Adding battery to existing solar PV system - any thoughts/advice please.

JKenH

IOF sounds very interesting. Are there any limits to system size on IOF?

I have a lot of room on my roof to add more panels. The limiting factor for me is the DNO. Although I have 7.3kW export limit I don’t get anywhere near that with my 7.8kW ESE/WNW system. Around 4.4kW was my peak output on the best solar day this year. I could squeeze 15kWp on the roof before I get into shading issues from my chimney. The extra panels would be useful in winter. 

Presumably there comes a point where the taxman gets interested and that is a redline for me. 

One other concern is with the expansion of grid scale solar will we get to a situation like in Australia where we might be charged for export at certain times. I certainly don’t seee how long term current domestic over export rates can be maintained. 

Screwdriva

JKenH said:

IOF sounds very interesting. Are there any limits to system size on IOF?

None whatsoever (other than G99).  And no tax implications either.

I would use this opportunity to maximize your panel coverage to target 8kWh in generation (your peak export allowance + assumed household base load) at a minimum. If it was my roof, I'd panel every inch of it

The beauty of IOF's automation is that the grid takes from your battery when your local grid needs it most, unlike PV only systems like mine, which can export only during the daily generation window. 

QrizB

JKenH have you still got the issue of the faulty panels in your current FIT-earning array?

Might this also be an opportunity to do something about those?

(Sorry for introducing yet another variable to the equation!)

pete-20-11

There could be tax implications if you generate 120% (or more) of your home's electricity needs / consumption. 

There is a £1000 trading allowance, after which tax could be payable. 

The rules were, I believe, designed more for businesses making a profit off solar rather than the average householder. But seek advice if you need to.

EricMears

Screwdriva said:

JKenH said:

IOF sounds very interesting. Are there any limits to system size on IOF?

None whatsoever (other than G99).  And no tax implications either. 

True - at the moment.  But who knows what Rachel will decide to do in November ?   

All those pre-election pledges limit her in most conventional methods of tax raising 

JKenH

Big thanks to @Screwdriva who came up with the goods. Before 9am I had a quote for the battery and tomorrow (yes, Sunday) the surveyor is coming out to do a survey and will then quote for the additional panels I require. That is what I call service.

Qyburn

Screwdriva said:

Qyburn said:

What's that, an overall 34p/kWh?

Just under 30p per kWh with a South aspect roof. 

I've been looking at IOF but haven't been able to take it further as Octopus have only just fixed my meter. I don't think it would be worth switching just now when production is ramping down.

Taking your example customers it looks like they're exporting 2,000 kWh per month. That’s twice our best month but if you assume the same degree of variation that probably equates to a range or up to 90kWh per day, average 60. How do you manage to get so much of that into the peak three hours?

JKenH

QrizB said:

JKenH have you still got the issue of the faulty panels in your current FIT-earning array?

Might this also be an opportunity to do something about those?

(Sorry for introducing yet another variable to the equation!)

Yes I have and it is something I have been thinking about but it’s just not economical to fix it. I am roughly 30% down on one string in my ENE roof and 16% down on one string in my WSW roof. Assuming the other strings are fine, (which they probably aren’t) I am losing about 400 kWh a year on the ENE roof and about 300 kWh on the WSW roof. That’s costing me about £140/year (5p FiT and 15p export/kWh). The defective panels are on two elevations of a two storey roof and the cost of scaffolding plus electrician to lift each panel to get to the underside plus maybe 3 replacement panels would, I suspect, be in the region of £1,500 so that’s around £2k per effective kWp.
 
I have now had a quote for adding 5 kW to my south facing roof for less than £5k (using the PW3 which I am going to get anyway as an inverter). That’s less than £1k per effective kwp. Pro rata £1500 invested on that roof would generate about 1400kWh and earn me 15p export at current rates so it makes more sense to invest in ne w panels than try and fix the old ones.

The other problem is that no one is interested in putting up scaffold to investigate the dodgy panels, re fixing them and then coming back after finding some matching replacement panels. I was thinking about ripping all the old panels off and replacing them with new but that causes FiT and DNO complications. My old panels (including inverters) cost me £7k installed for 7.8kWp and that 7.8kWp is now down to about 6.9kWp so is effectively still a relatively cheap system. If I scrap it and replace with new then I am chucking away around £7k worth of system on current values. It is cheaper just to bolt on some new panels if the DNO will allow it.

Screwdriva

Qyburn said:

I've been looking at IOF but haven't been able to take it further as Octopus have only just fixed my meter. I don't think it would be worth switching just now when production is ramping down.

Taking your example customers it looks like they're exporting 2,000 kWh per month. That’s twice our best month but if you assume the same degree of variation that probably equates to a range or up to 90kWh per day, average 60. How do you manage to get so much of that into the peak three hours?

IOF will stop delivering for most households from late October and begin again late March. A good time to switch to Intelligent Go or Cosy with the standard 15p export tariff. 

The household in question has 29 X 435W bifacial panels (with reflective background roof paint) for a ~12.6kWP system size - it has generated between 75-95kWh on a consistent basis, with outliers on both ends of that range. 

They begin exporting 11kWh from roughly 10:45am to 7pm. 4-7pm pays them over 30p per kWh (33kWh X .32p = £10.5) and the remainder of the day pays them their off peak rate in the mid 20p range for the 45-55kWh they export during the rest of the day (assume 45kWh X .24p = £10). Your mileage may vary. 

(Shared with permission of the owner)

JKenH

Screwdriva said:

JKenH said:

IOF sounds very interesting. Are there any limits to system size on IOF?

None whatsoever (other than G99).  And no tax implications either.

I would use this opportunity to maximize your panel coverage to target 8kWh in generation (your peak export allowance + assumed household base load) at a minimum. If it was my roof, I'd panel every inch of it

The beauty of IOF's automation is that the grid takes from your battery when your local grid needs it most, unlike PV only systems like mine, which can export only during the daily generation window. 

Apologies for my delay in responding (and also to @QrizB) but I had missed some of these messages which probably came in while I was typing another comment. Thanks for clearing up my system size limit query. Yes, I do foresee my DNO sticking its oar in.