Solar Panel Guide Discussion

Martyn1981

Hemel_Saint wrote: »

Hi All

Mark

Hi Mark. Some quick points, but mostly I'll descend into a long boring post.

I agree with T and Cardew that the voltage optimiser is a waste of money, you'll save next to nothing.

Water heating diverter. Don't price savings against the fuel cost, as there will be losses in the system, increasing fuel consumption by perhaps 50% to 100%, whereas leccy is roughly 100% efficient. So diverting 1,000kWh of leccy to water heating could replace 1,500 to 2,000kWh of oil heating. If you can get this done for £200 or so, then the returns are probably good, have a play and see.

T raises an important point about the DNO (District Network provider). If you install a system that can export more than 3.68kW, then you'll need prior approval. You can get around this by capping your system to 3.68kW. Your losses won't be too high given the split nature of your system, and the NE roof won't be great, especially given the roof pitch. For instance a random pin near Worcester suggests 626kWh/kWp for 30d pitch, but 539kWh/kWp for a 45d pitch (both with orientations of -135d) according to PVGIS.

It would be better if you could have an inverter closer to 5kW.

Speaking of which, as T says, if you have no shading then it might be simpler to use a normal inverter. Both T and I have SolarEdge systems, they are great, but you do have extra kit on the roof if it goes wrong.

There are loads of inverters that should work using 1MPPT (maximum power point tracker) per roof, effectively treating each roof as a separate system. This is needed, as otherwise the lower performing roof will pull down the other roof.

These are examples of inverters that will work, but there are many more, and I'm linking to a shop that's currently closed, just because it's a quick way to locate products:

SB 5000TL Dual Tracker

Samil Solar River 5200TL-D 5kW Dual MPPT

Solis 5.0kW Dual MPPT

You'll note a large price difference.

For a capped inverter, this would work:

SMA SB3600TL-21 SunnyBoy Dual Tracker (3.68kW)

There's more info on PV in the PV FAQ's.

Price wise, T's better at guessing than myself, but I'd have also thought £6k was possible if you shop around.

I seem to have waffled off course, so leave you with that for now. Just keep chatting and asking questions.

Mart.

Cardew

Hemel_Saint wrote: »

If there is any further information you need from me, please just ask.

cheers
Mark

Did they give any forecast of income/savings - with a breakdown?

pinnks

I would echo what's been said.

My understanding of voltage optimisers is that they might have a marginal impact with wire-wrapped transformers and old-style light bulbs but have no impact whatsoever with switch mode power supplies which are in virtually everything these day, or with LED lighting. So, at £700 it would take about that many years to recoup the investment, if it lasted that long (not to mention your longevity).

On a more serious note, I agree with Mart about the diverter payback costing. My records show that I use about 3 times as much gas to heat water as I do using the immerSUN. This is because of losses in the system between boiler and tank (about 22m, 22mm unlaggable copper pipe return trip). I save about £80 of gas over the summer when the heating is off and all hot water comes from the diverter. over the other months I get a contribution to the water - perhaps £20?. My system is 5,250Wp, so if you are going large you may get similar results.

Exiled_Tyke

tunnel wrote: »

In short

I'd expect 24 panels fitted for between £5.5k-£6.5k dependant on your location and your bartering skills. At £9250 I'd be asking for a 6kW battery storage system thrown in.
Forget the voltage optimiser
You can get an immersun/iboost for the immersion for under £300 fitted now.


Do you have any shading on any of the rooves?
If not then a standard dual MPPT inverter would suffice, less cost and less things to go wrong on your roof


You'll also need DNO approval for a 6kWp system, make sure that that is included with any price quoted.

Great advice all round which leads me to conclude not to go anywhere near such an expensive installer who appears to be trying to sell everything and anything possible but find someone more reputable. Personally I would question using a NE face but others such as Martyn know far better than me. Also if you go with Solar Edge (which Martyn correctly questions as being the best way forward for you) then the information it produces is pretty good so I'd ask whether an Owl Monitor is really needed (I find it pretty easy to estimate how consumption against production is going without any such device).

pinnks

And if you go with the immerSUN as your diverter it has a monitoring option for £99 (or free via recommendation reward) and you can self-install if need be. I don't think any of the other diverters offer anything similar but may be wrong. Take a look at their website and navigate to the myimmerSUN page if you are interested to read up on what it offers...

EricMears

pinnks wrote: »

And if you go with the immerSUN as your diverter it has a monitoring option for £99 (or free via recommendation reward) and you can self-install if need be. I don't think any of the other diverters offer anything similar but may be wrong. Take a look at their website and navigate to the myimmerSUN page if you are interested to read up on what it offers...

I have this but have to say I'm not that impressed. The immediate display on computer screen is OK (albeit a bit flaky) but their idea of 'history' is to let me download 24 hourly results per day which is nowhere near enough to draw a decent graph.

Hemel_Saint

A Huge thanks to all the helpful info.
for a complete novice the jargon and tech info they use is mind-boggling.

I will come back with a few further comments / questions to the points you all make.
thanks again.
Mark

Hemel_Saint

tunnel wrote: »

In short

...Do you have any shading on any of the rooves?

The report states nil shading on both elevations.

However, do we really need the NE roof doing as well? ?
It is the NE roof that does impact the visual view of the house from the kerb, so not an issue to us if it was dropped from the scheme.
cheers
Mark

Hemel_Saint

Cardew wrote: »

Did they give any forecast of income/savings - with a breakdown?

Hi Cardew
Yes they did, for both sytems
a) 2 x rooves 6KWP
b) single roof 4KWP

kWh pa................... = a) 4494 ...b) 2996
FIT yr1 4.39........... = a) £198 ...b) £132
Power saving Yr 1... = a) £445 ...b) £297
Export Yr1 4.85....... = a) £87 .....b) £58
Total Benefit Yr1..... = a) £729 ...b) £487

hope the above formatting works!
thanks for your help looking into this for me.

cheers
Mark

tunnel

Hemel_Saint wrote: »

However, do we really need the NE roof doing as well? ?
It is the NE roof that does impact the visual view of the house from the kerb, so not an issue to us if it was dropped from the scheme.
cheers
Mark

If you don't want the NE then drop it. You can get higher Wp panels on the other roof to bring your total installed capacity up to 4kWp anyway, with no shading the one roof should come in at around £4k-£5k dependant on materials used.
Don't take any sh$t from the sales reps either, come on here and ask and you'll get some excellent advice.
If you post your rough location someone will help work out your expected returns plus you may get a recommendation or two for some installers if you're serious
T