Cost of adding solaredge to an existing system

Techoid

I've had a 4kw PV system for just over a year and been really pleased with it. I want to maximise what I can get from it and the company that installed it have recommended fitting solaredge technology (I went to them about it). What I can't work out is whether it is worth doing- costs a lot fitting it onto an existing system (I am quoted £3200). Is the return over 19 years plus likely to get close to that? I like the idea of being able to monitor the panels, and I am happy that I will be optimising the amount I am generating, and presumably future-proofing when it comes to possibly adding a battery.
I have two arrays and a shading factor of 10% according to the original survey. The system generated 3590 units in a year, about 108% of the survey forecast. Any advice welcome, thanks!

EricMears

Techoid wrote: »

I've had a 4kw PV system for just over a year and been really pleased with it. I want to maximise what I can get from it and the company that installed it have recommended fitting solaredge technology (I went to them about it). What I can't work out is whether it is worth doing- costs a lot fitting it onto an existing system (I am quoted £3200). Is the return over 19 years plus likely to get close to that?

I have two arrays and a shading factor of 10% according to the original survey. The system generated 3590 units in a year, about 108% of the survey forecast. Any advice welcome, thanks!

If the original survey was accurate then the best you could hope for would be to get 10% more output - although even SE isn't going to remove all the shading effects.

Not sure what you get per unit (I know it will be nowhere near my 50p) but the benefit of an extra 350 units is unlikely to offer much of a return on £3200. Another story completely if your inverter should fail and you have to buy a new one but that's not going to be any time soon.

Martyn1981

Hiya, and welcome.

I have SolarEdge on my WNW system, and have twice researched an upgrade on my ESE, but not found it viable.

I think your best starting point is to compare your annual generation to PVGIS estimates.

3,590 is reasonable for a south facing system in the north, but perhaps a bit low, for one in Cornwall, so we need a bit of comparison.

Also, you mention two arrays, which might have the same orientation, or perhaps be E/W split, in which case your generation is pretty good.

Once we have a comparison, we can see potential gains, and from there work out income v's expenditure.

I love SolarEdge, but you'll need a lot of shading losses and performance losses to repay £3,200, especially on a 16p(ish)? FiT rate.

Mart.

Techoid

Thanks- the two arrays are facing the same direction (SSW- ish) and I am in Suffolk. What I've noticed is the lower of the two arrays is affected by shade from next door's roof as the sun gets lower- starting in October as the apex catches in the middle of the day and getting quite significant during the winter months, but this wasn't indicated in the original survey report- perhaps because it is not significant given the time of the year? Fit rate is 12.9p. Given the fact I'm going to make a fair return on the system anyway over time I don't mind if this doesn't quite cover itself, but I don't want to feel fleeced if the actual gain is very small. The sales chap reckons that on a 20% increase in production I should more than cover the cost, but I can't quite work out how!

EricMears

Techoid wrote: »

Fit rate is 12.9p.
The sales chap reckons that on a 20% increase in production I should more than cover the cost, but I can't quite work out how!

IF the original estimate of shading at 10% was accurate then that's the absolute maximum increase you could expect.

But maybe he's recalculated the shading factor at 20% ? You are now in a position to calculate the actual shading factor by comparing your first year's results with the PVGIS forecast. Strictly, that forecast is only the average of the last 30 years but a whole year that's more than a couple of percent different from the mean would be unusual.

Assuming that his 20% is now an accurate figure and given your FIT rate of 12.9p (is that the actual FIT rate or should you be adding in half the deemed export rate ?) he should be calculating an annual benefit of 700 units @12.9p or around £90. Are you happy with £2200 (whoops !) earning you £90 p.a. ? That's approx. 4% (and based on very optimistic assumptions !). I'd want a lot more - but maybe I'm just greedy. True, it's more than you'd get from a savings account this year but over the next 19 years interest rates are almost bound to rise.


edited later:
Don't know where 'my' £2200 came from. Using the correct £3200 my 4% drops to 2.8%

Martyn1981

Techoid wrote: »

Thanks- the two arrays are facing the same direction (SSW- ish) and I am in Suffolk. What I've noticed is the lower of the two arrays is affected by shade from next door's roof as the sun gets lower- starting in October as the apex catches in the middle of the day and getting quite significant during the winter months, but this wasn't indicated in the original survey report- perhaps because it is not significant given the time of the year? Fit rate is 12.9p. Given the fact I'm going to make a fair return on the system anyway over time I don't mind if this doesn't quite cover itself, but I don't want to feel fleeced if the actual gain is very small. The sales chap reckons that on a 20% increase in production I should more than cover the cost, but I can't quite work out how!

I'm with Eric, the numbers don't add up. Let's add in the export at 2.455p/kWh (deemed 50% of generation), then you get:

3,590 @20% = 718 x 15.355p = £110pa, or £2,095 over the next 19 years, v's the £3,200 cost of doing it, so you lose over a grand.

Personally I'm totally with you on maximising generation, and being willing to invest, so perhaps a better idea would be to put the £3k into an environmental investment scheme(s).

I've invested in several Abundance green schemes. That way you (or at least your money) is still generating clean leccy. In fact if you invest in a diverse spread like wind and hydro too, then you can 'stick your fingers up' so to speak at folk who say you only generate during the day, since some UK generation will be down to you, at most times, accounting for most of your consumption, not just in net terms, but possibly all the time(ish).

Martyn1981

Techoid wrote: »

Thanks- the two arrays are facing the same direction (SSW- ish) and I am in Suffolk.

Quick check on PVGIS suggests about 3,870 for 4kWp at SSW.

So assuming some shading (+10%) and the SolarEdge kit maxing out the performance of every panel (+10%), then looks like 20% is probably the best you could hope for. Nice, but not enough for a retro-fit.

pinnks

I have wondered about upgrading my systems but concluded it is not worth it.

My shading is in the afternoon in the summer when I could get up to 3kWh per day more from my smaller array. I also get winter shading from both systems but to be honest any savings from that would be no more than frosting on the icing on the cake.

I do find the suggested price somewhat high, not least because I understand you can now add SE to a non-SE inverter using a £200 or so interface thingy. I calculated it would cost between £1000 and £2000 to upgrade mine depending on how much I got shafted for scaffolding and labour, so £3200 looks crazy.

Either way, like Mart, I reluctantly decided the payback would take too long to warrant the expense. I am just learning to live with my slight frustration at not having had the understanding of shade which I now have... We are all so wise with hindsight!:beer:

DREKLY

Interesting thread: did Martyn mention Cornwall just now ? (Hi Martyn, I am a regular lurker on this forum, as well as others....)
"3,590 is reasonable for a south facing system in the north, but perhaps a bit low, for one in Cornwall, so we need a bit of comparison."

4Kw Solaredge system here, 230 degrees, so SW facing, estimated 20% shading before install, first year has produced 3524Kw - August 2015 to July 2016
it falls flat on its face after end of October due to neighbours 60ft high beech trees, i.e. my Nov output was a measly 80Kw (PVGIS indicates 155 for my location) but its way up on last year's November which was 58 Kw !!!

My Fit rate inclusive is about 15.5p, rounded down, so looks like Techoid is in the same boat as me, but with a smaller sail !
Hope this info helps.... cheers

Martyn1981

Thanks DREKLY. That's a good point, we can look at the maximum possible, and SE kit can help stop the 'shading disease' from spreading to other panels, but it can't magic sunshine from nowhere if there is heavy shading.

For the OP to get all of that 20% extra, their shading would need to be more panel specific, resulting in a larger drop across the whole system. If it's like yours and hitting most of the system at times, then nothing you can do about it ..... short of a chainsaw!

Martyn1981

pinnks wrote: »

I do find the suggested price somewhat high, not least because I understand you can now add SE to a non-SE inverter using a £200 or so interface thingy. I calculated it would cost between £1000 and £2000 to upgrade mine depending on how much I got shafted for scaffolding and labour, so £3200 looks crazy.

When I had the WNW system installed with SE kit I asked the installer for figures on upgrading my ESE systems. He quoted £2,300 plus scaffolding (I'd gotten the WNW done for £180 plus 2 cases of lager).

I didn't go for it as we were about to cut down a tree, and I think replacing the two inverters with a single, more efficient one would do half the work.

More recently I got one of those calls from the upgrade guys (had loads since). I was very negative, but agreed to a visit when they suggested £2-£2.5k. This happened just about when the inverters 5yr warranties ended, and they said they'd fully warrant the whole system (my installer went bust).

After 2hrs of BS, the saleslady finally quoted me £4.6k, which I laughed at and pointed out that was the cost of a whole system. We didn't end up on best of terms as she told me not to go with the upgrade as I was clearly happy to pay £3.5k every 5yrs for new inverters! I told her I was .... as I walked her to the door.