makes sense to someone other than me.

I think you’ve come to the right place! Many on here have been there and done that. Once you see a working system you want to fill the gaps of storage and generation.

Batteries make solar difficult to justify financially because you’re offsetting cheap rate electric with solar. So instead of your solar stopping you consume 30p electric the solar stops you consuming 7.5p electric. So if I were you I’d do the battery upgrade right now in preparation for winter.

I’d still do the solar upgrade personally. Just realise you’re doing it ‘cos you want to rather than because it makes sense. You know those days in summer when your existing setup generates more than you can possibly use? With a bigger system you’ll generate even more on those days. You know those dark midwinter days when your existing system generates little-to-nothing? A bigger system won’t help you out at all on those days. A bigger system is for the days in between, the bright-overcast days, the days where you get a few brief spells of sunshine. How many of those are there?

Do you have a DHW tank? If so a diverter will help put your excess solar to use.

I'd go battery first and plenty of it, hybrid inverter 2nd, more solar 3rd and next year. Gives the OP a decent timeline to maybe snag some sales or secondhand panels. I found that we kind of expand into the extra battery capacity? Is there such a thing as too much? SWMBO.says so and we are good to go now.

[Thebeeman]

Thanks all. As suggested I'll add at least another 5 Kw of battery for this winter, I can do that DIY, and ponder further for next year. As we're both 73 the payback time needs to be fairly quick for us to benefit.

[Stinsy]

I'd go battery first and plenty of it, hybrid inverter 2nd, more solar 3rd and next year. Gives the OP a decent timeline to maybe snag some sales or secondhand panels. I found that we kind of expand into the extra battery capacity? Is there such a thing as too much? SWMBO.says so and we are good to go now.

I agree.

[Thebeeman]

Just for info. I've just bought a 5Kw Pylontech battery for £1255.50. Vat included but not carriage, I'm close enough to collect. That price is with a 10% sale discount.

https://callidus.shop/products/pylon-us ... -pylontech

If you are looking for one now seems to be the time.