New solar installation and questions

Martyn1981

Hiya Alan, I've got a slightly different view to others on this.

If your current system has a capped inverter, probably 3.68kW, and you plan to put more PV through the same inverter, then you wont need to ask the DNO for permission, though they may need informing about the new size of system, making it clear that export is still capped at 3.68kW.

The DNO is only interested in the (theoretical) output of the SSEG (small scale electricity generator). So it's the inverter that's important. In my case, it's back to front - to gain permission for my WNW extension I had to send them the certification documents for all three of my inverters. As my inverters add up to 5.9kW, they issued me with permission for 5.9kW of output, even though my panels are only 5.58kWp. They also confirmed that I didn't need additional permission for more panels, so long as they were run through the approved inverters.

With regard to FiTs, if you add more panels to the same inverter, then you'll be putting more generation through the TGM. I'm not sure how this all works now, as things changed recently, however, I'd assume that they'd simply apportion generation, so 4/5 eligible, and 1/5 non eligible.

Best bet is to ask your FiT provider for advice. As others (and you) have said, don't do this sneaky, you'll get caught and lose the whole deal.

Mart.

pinnks

Hi Alan,

I am more keen on diverters than Sterlingtimes but then I do not have an export meter. My system was 3.5kWp but I then extended it to 5.25kWp, but that said my larger system faces west and produces little before midday.

My experience with the immerSUN (which for an extra £99 has a monitoring system) is that I turn my gas off for nearly 6 months (mid April to end Sept or so) which saves me about £80. Add to that some top-up hot water on days like today and my guess is payback of about £100 per year based on 2 1/2 years. Don't forget that you could have high losses in your pipes from boiler to tank when using the boiler only for hot water, so its not simply a question of calculating the kWh diverted at gas rates. For me the reduced gas bills tell me the real saving but it equates to the diverted amount at leccy rates (conveniently...)

immerSUN is more expensive than some of the others like iboost but I am content with my purchase and it can power three separate devices (1 at a time) which I don't think the others can. You can also cascade up to 5 immerSUNs if your system is big enough to service them all. I have 2 but that is because it was easier to cascade a slave unit to power my radiators than to run hidden cables and use unit one to do the job. It also has the monitoring capability (look at https://www.myimmersun.com). I use mine to run oil-filled radiators too in those in-between months and on days like today.

If you just want to monitor import/export etc you could look at https://www.your-loop.com. My brother told me about it recently. He doesn't have solar but likes what the system offers and I think it can monitor export like the myimmerSUN.

If you search on immerSUN on this forum you'll find a lot of my ramblings on this and thoughts of others. Search on iboost you will find good info too but also a lot of comments about my quote include and iboost and so on.

good hunting...:beer:

pinnks

Decided to browse the Loop site and found this:

Loop cannot currently measure export energy and therefore it is not possible to use Loop accurately if your household has solar panels or a wind turbine. We are working on a version of Loop which supports generation which will be out soon.

So doesn't perhaps do quite what I thought it did for us with renewables

Alan_Brown

Thanks for the help guys.

Martyn1981 - This was what the installer was proposing, just having the 3.6kw capped inverter with the 5kw panels. The quote stated that the installation would lose efficiency on very sunny days as some generation over 3.6kw would be lost, but that we would gain on less sunny days by having more generation. I was quite happy with that approach as it seemed more straightforward. In the end my finances stopped me from going down the 5kw route as I'd need not only the extra 4 panels but a different type of inverter with some other kit that attached to each panel. This was because we would effectively be installing on three different roofs, with the two easterly ones having different light conditions.

pinnks - thanks for the information on the diverter. I think I will give it a go when I can afford it and see how I get on. If we aren't getting the savings from diverting then I can always look at adding the extra panels to increase supply.

EricMears

Alan_Brown wrote: »

Hi, thanks for welcome. I think I may have given the wrong impression when I mentioned adding the panels without telling anyone. I'm not menaing to be unethical I just meant without applying for tariffs.

If I need to legally tell the authorities then I would. I suppose that's my next question. If I add extra capacity, is there anyone I need to tell if I'm not going down the tariff route?

What are the consequences of adding the extra panels? Sorry, they may be obvious to people on here but not to me When I got the original quote I had a quote for 4kw and a quote for 5kw. I couldn't afford the 5kw and settled for the 4kw. I asked the solar company if I could add the 1kw at a later date and they were a bit cagey and said no. I just assumed this was because they wanted to do it all in one go and get the extra money? I didn't delve any further with them.

You'd really need to include an extra inverter (and its own generation meter) so that the additional generation doesn't get mixed up with that for which you have a FIT contract. Anything else would probably mean that your FIT payment company would be making silly assumptions about how much of your future generation was eligible for payments (and you can be fairly certain that their assumptions wouldn't work out in your favour !).

Alan_Brown

EricMears wrote: »

You'd really need to include an extra inverter (and its own generation meter) so that the additional generation doesn't get mixed up with that for which you have a FIT contract. Anything else would probably mean that your FIT payment company would be making silly assumptions about how much of your future generation was eligible for payments (and you can be fairly certain that their assumptions wouldn't work out in your favour !).

Do you know how would it work with the current FIT payments? If I had gone above 4kw, the FIT payments would reduce slightly, but now with the huge drop, would my 5kw drop me to the current >4kw rate or the >4kw rate that was in force when I had my install carried out?

EricMears

Alan_Brown wrote: »

Do you know how would it work with the current FIT payments? If I had gone above 4kw, the FIT payments would reduce slightly, but now with the huge drop, would my 5kw drop me to the current >4kw rate or the >4kw rate that was in force when I had my install carried out?

Providing you don't do anything silly, the FIT contract remains in force for the full 20 (or 25 if you were an early adopter) with your current rate escalated in line with inflation.


An extra 1kW would be at the rate for >4kW (if you choose to claim it - or zero if you take the view it's not worth claiming).

pinnks

When I added my second system I added a second inverter and meter but feed both into a single cable back to the fuse box. My FiTs on the old system are at the <4kWp rate and for the new system at the >4kWp. I have 2 accounts with my FiT provider, each running for their own 20 years.

Had I not gone down the 2 meter route (either with 2 inverters feeding into one meter or one inverter for all panels) then the FiT provider would have apportioned production between the two systems. I have 14 panels on one roof and 7 on the other. Whether they would have done a 14/21 and 7/21 apportionment or tried to reconcile the slightly better annual production from the smaller south-facing array remains to be seen. If they had I could have lost out slightly but if they had not I would have gained a little because some of the south-facing production would have been paid at a higher rate.

Personally, for the cost of a generation meter, I would go for two clean systems unless your original inverter has capacity to deal with all panels, or you were going to replace the existing inverter with a single larger capacity one - but then you might get issues with size of strings and balancing arrays and so on...

Martyn1981

Alan_Brown wrote: »

Thanks for the help guys.

Martyn1981 - This was what the installer was proposing, just having the 3.6kw capped inverter with the 5kw panels. The quote stated that the installation would lose efficiency on very sunny days as some generation over 3.6kw would be lost, but that we would gain on less sunny days by having more generation. I was quite happy with that approach as it seemed more straightforward. In the end my finances stopped me from going down the 5kw route as I'd need not only the extra 4 panels but a different type of inverter with some other kit that attached to each panel. This was because we would effectively be installing on three different roofs, with the two easterly ones having different light conditions.

Hi Alan. With your system split E/W I doubt you'd see any significant capping. Effectively you'd have 3kWp E + 2kWp W. On a sunny day in the summer when the sun's high and able to hit all panels, total gen may exceed 3.68kW, but probably not by much, and those days are rare. My system can hold 4.2kW, so jumping to (too many) conclusions, (4.2/5.58(me)) x 5(you) = 3.76kW. Also with different conditions/pitches on the East systems, you'd expect lower peaking too.

But, and this is a big BUT. What inverter do you have? If it's a SolarEdge system then you should be able to add more panels, but if it's a normal dual MPPT inverter, with one MPPT for E and one for W, then there's a problem.

You won't be able to add a third string to the inverter. And even if the MPPT's allow 2 connections each, they'd have to be balanced - same kWp, same orientation and ideally same pitch. So you couldn't have a 2kWp and a 1kWp string together.

If you could simply add the 1kWp to your system, that would be fairly cheap, but small system, plus inverter, plus TGM etc, and the cost will be proportionately high.

Back to extensions, you'll find info in section 10 of the FAQs, but ....... and it's another big BUT, I think another change to the FIT rules is that you only get one chance now to claim for FiTs, so no extensions are allowed. What I don't know is if that rule applies to all systems, or only those installed under the new incoming FiT.

Best bet, have a chat with your FiT provider, and also post the make and model of your inverter, which might answer a lot of questions.

Nothing stopping you doing a non FiT install, but as others have said, if you need an additional inverter, then you'll also need DNO approval, since they'll rate the system on theoretical output, and won't take panel orientation into account, so you'll have 5kWp of panels, and (presumably) 4.68kW of potential inverter output.

Sorry the news couldn't be better.

Mart.