geographical information system tool results

FFHillbilly

I'm looking into solar panels on my roof, I've found a tool online that lets you estimate the yield depending on your location in the world (https://re.jrc.ec.europa.eu/pvg_tools/en/), but I'm not sure i'm doing it right the results seem a bit similar? the 2 graphs on the left are my two roofs, south east and north west, 31 degree slope
and the 2 on the right are due south and north for comparison. do these look right? I have enquired about getting panels on both sides of the roof and one installer said it would be pointless, the sun would never be there he said...
the way I see it is, in summer when I come home from work at 5pm, the sun would be on the NW roof for a few hours which would provide power for cooking evening meal.
and looking at the graphs, it still seems a decent bit of power from the NW roof?

Martyn1981

Hi, to help with advice, can I ask what the cost of the SE roof only would be, and then the cost of both roofs?

With PV, typically adding more at the smae time, costs proportionately less, and that's when using a less than ideal roof is worth considering.

For instance, if the generation from the NW roof is only 60-70% of that from the SE roof, but the additional cost is also 'only' 60-70% more, then the VFM is basically the same.

As you say, the NW roof will give you better generation in the late afternoon. Our WNW roof is now generating well till 6pm+, so let's say that's from May to August. And the late generation will, of course, only get later till the end of June, with good gen till 7pm+, and gen till around 9pm(ish).

You may also find that you won't need a much bigger inverter, as the two arrays won't peak at the same time. Our 5.58kWp system peaks at about 4.9kW in ideal circumstances, but can't hold that long (as panels get hot), so a sustained peak is about 4.2kW.

Grandad2b

There are a lot of variables to consider. If you're out all day then you are going to be timeshifting your generation. Depending on your usage a battery might make more sense than doubling the number of panels. Unfortunately I can't read the figures on your graphs. Your installer is right in a sense; the cost of the NW facing array will take much longer to pay back.
The tool you've found will give you a cost per kWh over the lifetime of your system - you just have to decide what works for you.

My roof faces slightly east of due south, output starts to drop off about 3pm at this time of year so I would expect you to have useable generation from a NW array at 5pm. 

paul991

Take into account the higher prices you get on flexible tarriffs from octopus ect peak rate from 4 to 7 pm

FFHillbilly

Martyn1981 said:

Hi, to help with advice, can I ask what the cost of the SE roof only would be, and then the cost of both roofs?
Haven't got that far, all the quotes I've got are different specs but I am exploring the possibility of buying it all myself and panels are £180 each, brackets & fixings not much extra, and scaffold could probably be ignored because I am looking at replacing the roof tiles anyway as they are 50 years old

Grandad2b said:

 Depending on your usage a battery might make more sense than doubling the number of panels. Unfortunately I can't read the figures on your graphs. Your installer is right in a sense; the cost of the NW facing array will take much longer to pay back.
I'll probably be getting a battery, well I'm leaning towards one anyway. and possibly even installing an indirect unvented water cylinder, which I could divert excess generation into using a PV diverter
I know you might be thinking thats a crazy idea to install one of them just to be able to use more generation, but I currently have a 18 year old combi which has started showing signs of breaking and realistically within 2 y years it'll need replaced, and I also hate the combi boiler wastage and slow response, I seem to have to run off 20 litres and have to wait 30-40 seconds to get hot water out of my kitchen sink.
I have also been reading the "solar diverter slagging thread" on here and it seems most are against them being used in favour of cheap gas If I have the option, but looking long term I can see them coming back into play as soon as the "green taxes" get shifted from electricity to gas 

paul991 said:

Take into account the higher prices you get on flexible tarriffs from octopus ect peak rate from 4 to 7 pm
do you mean, I could export any generated energy (i.e Flux) at this peak rate, meaning the extra panels on the NW roof might not gather as much power, but the time at which they gather it means it's more valuable?

replies above in bold

Grandad2b

FFHillbilly said:

Martyn1981 said:

Hi, to help with advice, can I ask what the cost of the SE roof only would be, and then the cost of both roofs?
Haven't got that far, all the quotes I've got are different specs but I am exploring the possibility of buying it all myself and panels are £180 each, brackets & fixings not much extra, and scaffold could probably be ignored because I am looking at replacing the roof tiles anyway as they are 50 years old

Grandad2b said:

 Depending on your usage a battery might make more sense than doubling the number of panels. Unfortunately I can't read the figures on your graphs. Your installer is right in a sense; the cost of the NW facing array will take much longer to pay back.
I'll probably be getting a battery, well I'm leaning towards one anyway. and possibly even installing an indirect unvented water cylinder, which I could divert excess generation into using a PV diverter
I know you might be thinking thats a crazy idea to install one of them just to be able to use more generation, but I currently have a 18 year old combi which has started showing signs of breaking and realistically within 2 y years it'll need replaced, and I also hate the combi boiler wastage and slow response, I seem to have to run off 20 litres and have to wait 30-40 seconds to get hot water out of my kitchen sink.
I have also been reading the "solar diverter slagging thread" on here and it seems most are against them being used in favour of cheap gas If I have the option, but looking long term I can see them coming back into play as soon as the "green taxes" get shifted from electricity to gas 

paul991 said:

Take into account the higher prices you get on flexible tarriffs from octopus ect peak rate from 4 to 7 pm
do you mean, I could export any generated energy (i.e Flux) at this peak rate, meaning the extra panels on the NW roof might not gather as much power, but the time at which they gather it means it's more valuable?

replies above in bold

It might be difficult to follow the thread if your replies look to the software like they're previous quotes...

If you can install the system yourself and get MCS sign off that would clearly be a great way to save on installation cost. Against that you'd have just the manufacturers' warranty... Without MCS sign off your prospects of getting paid for export are slim to non-existent.
Your combi has done well to last 18 years. In the 18 years I've lived here one neighbour has had 2 combis. Meanwhile our ancient gloworm keeps plodding along. It's not efficient but it's certainly moneysaving. The 30 second wait for hot water is the same though since the cylinder is next to the bathroom rather than the kitchen. I think if I was starting from scratch I'd be looking to see if local instant water heaters made sense. Would definitely need a battery for that.

FFHillbilly

Grandad2b said:

FFHillbilly said:

Martyn1981 said:

Hi, to help with advice, can I ask what the cost of the SE roof only would be, and then the cost of both roofs?
Haven't got that far, all the quotes I've got are different specs but I am exploring the possibility of buying it all myself and panels are £180 each, brackets & fixings not much extra, and scaffold could probably be ignored because I am looking at replacing the roof tiles anyway as they are 50 years old

Grandad2b said:

 Depending on your usage a battery might make more sense than doubling the number of panels. Unfortunately I can't read the figures on your graphs. Your installer is right in a sense; the cost of the NW facing array will take much longer to pay back.
I'll probably be getting a battery, well I'm leaning towards one anyway. and possibly even installing an indirect unvented water cylinder, which I could divert excess generation into using a PV diverter
I know you might be thinking thats a crazy idea to install one of them just to be able to use more generation, but I currently have a 18 year old combi which has started showing signs of breaking and realistically within 2 y years it'll need replaced, and I also hate the combi boiler wastage and slow response, I seem to have to run off 20 litres and have to wait 30-40 seconds to get hot water out of my kitchen sink.
I have also been reading the "solar diverter slagging thread" on here and it seems most are against them being used in favour of cheap gas If I have the option, but looking long term I can see them coming back into play as soon as the "green taxes" get shifted from electricity to gas 

paul991 said:

Take into account the higher prices you get on flexible tarriffs from octopus ect peak rate from 4 to 7 pm
do you mean, I could export any generated energy (i.e Flux) at this peak rate, meaning the extra panels on the NW roof might not gather as much power, but the time at which they gather it means it's more valuable?

replies above in bold

It might be difficult to follow the thread if your replies look to the software like they're previous quotes...

If you can install the system yourself and get MCS sign off that would clearly be a great way to save on installation cost. Against that you'd have just the manufacturers' warranty... Without MCS sign off your prospects of getting paid for export are slim to non-existent.
Your combi has done well to last 18 years. In the 18 years I've lived here one neighbour has had 2 combis. Meanwhile our ancient gloworm keeps plodding along. It's not efficient but it's certainly moneysaving. The 30 second wait for hot water is the same though since the cylinder is next to the bathroom rather than the kitchen. I think if I was starting from scratch I'd be looking to see if local instant water heaters made sense. Would definitely need a battery for that.

well I agree about the post being hard to read but unfortunately I'm unable to change that now it just seems impossible 
the idea of installing myself it probably a not starter too, for one I don't think the quotes I'm getting are that bad, and I've also realised that I would be liable for the 20% VAT if I bought the kit myself. and even if I could get the VAT back, the export tariff (or lack of) for a DIY install would make it less appealing.
when I originally thought up the idea I had no intention of exporting a single kwhr, but octopus flux has has changed my mind

paul991

FFHillbilly said:

Martyn1981 said:

Hi, to help with advice, can I ask what the cost of the SE roof only would be, and then the cost of both roofs?
Haven't got that far, all the quotes I've got are different specs but I am exploring the possibility of buying it all myself and panels are £180 each, brackets & fixings not much extra, and scaffold could probably be ignored because I am looking at replacing the roof tiles anyway as they are 50 years old

Grandad2b said:

 Depending on your usage a battery might make more sense than doubling the number of panels. Unfortunately I can't read the figures on your graphs. Your installer is right in a sense; the cost of the NW facing array will take much longer to pay back.
I'll probably be getting a battery, well I'm leaning towards one anyway. and possibly even installing an indirect unvented water cylinder, which I could divert excess generation into using a PV diverter
I know you might be thinking thats a crazy idea to install one of them just to be able to use more generation, but I currently have a 18 year old combi which has started showing signs of breaking and realistically within 2 y years it'll need replaced, and I also hate the combi boiler wastage and slow response, I seem to have to run off 20 litres and have to wait 30-40 seconds to get hot water out of my kitchen sink.
I have also been reading the "solar diverter slagging thread" on here and it seems most are against them being used in favour of cheap gas If I have the option, but looking long term I can see them coming back into play as soon as the "green taxes" get shifted from electricity to gas 

paul991 said:

Take into account the higher prices you get on flexible tarriffs from octopus ect peak rate from 4 to 7 pm
do you mean, I could export any generated energy (i.e Flux) at this peak rate, meaning the extra panels on the NW roof might not gather as much power, but the time at which they gather it means it's more valuable?

replies above in bold

yes its worth looking at the rates available on flux .I think more TOU tarriffs will become the norm  my roof is 240 degrees and gives  a good return i have thought it might be worth having a panel on the back to pick up some early morning  sun 

BossBob

Given the number of mornings that I get early morning sunshine followed by cloud I’ve also wondered why I don’t have some panels on my NE facing roof!

Martyn1981

FFHillbilly said:

Martyn1981 said:

Hi, to help with advice, can I ask what the cost of the SE roof only would be, and then the cost of both roofs?
Haven't got that far, all the quotes I've got are different specs but I am exploring the possibility of buying it all myself and panels are £180 each, brackets & fixings not much extra, and scaffold could probably be ignored because I am looking at replacing the roof tiles anyway as they are 50 years old

replies above in bold

Thanks, and reading other comments I see you are thinking about having it installed, rather than doing the work yourself. So, definitely worth you getting a SE quote and a SE + NW quote. I suspect the cost of the extra will be proportionately less, so may make up for the lower annual generation. If that's the case, and you can afford the extra, then the cost per kWh of generation should be the same (if that makes sense), and you get the evening bonus in the summer (I'm being lazy and simply splitting the year into winter and summer).

For a winter boost, the NW will be poor, as your PVGIS results show, and a lot of the extra gen (in the summer) may be export, as the SE may be generating a lot already. Of course, that's when export tariffs and batts kick in, giving you lots to think about. Personally, so long as the extra is cost effective, then I'd definitely want extra generation, and some future proofing.


Silly bit now, but something has been bugging me, and this really isn't that important, but worth checking - and that's your NW 'best v's worst' generation. Looks to me that June is 20.5x more than Dec (418 v's 20.21). That seems extreme, my 30d pitch WNW is ~11x, and using my location but 31d pitch instead of 30d, and changing from azimuth 105d to 135d I get ~15x.

That could of course be down to location in the UK, but I also noticed that your N figures are fractionally 'better' with a ratio of 19.4x ..... so just wondering if the NW entries are correct, or if a small anomaly/error has been entered? But I doubt this will be significant enough to change anything? [All my entries are just using the default settings, I only enter 1 in the kWp box, and the slope and azimuth, so you may have added additional info that personalises it more.]

FFHillbilly

Martyn1981 said:

FFHillbilly said:

Martyn1981 said:

Hi, to help with advice, can I ask what the cost of the SE roof only would be, and then the cost of both roofs?
Haven't got that far, all the quotes I've got are different specs but I am exploring the possibility of buying it all myself and panels are £180 each, brackets & fixings not much extra, and scaffold could probably be ignored because I am looking at replacing the roof tiles anyway as they are 50 years old

replies above in bold

Silly bit now, but something has been bugging me, and this really isn't that important, but worth checking - and that's your NW 'best v's worst' generation. Looks to me that June is 20.5x more than Dec (418 v's 20.21). That seems extreme, my 30d pitch WNW is ~11x, and using my location but 31d pitch instead of 30d, and changing from azimuth 105d to 135d I get ~15x.

Good point, I've double checked all my figures and they are correct, all I'm inputting is 4kwp , roof mounted, 31 degree slope and 135(NE) and 45(SE). just to check the numbers I put in for N & S were 180 and 0.
(I've tried it with 1kwp, I still get the same difference between best & worst)
Maybe thats as good as we get in winter up north? as in the real north, not just past Birmingham!
I've got the favourite quote so far to fiddle round with them a bit, I've asked for a quote for panels on both sides, 5kw hybrid inverter, 4.8kwhr batteries. 
and then a separate quote for just panels on one side
I think then I will be able to "make an educated guess" as to whether or not it would be worth doing