Solar system in Oxon/Wilts

marcus_h

Dear MoneySavers

I am getting closer to taking the PV plunge. I’ve enclosed a pic of the house orientation.



- The roof is 9m at the base (indicated by red line) and 5m at the top.
- The pic is oriented so that North is straight up – so the house is S-SE.
- There is quite a bit of sun on the Western exposure, but we have an extension in mind for there, so unsure whether it would be good to situate any panels there.
- There is a laundry room (originally a lean-to) on the west side, which would be a good location for the inverter, I was thinking.

I am on the south Oxon/Wilts borders. I would take out a loan, but at 3.7% interest, the numbers don’t seem too bad. It is an all electric house.

Questions then:
- looking at the JRC site, I am estimating an azimuth of -30. Does that look right?
- the numbers for the year (E and H) based on 4kw system are 3800 and 1230
- what does that actually mean in terms of my costs etc?
- any recommendations of a solar fitter nearby?

Seems to me we are in a good place for solar, but any help from Martyn1981 or any of the other solar gurus in identifying anything I need to consider would be much appreciated!

Martyn1981

Hello Marcus. Welcome to the PV madhouse.

Location is fine, if I got it right? I stuck a pin in Pangbourne, just for an estimate on the PVGIS site.

-30 looks about right, and I left the roof pitch default at 35d (yours might be steeper, perhaps 40d not sure). The result for 4kWp was 3,840, so that sits well with your estimate.

Not sure how much you could fit on that roof, it will depend on how tall it is. But 9m at the base would suggest perhaps 7 panels portrait, then another 4 on top, so 11 panels if room for 3.2m high. If the roof will allow 3 rows of panels, so about 5.5m to allow 4.8m of panels, then 16 panels should fit.

Hipped rooves are hard to work out, but I'd suspect that some combination of panels, perhaps landscape, or higher efficiency panels, will get you up to the 4kWp mark.

The WSW roof looks good too, but again, hipped rooves are tricky, and squeezing 1.6m by 1m objects on to that roof might mean you can't get many on. You'd probably also want to consider some sort of shade mitigation, as the property to your west might cause a fair bit of shading in the GMT months.

If you can get 3+kWp on the SSE, and might be playing around with the WSW (extension) then maybe best not to do that side.

Loans and PV aren't great ideas, but 3.7% doesn't sound bad at all, and if you are all electric then your savings will be higher than most. Also if you get a diverter to heat your water, to try to maximise use of generation, and minimise import for water heating, then savings will be greater again.

Not sure I can give an accurate guess for leccy savings, hopefully someone else will have an idea, but I'd suspect it would be around £200 or more ...... really not sure.

Mart.

marcus_h

Thanks Martyn. I think you are right on the West facing roof. I hadn't really though about it until I looked at that satellite image, and saw it in full sunshine. I haven't monitored the potential shading, and in winter, it would be quite a bit like you say.

So I could calculate something like £490 for generation, maybe £200 savings, and then a certain amount for export on top correct?

A £5500 loan at 3.7% will work out at about £6000 including interest. So the approximate numbers look OK, I think. A 0% CC would be better again though

Martyn1981

Hi Marcus. Yep, £490 FiT and £92 export (1,900 @ 4.85p (50% deemed export)).

Do you have a hot water tank, or instantaneous water heating? Also, are you currently on E7? Your leccy savings should be higher than a 'normal' (sorry!) house, but still hard to calculate, depending on your circumstances. How much do you import each year, how much on the day rate if you have E7?

The shading on the WSW will be quite high, but not a killer. I've got a friend whose whole SW 3kWp system is on the side of the house, as their rooves run front to back. His neighbour is only 3 feet away, and has a pine end roof, so a bit like you, only closer and a vertical roof/wall next door. He doesn't have any shade mitigation as it was installed in late 2010, and his generation in the poorer months is terrible due to shade, but he still gets 2,500 kWh per year.

I'd ignore that roof, purely because you said you might make changes in the future. If not, then I'd use it, subject to getting enough panels on there, just to improve the generation curve through the day. But then you'd need something like a Solaredge system for shading.

I don't want to be cavalier about it, but if your income is in the £700+ range, then a low rate loan on an install of less than £6k (fingers crossed for nearer to £5k) would work out fine, so long as you know what you're doing.

As per your first post, you just need some quotes and recommendations now, to get the ball rolling. Don't rush, but be aware that the FiT rate drops to 12.47p on 1/10/15. If you can beat that then fine, but overall it's only an income drop of about 2%, so don't rush if taking your time would get you a 2% better price.

Mart.

marcus_h

Thanks Martyn

Definitely will be sourcing a few quotes soon

In terms of use, we have an immersion hot water tank. We used 7419/972/6000 (storage/night/day) over a year (June to June).

Our current tariff is quite high, but only recently had our meters changed over (from accompanied, I think it was, to a standard set up) so we can change to a better supplier. They have been 7.82/9.32/17.61, respectively. Always seems quite alarming!

So any recommendations for a fitter would be good too!

michaels

For prices, we had ours in St Albans done at the end of June for 4800 all in including an iboost immersion diverter for 4800 (2 aspect, solar edge, 16x250 panels) from TP Solar in Wellingborough. I think there is a referral scheme which I would be happy to split with you if you choose to get a quote from them (PM me). WE have about 5m from gutter to ridge and were able to fit 3 rows in vertical orientation so if you have this much then you will easily fit 2 rows of 5 and one of 6 or normally the 285w panels requiring only 14 altogether are normally a similar price.

Martyn1981

marcus_h wrote: »

In terms of use, we have an immersion hot water tank. We used 7419/972/6000 (storage/night/day) over a year (June to June).

Our current tariff is quite high, but only recently had our meters changed over (from accompanied, I think it was, to a standard set up) so we can change to a better supplier. They have been 7.82/9.32/17.61, respectively. Always seems quite alarming!

Ok, that's interesting. So you have high daytime consumption, so that should mean higher leccy savings. Also you have an immersion*, so all PV diversion will be saving you money at leccy prices (not gas prices), however I assume the water heating is set for night (or does it come under storage?), so savings at 9.32p/kWh, so if you manage to divert say another 1,000kWh pa, then that'll mean an extra £93 (at least).

[Edit: *Should have said, diversion is not automatic, you will need to have a diversionary switch installed, this will probably add around £200 to the cost. M.]

I'm still guessing, and trying hard not to mislead you, but I think it's now fair to say that your leccy savings will be more than £200 pa.

Mart.

marcus_h

micheals, Martyn - thanks for those points.

Martyn - that sounds good news. My OH and I do work a lot from home, so the solar should be good. I think the water comes under storage, rather than night, as the night usage is low. These rates are due to change soon, when I get a better deal.

micheals - that is a great deal. I looked at their site, and it seems to look more like £5500. Did you negotiate hard? How good are the Solar Edge panels?

pinnks

Marcus_h

I probably don't live that far from you in North East Wilts. I used eco2solar in Kidderminster as they came recommended from a friend in the midlands. I am pleased with their workmanship, sales approach etc. No pressure selling, one-off discounts and that sort of rubbish, just good advice and leave you decide whether and if so when to go with them. Indeed, I used them for my second system too.

As you have an all electric house and immersion heater I assume you will be considering a diverter. I opted for the immerSUN. First it can power 3 resistive load outputs. So, as an all electric house you could get some space heating in spring and autumn by attaching storage heaters, oil-filled rads or similar to the additional outputs. Once the water is hot in the immersion, output 2 cuts in. When output 2 is "hot" output 3 cuts in and then back to output 1. If the immersion needs more heat it take priority over the other outputs even if they are not hot etc. You can also programme on and off times for each output so use it as a normal heating control timer, though I have not really looked at that option as it is of no interest/use to me. Their myimmerSUN monitoring product is also good but adds £99 to your install.

If you system is big enough (only really relevant for systems over 4kWp) you can cascade up to 4 more immerSUNs so that if you are producing more that the first immerSUN can utilise (max 3kW load on each output and each output works sequentially) the rest is diverted to unit 2 with its 3 outputs and so on. I have 5.25kWp and have invested in a second immerSUN to power some radiators in spring and autumn. I could have done this using outputs 2 and 3 on the first immerSUN but that would have meant running cables, some of which would have been visible which I did not want, so I use output 1 for the immersion and output 2 for a radiator in my home office on the original immerSUN and then the other immerSUN to power 2 2400W oil-filled radiators. Works well for me.

I don't think the other diverters can do this but you might want to check the details of each before making your choice.

michaels

marcus_h wrote: »

micheals, Martyn - thanks for those points.

Martyn - that sounds good news. My OH and I do work a lot from home, so the solar should be good. I think the water comes under storage, rather than night, as the night usage is low. These rates are due to change soon, when I get a better deal.

micheals - that is a great deal. I looked at their site, and it seems to look more like £5500. Did you negotiate hard? How good are the Solar Edge panels?

When I got mine their 'cheapest' advertised price was 4850 but the estimator basically implied they would throw in an iBoost at that price as 'negotiation'. Then when the installers arrived they found they couldn't fit 4 panels on one of the aspects which meant that a 2 string inverter (sma sunny boy) would not work so ended up installing the panels with the built in solar edge optimizers and the solar edge inverter and didn't try and increase the price which makes them good guys imho

Whether they are still willing to get anywhere near that price I don't know. AS you only have one aspect I would have thought it should be OK as you can go for bog standard (and therefore cheap) panels and inverter although the conservatory might be a slight issue for the scaffolding.

I don't know if there has been any discussion / calcs over the relative advantages of higher quality panels and inverters than may produce a few percent more power every year for 20 years compared to the extra price of the initial install, presumably it wouldn't be hard to model in excel.

marcus_h

Thanks both. I will get TP and eco2solar to give me a quote. From what Pinnks says, the immerSUN is a bit more flexible than the iBoost, which TP don't do. But if I got the whole thing @ 4800, I wouldn't complain.