Solar Panel Advice - Second system

Jimmyrn85

Jimmyrn85

Jimmyrn85

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Location
Cornwall
Good afternoon all!

I've recently moved into a house which has an existing solar system.
The system is around 12 years old, it is 3.96kw. South facing. 12 panels, my man maths states that they would be 330w panels and probably significantly less than that now due to their age. There is a large Growatt inverter in the loft (I'm unsure of the model).

There is a lease arrangement in place. Which getting the right paperwork from the seller to satisfy my lender was a nightmare (basic things like was the system installed by a competent company). The basics of it are.... The system was installed for free for the previous home owner. The home owner can use as much of the lecci generated at any given time, the homeowner cannot store any of this lecci. The panel installer gets the nice FIT payment which was available 12 years ago. There is 13 years left on this lease. The solar company takes care of any maintenance required and that is that.

So far... I'm happy, I've noticed a reduction in my lecci bills from only being in the house a few months compared to my previous property (and of course we have had nice weather in southern England recently!) With me and the Mrs working from home and using the dishwasher / washing machine during the day it pretty much covers all our loads. Our heating and hot water is gas.

This leads me on to a question for you all please.... especially after reading the wonderful DIY post by Ron-Ski.

There is a decent amount of roof space on the garage, which is also south facing.

Can I, install a second solar system (another inverter, bunch of panels, batteries and any other auxiliaries as required) which is grid tied, but is not allowed to export?

Thinking out loud... A second system would charge batteries during the day, then as the leased system runs out of sunlight in the early evening, can the second system be set to start discharging the batteries to maintain house loads? Would there be no need for G99 stuff because there is already an approved system in place for exporting?
If this is achievable, any advice and guidance would be much appreciated.

Am I able to as a reasonably competent DIY'er (not to Ron-Ski's level) install the solar panels on the roof and connect up to a new inverter but get a proper sparky to do the connection to the house consumer unit? I notice Ron-Ski had the sparky connect the panels up too.

Cheers!
 
Seems from a quick google it would be possible to add a second system but will require permission and cant go through the same FIT meter.

Out of interest how would you get out of that deal / lease so you could replace it all?
 
Thanks SJA. I don't want to feed in, want nothing to go to the grid, but I still want it grid tied (so it can easily connect to my house mains and power the house via batteries).

You can buy your way out, but it is very expensive and not worth doing. It is a sliding scale, but it's like 20grand at the moment.
 
I would never have bought a house with a rent a roof PV system on it, if you ever need to replace the roof, they will likely charge a fortune to remove and refit their system, and want compensation for missed generation, perhaps that would be the time to buy out of the lease.

If the contract stipulates you can't store any of the electric, then adding batteries could be problematic, I think you'll need to clarify this with the leaseholder. If they are on deemed exports, then I can't see why they care whether you store electric in a battery or not, as it would make no difference to them.

Yes, you could in theory add solar and batteries to the garage, you will need G99 or G100 as the new inverter will be connected to the grid, regardless of whether you want to export or not.

Depending on how the existing system is installed, it may make things tricky, usually the battery system will see what you are pulling from the grid, and then increase output to match, and if exporting it will try and store that in the batteries, thus send as little as possible to the grid.

It can be done, but depends on the system you install, and/or how the other PV system is connected up. Is the current system connected directly to the consumer unit?

I got the sparky to connect the panels, as they had the proper crimping tool to crimp the MC4 connections.
 
It's a risk as you've highlighted, however the pros outweighed the cons for us, location is exactly where we wanted to be.

I don't want to add batteries to the existing system, I'd like to make a totally separate system in the garage. But if you think it will interfere with the original system then I guess I will talk through my options with them.

Thanks for the info on the G99/G100.

Yes this is the interesting part I feel, if the new system could be somehow configured to not do anything but store energy during the day (maybe even isolate it from the main consumer unit during the day?) then as the sun goes down, it is then connected and allowed to support the house loads but send nothing back up to the grid.

Current system is connected directly to consumer unit, has it's own meter (or a standard export meter) I don't know much at all about that extra meter.

Thanks, makes sense ref the MC4.
 
The extra meter is the generation meter, that's what the FITS payments are paid from, presumably you, or someone reads this meter.

Do you have a smart meter, or an export meter?

I got my FITS system in 2015, and I got smart meters soon afterwards, so I could see I was exporting more than 50%. I enquired if my FITS provider could use the export reading from the smart meter, they said they couldn't as it wasn't certified for export and I'd need a proper export meter at about £400.

If they are on deemed export then I really can't see why storing the excess power would be an issue, so definitely worth enquiring.

If they won't let you store the power, then you need to get the tails to the consumer unit split, and fit a separate consumer unit for the rent a roof PV. Your new system can then be connected in to the existing consumer unit, and it's CT clamp fitted to the tails of that consumer unit, this means the battery will never see the rent a roof system, which also means all the time you have sufficient battery and your own PV generation you'll never use anything from the rent a roof system as your new system will try to cover all House loads.

You could get around that limitation by using software, but you need an inverter/battery system that has that control, possibly using Home Assistant. I do similar when my car charges on IOG outside off peak times.

It really boils down to what the rent a roof people will let you do, so much easier, and better for you if you can store generation from the rent a roof system, or whether they are OK for you to use software to control it.
 
I have 3 smart meters, lecci and gas and solar. The meter to do with the solar gets read by them remotely, basically the homeowner has nothing to do with the system. My hunch is there isn't a deemed export, it is all metered.

Thanks for info, I'll make some enquiries and start plotting!
 
If their only meter is between the consumer unit and inverter then they are on deemed exports, and it also wouldn't make sense for them to be on metered exports.

Let us know how you get on.
 
Yes there is a buyout clause, but it is not in their interest to sell it to you, hence it's very expensive. I don't have the figures in front of me but it is something like 20grand to buy it out now (it's about 12 years old) and it decreases each year but not by much!
 
Jimmyrn85 said:
Yes there is a buyout clause, but it is not in their interest to sell it to you, hence it's very expensive. I don't have the figures in front of me but it is something like 20grand to buy it out now (it's about 12 years old) and it decreases each year but not by much!
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Only one way out of it, and you need to check the T&C's - Have the system condemned as dangerous by another electrician and get it disconnected, they then have to prove it is safe, sometimes it isn't worth their time and aggravation and they'll agree to let you remove it.
 
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Mercenary Keyboard Warrior said:
Ah ok thats a shame. I know contracts vary a lot.

Whats the end of 25 life options?
Do the panels resort to being yours or theirs or what?
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Haha good question! Yes around 2036 lol... It becomes ours (or the next home owner!) or you can get them to remove all the kit at their expense. Will it still be working by then? Will 300ish watt panels be capable of 50w then?! lol. If it breaks, they cover costs etc up till then.
 
Journey said:
Only one way out of it, and you need to check the T&C's - Have the system condemned as dangerous by another electrician and get it disconnected, they then have to prove it is safe, sometimes it isn't worth their time and aggravation and they'll agree to let you remove it.
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Interesting angle!

I'm not sure it would wash! I had to get certs to confirm it was installed correctly by a certified company etc etc to satisfy my lender.

Also, I'm not unhappy with the system! Even if the terms seem to suck! I get free lecci during the day. I'd just like to have a second system, but also connected to my consumer unit to power the house in the evening.

I have had a look through my T&C's whilst I'm on the ship here:

2.4 If the Landlord wishes to carry out alterations or additions to a part of the Building which is in the vicinity of the PV System or any conduits serving the PV System, then the Landlord may do so if the Tenant first consents to this in writing and, if the Landlord demonstrates to the Tenant that such alterations or additions will not interfere with the operation, efficiency, productivity of or access to the PV System then consent will not be unreasonably withheld or delayed.

3.2 The parties agree that any electricity generated by the PV System may be used by the Landlord for the benefit of the Landlords Property and that any electricity which is not used will be exported to the grid for the sole benefit of the Tenant.
 
That to me reads that you are able to install a second system, and you are able to store electric from the rent a roof system, you will be storing that electricity for the benefit of your property, once the battery is full, any not stored will be exported. You just need their permission.

Unless there is another clause which specifically excludes storing it, I'm not export but I'd argue the above permits you to store it, and install a separate system, with their permission.
 
Jimmyrn85 said:
Haha good question! Yes around 2036 lol... It becomes ours (or the next home owner!) or you can get them to remove all the kit at their expense. Will it still be working by then? Will 300ish watt panels be capable of 50w then?! lol. If it breaks, they cover costs etc up till then.
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As long as they are reasonable quality panels, haven't seen too many extremes of hot or cold weather (they are pretty robust but this can increase degradation slightly to moderately) or shading issues (this can cause moderate to major degradation) then they should still be operating at over 80% of their original capability (if clean).
 
Jimmyrn85 said:
Haha good question! Yes around 2036 lol... It becomes ours (or the next home owner!) or you can get them to remove all the kit at their expense. Will it still be working by then? Will 300ish watt panels be capable of 50w then?! lol. If it breaks, they cover costs etc up till then.
Click to expand...

At least it becomes yours and doesn't require you to buy them out so it can be removed. Some of the leases do have this.

25 year old panels wont be too bad. It varies but now they seem to think loss of 0.2-0.5% per year so you should be at 80% still.
Obviously thats average, panels will vary and depending on the exact panels one bad one could affect the others.
Eg the bipass diodes are now very common but far less common on older panels.

Is it still original inverter? Thats the most likely thing to fail on a solar system.

The problem with a straight replacement is that the older panels were generally smaller (easier to ensure consistency) so there may not be an easy straight swap. but in general if nothing major has happened I would just stick with the panels and update the rest potentially.
If the panels have issues though I would go straight to replacement panels and wiring at that point. No point messing about with 25 year old panels.

Agree with ronski in that those T&Cs you presented don't seem to exclude adding batteries. Although its a little more tricky if you have a string inverter (almost 100% likely) its certainly possible.

I can see why they would want to exclude you from messing about with the system but you could install an AC coupled battery that doesn't touch any of their wiring.

To me it sounds like you could install another system on the garage without asking their permission, the only get out would be if they use the garage roof as access.
You may have export issues though, assuming they have it setup as a 3.68kw system, you would either need to completely disable export on the second system, or get them talking to limit your new one to only the excess available (without causing the old one to clip)

Do the people who come round work for the original supplier do you know? That would be a good place to start IMO.
 
The original inverter is irrelevant, as you need to leave that system well alone, the OP doesn't want to connect batteries directly to it anyway.

Adding an additional system should not cause the rent a roof system to clip, plain PV systems with a peak capacity within DNO export limits never used to have CT clamps. If that is the case and the DNO limits export, then the new system will have to clip (restrict) it's generation.

Lots to be considered, but should all be doable.
 
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