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Solar Panels UK - is it worth it?
- Thread starter jdwuk
- Start date
we had ours fitted by some company that was a reasonable cost and they provided a free nest 3. They needed some handholding to get the opentherm part setup from the local fitter, despite their website talking about the benefits
- the risks of a national subbing out I guesswe had Tado and I still have their TRVs which I can use to report and limit temps in rooms - using the nest as a master controller
WannabeOwner
Well-Known Member
For O/P: It is likely to be worth fitting PV panels even on a North facing roof (if you have one), provided it isn't steeply sloping. One scaffolding erection/dismantle, overhead cost, visit by PV team, wiring, etc. so adding a second roof is nothing like 2x the cost. North will generate 75-80% of a South roof in Summer, and also has the benefit that it picks up early morning East and late evening West, before/after South will turn on/off, so contributes usefully early morning / later evening - when the house is likely to be consuming (but North will generate diddly squat in Winter - South is not a lot better!)
You can do a simulation for your roof (separately for each of roof-orientation / shape) using: pvwatts.nrel.gov/pvwatts.php
OK, that makes sense. I don't know the economics, but you could consider having the boiler heat hot water tank, and also fit immersion, and then only use boiler (to heat hot water) in Winter, in conjunction with central heating, and in Summer use a combination of PV-excess spilling over to immersion, and immersion on overnight Off peak rate.
My immersion comes on for the last hour or so of Off Peak (regardless of season) [to ensure we always wake up to hot water]. I haven't seen it come on in weeks (months??) because the hot water is heated sufficiently by Sun at this time of year. Immersion can be used (or Boiler to heat hot water tank) if you have a house full of people all wanting baths ...
Hopefully someone else can opine whether there is any financial sense in that route.
Pete UK
Member
OK, been running 3 weeks so far, so here is some data on the North facing panels (and whole system) as promised...
There are 27 panels in total; 420w Trina all black, Tigo optimisers on all. GivEnergy system: 2x 5.0 Gen3 hybrid inverters, 4x 9.5kW batteries.
Below is the N/S string of 5 South panels and 8 North panels, Then the East string of 8 on the higher roof + 6 on lower roof. N/S is a 45degree roof. East roof is 45 degrees or there abouts I think. Then the total generation for the day in the last picture.
This is on 7/7/23, the best day I've had so far generating 44.1kW - who wants to show their worst day, huh? But it is also the best day to show the difference in generation from different orientations. The average total generation I'm getting is 30kW a day for July so far.
On the N/S roof, the North kicks in much earlier in summer, then they swap over about 08:30, then at 11:30, the south array really lights up (mostly). With the East array, the lower 6 kick in a bit later in the morning as can be seen in the chart. This is due to the lower roof location/ shading from next doors house. (1st floor compared to the 8 on the second floor).
It's cloudy right now but I'm getting about 1400kW from the N/S and 1200 from the East arrays at 3pm. Todays peak was 7kW, the batteries were full at 10:20, the Model Y is full and i'm exporting. put 100kW in the car and exported 150kW so far in July.
These are the peak figures I've see at different times for each array so far; (not the average!)
N/S Inverter:
string 1: South (2299 max 1/7/23) - Equivalent to 5.47 panels (there are 5 panels on this string) - 109% of max panel rating
string 2: North (1925 max 1/7/23) - Equivalent to 4.58 panels (there are 8 panels on this string) - 57% of max panel rating
East Inverter:
string 1: 8 East Hi (3700 max 11/7) - Equivalent to 8.81 panels (there are 8 panels on this string) - 110% of max panel rating
string 2: 6 East Lo (2739 max 11/7) - Equivalent to 6.07 panels (there are 6 panels on this string) - 101% of max panel rating
Hope that is interesting to anyone looking at North facing panels. Cheers all !
There are 27 panels in total; 420w Trina all black, Tigo optimisers on all. GivEnergy system: 2x 5.0 Gen3 hybrid inverters, 4x 9.5kW batteries.
Below is the N/S string of 5 South panels and 8 North panels, Then the East string of 8 on the higher roof + 6 on lower roof. N/S is a 45degree roof. East roof is 45 degrees or there abouts I think. Then the total generation for the day in the last picture.
This is on 7/7/23, the best day I've had so far generating 44.1kW - who wants to show their worst day, huh? But it is also the best day to show the difference in generation from different orientations. The average total generation I'm getting is 30kW a day for July so far.
On the N/S roof, the North kicks in much earlier in summer, then they swap over about 08:30, then at 11:30, the south array really lights up (mostly). With the East array, the lower 6 kick in a bit later in the morning as can be seen in the chart. This is due to the lower roof location/ shading from next doors house. (1st floor compared to the 8 on the second floor).
It's cloudy right now but I'm getting about 1400kW from the N/S and 1200 from the East arrays at 3pm. Todays peak was 7kW, the batteries were full at 10:20, the Model Y is full and i'm exporting. put 100kW in the car and exported 150kW so far in July.
These are the peak figures I've see at different times for each array so far; (not the average!)
N/S Inverter:
string 1: South (2299 max 1/7/23) - Equivalent to 5.47 panels (there are 5 panels on this string) - 109% of max panel rating
string 2: North (1925 max 1/7/23) - Equivalent to 4.58 panels (there are 8 panels on this string) - 57% of max panel rating
East Inverter:
string 1: 8 East Hi (3700 max 11/7) - Equivalent to 8.81 panels (there are 8 panels on this string) - 110% of max panel rating
string 2: 6 East Lo (2739 max 11/7) - Equivalent to 6.07 panels (there are 6 panels on this string) - 101% of max panel rating
Hope that is interesting to anyone looking at North facing panels. Cheers all !
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where abouts are you located? I need to double check when I get back home to my home assistant but I think I was getting more from my north than my south, and my ratios are about the same as yours. South is 2.6kwp, north is 3.9kwp. Maybe age of array? South was installed back in 2011, or possibly clipping on the north as the installer put a 3kw inverter on that string..
Pete UK
Member
I've got a Chimney near my South array (and North come to think about it). How can you tell how much each string generates, apart from eyeballing the chart?
There is only data for each inverter, and the meter on each inverter. No idea how to see each string's generation individually. unless you add up all the generation snapshots (which I'm not doing !). Maybe Home assistant can do that for you then?
<------ Hertfordshire
Drew57
Active ember
A couple of weeks ago I added a further 2.2kW PV with four panels/microinverters on the SSW facing garage roof and one on the shed roof using a ballasted 'suntub' which has been initially aligned SE but can move in any direction SSW-SE (SE so it catches the sun earlier than the remaining panels which are all SSW). These panels generate separately from our remaining PV array which is registered to the FIT scheme and also charge the downstream house batteries via CT clamp from the Lux inverter.
The additional panels use a small Solis 2.5kWh inverter and the Zappi is now charging at 5.1kWh or greater in full sun, drawing from two inverters. The latest panels have an efficiency rating 21.3% and much better performance in low light conditions than the older (7y) PV array. With no need for scaffolding and 0% VAT this has added exactly what we needed for relatively minimal outlay.
On the sunniest days so far there have been periods of cloud and reduced output, nevertheless overall PV has generated up to 35kW per day and this is more than sufficient for the house, batteries, two EVs and two pensioners.
The additional panels use a small Solis 2.5kWh inverter and the Zappi is now charging at 5.1kWh or greater in full sun, drawing from two inverters. The latest panels have an efficiency rating 21.3% and much better performance in low light conditions than the older (7y) PV array. With no need for scaffolding and 0% VAT this has added exactly what we needed for relatively minimal outlay.
On the sunniest days so far there have been periods of cloud and reduced output, nevertheless overall PV has generated up to 35kW per day and this is more than sufficient for the house, batteries, two EVs and two pensioners.
- Solax X-Hybrid 3.6kWh inverter, 5.3kWh PV + 6.7kW batteries
- Solis 2.5kWh inverter, 2.2kWh PV...CT from Lux 3.6kWh inverter +9.6kW batteries
HA can do that - but I have two inverters so two separate arrays entirely which makes it a little easier. Although you’re limited to how good the software is. Eg I have no access to my original old south inverter software, but its clamped by both the zappi and the givenergy battery. The north array I have a fox inverter which lets me see generation, and its also clamped. Unfortunately the zappi sums any Solar CT clamps so I only get a total of both. but I can see the clamp power for each whihc can be used in HA to calculate energy over time, and I can also calculate using the Zappi total minus the fox one.
Not a simple thing and varies wildly depending on setup unfortunately.
got to wait until november for my FIT to be handed back to me - goign to cost £9k to buy the ‘leased roof’ out but its a 2011 scheme so I’m hoping for around £1700 a year index linked for another 13 years so should more than make that back.
I’ll have to stick with deemed export I guess as they won’t know if actual export is the second array or battery or whatever. I’m curious if I’ll be able to switch to SEG or other tariffs too - which would be my preference. Eg flux in summer.
I’ll have to stick with deemed export I guess as they won’t know if actual export is the second array or battery or whatever. I’m curious if I’ll be able to switch to SEG or other tariffs too - which would be my preference. Eg flux in summer.
Drew57
Active ember
You cannot have both FIT 50% deemed export and SEG at the same time.
FIT deemed export is great because it's theoretically possible to use everything you generate but still get paid for 50% of it as 'export' (as well as 100% for generation). We manage to use well over 50% of everything our system generates & frequently 100% so remaining on FIT is a no brainer especially as the scheme guarantees a minimum % increase in per kWh payment for each of the 25 years.
good point about the deemed if you self consume a lot. I was thinking about looking at higher paying SEG or Flux as deemed export isn’t a huge amount (although competitive with ‘normal’ SEG). But I’d need to monitor my grid export during summer especially to see if it’d be worth it vs deemed export (have to also estimate out my south array which is the FIT one)
Now that all the latest power tarrifs are out I've been back at the excel sheets checking that it is time to move to octopus IO (TL/DR - it is), but I was interested in the comparison between my current So.energy E7 tarrif, Octo IO and Octo Cozy. E7 gives us 00:00 to 07:00 at 22.7p (went up this month), IO gives 23:30 to -05:30 at 7.5p, and cosy is quite new, targeted at HeatPump users, and gives you 17.8p from 04:00-07:00 and 13:00-16:00. Downside is you are penalised to the tune of 47.47p per unit 16:00-19:00.
Doing the full year simulation of good days, average days and bad days for solar and linking in the HP usage, for my system I get:
so IO wins out both on cost and simplicity.
I mention Cosy however as it wouldn't take much to tip it over to winning out - if I could get a little more into my battery in those 2x3hr windows through the winter it would probably win out. Am now off to use the refferal link I have been given...
Doing the full year simulation of good days, average days and bad days for solar and linking in the HP usage, for my system I get:
so IO wins out both on cost and simplicity.
I mention Cosy however as it wouldn't take much to tip it over to winning out - if I could get a little more into my battery in those 2x3hr windows through the winter it would probably win out. Am now off to use the refferal link I have been given...
Pete UK
Member
This time of year? About 3.5kw per day to heat 300l of water to 55 deg C.
Shoulder seasons, from 6-20kw on heating.
Dec/Jan/Feb upto 30kw.
Slightly old stats I think actually - pre latest round of insulation, so hopefully better this coming winter. Once we aren't overgenerating solar I drop the HW back to 48 degrees, will see if a single tank of that is enough this winter with the added WWHR. 48 wasn't quite enough last winter and I would get complaints from the last person to shower
.This post has the data I'm using: Solar Panels UK - is it worth it?
Isn't there a risk of Legionella if you don't store your hot water at 60c? My Nest has a mode where if you don't get to 60c for two hours in the past 48 it'll override and heat it to kill the bacteria.This time of year? About 3.5kw per day to heat 300l of water to 55 deg C.
Shoulder seasons, from 6-20kw on heating.
Dec/Jan/Feb upto 30kw.
Slightly old stats I think actually - pre latest round of insulation, so hopefully better this coming winter. Once we aren't overgenerating solar I drop the HW back to 48 degrees, will see if a single tank of that is enough this winter with the added WWHR. 48 wasn't quite enough last winter and I would get complaints from the last person to shower
This post has the data I'm using: Solar Panels UK - is it worth it?
A risk, but vanishingly small as we use the full tank every day. It's also one of those speed to kill things, 60 degrees kills them in minutes, 55 kills them but slower. Combined with a solid turnover I'm happy with the temps we have. The HP by default has a once a week kill cycle, but given our usage I don't bother with it.
0 recorded infections from HP's in the UK.
I haven't checked this thread for a while so sorry if my comments don't go with the current flow. (no pun!)
Legionella - could be. Certainly been something to keep in mind. If you have thermal store, then it may heat cold water as you use it..... In which case no risk at all.
I'm battling with issues that will eventually effect most systems with batteries. How to decide when and how to upgrade.
Your batteries may not just die (although lithium subsystem batteries could die suddenly any time due to electronics failure). As (especially lead) batteries age and their characteristics change, the BMS / charger may start throwing intermittent errors. The batteries can still do useful work (and by this point in time are 'free', so the equation becomes hassle + reduced performance vs cost to replace. Lead (AGM) now has newer technology alternative (lead carbon) which is similar enough to be a drop-in replacement for AGM but has some especially useful characteristics for Solar PV (such as very happy to partial charge / discharge similar to lithium) but bulk and max DOD still not so good).
Lithium subsystems seem still quite tied to specific inverters, control interfaces and firmware versions. This is a potential hassle if you have a 10 year old hybrid inverter for which the matching lithium battery subsystem is no longer available.
There are quite a lot of lithium battery subsystems available now that claim compatibility with common inverters, but I'm not sure who would accept responsibility for ongoing performance and compatibility across firmware / hardware revisions.
For this reason alone I am leaning heavily towards having bms functions in the inverter / charger, or at least external BMS supplied by inverter manufacturer and 'simple' batteries of whatever technology you fancy.
If space isn't an issue, lead carbon looks well worth considering.
Regarding heating controls... I went with Drayton / Wiser mainly because you can turn off all external connectivity and the system still works and can be managed through local connection.
Ongoing support for kit in general is another concern I've been facing since one of my hybrid inverters was 'discontinued' and initially left with no software / app. Immersun (which has a slight link with Zappi) changed ownership a while ago and that felt quite precarious with regards to ongoing software provision. Small ticket item compared to solar PV but the principle is the same, as is the headlong rush into more and more Internet connected household systems that depend heavily on online systems to work.
Legionella - could be. Certainly been something to keep in mind. If you have thermal store, then it may heat cold water as you use it..... In which case no risk at all.
I'm battling with issues that will eventually effect most systems with batteries. How to decide when and how to upgrade.
Your batteries may not just die (although lithium subsystem batteries could die suddenly any time due to electronics failure). As (especially lead) batteries age and their characteristics change, the BMS / charger may start throwing intermittent errors. The batteries can still do useful work (and by this point in time are 'free', so the equation becomes hassle + reduced performance vs cost to replace. Lead (AGM) now has newer technology alternative (lead carbon) which is similar enough to be a drop-in replacement for AGM but has some especially useful characteristics for Solar PV (such as very happy to partial charge / discharge similar to lithium) but bulk and max DOD still not so good).
Lithium subsystems seem still quite tied to specific inverters, control interfaces and firmware versions. This is a potential hassle if you have a 10 year old hybrid inverter for which the matching lithium battery subsystem is no longer available.
There are quite a lot of lithium battery subsystems available now that claim compatibility with common inverters, but I'm not sure who would accept responsibility for ongoing performance and compatibility across firmware / hardware revisions.
For this reason alone I am leaning heavily towards having bms functions in the inverter / charger, or at least external BMS supplied by inverter manufacturer and 'simple' batteries of whatever technology you fancy.
If space isn't an issue, lead carbon looks well worth considering.
Regarding heating controls... I went with Drayton / Wiser mainly because you can turn off all external connectivity and the system still works and can be managed through local connection.
Ongoing support for kit in general is another concern I've been facing since one of my hybrid inverters was 'discontinued' and initially left with no software / app. Immersun (which has a slight link with Zappi) changed ownership a while ago and that felt quite precarious with regards to ongoing software provision. Small ticket item compared to solar PV but the principle is the same, as is the headlong rush into more and more Internet connected household systems that depend heavily on online systems to work.
Would rolling your own Victron controller be an option?
I feel like this isn't something we (as an internet using society) has really got to the bottom of yet. Since the early days I've learned not to trust anything that isn't absolutely core to Google to be around in their ecosystem more than a couple of years.
For my battery, I'm much more hopeful of Victron and its cloud app being around for the next 10 years than I am of PureDrive surviving, and the actual device has a local HTTP and MQQT interface if all else fails. We've already seen Andersen go pop, and its only that they were taken over by nice people rather than (say) British Gas means that the web interface is still running.
Your memory is too good! I am so fed up with batting my head against the DNO for permission to connect bigger than 7.6kw of grid-tie that I am seriously looking at off grid with minimal grid support. I am also working on an eco tourism project (100 x 450w panels) and also looking at some R&D into ways of simply engaging people with the energy activity in their homes. So, I can probably (certainly) repurposed the Victron. I agree that Victron has enough well established vertical markets that it has a track record for staying the course. For me the issue is that I'd prefer to quit being a pioneer cooking up ways to work around the system and start just being a mere beneficiary of someone else's diligence and integrity!
As my energy journey continues, I am moving towards a much simpler view.... Energy cost and timing in vs energy demand and timing. Since there is little reason to export 'energy', (you get paid a pittance for it) the trick is optimizing generation / capture, storage and control.
For me being grid-tied presents too many restrictions. I am working on a Victron solution for home and other projects, but the battery storage question is quite perplexing. Felicity seem to be trying to get a foothold with cheap batteries and long (claimed) wty including Victron compatibility, but LG Chem already left me feeling somewhat on my own with the Victron combination I have. Feels much more stable and understandable to have no more than solar PV input, one known brand inverter and some very basic batteries / cells possibly with grid charging. The interface between each module of that system is as simple as possible.
So now I am looking at paralleling up two or three inverters so they can deliver 20+ kW, maybe retain a single g98 grid tie, but probably not, and hook up a compleley separate battery charger (say 100A at 48v) so I can suck in off the grid if all else fails! I'd lose efficiency if ever I was running directly using grid power to DC then DC back to AC through the main inverter, but with no limits on kit from the DNO, I really think I could avoid using much if any grid power.
I suspect that least technical contact points between kit from different suppliers is a big plus, otherwise you might as well just accept that each purchase is only a known quantity until part of it packs up, and just go for the cheapest up front and buy spare kit if it makes you feel better.
For as long as batteries are expected to need replacement during system life expectancy, I'm leaning towards batteries needing to be as simple as possible. IE Just a group of cells.
As my energy journey continues, I am moving towards a much simpler view.... Energy cost and timing in vs energy demand and timing. Since there is little reason to export 'energy', (you get paid a pittance for it) the trick is optimizing generation / capture, storage and control.
For me being grid-tied presents too many restrictions. I am working on a Victron solution for home and other projects, but the battery storage question is quite perplexing. Felicity seem to be trying to get a foothold with cheap batteries and long (claimed) wty including Victron compatibility, but LG Chem already left me feeling somewhat on my own with the Victron combination I have. Feels much more stable and understandable to have no more than solar PV input, one known brand inverter and some very basic batteries / cells possibly with grid charging. The interface between each module of that system is as simple as possible.
So now I am looking at paralleling up two or three inverters so they can deliver 20+ kW, maybe retain a single g98 grid tie, but probably not, and hook up a compleley separate battery charger (say 100A at 48v) so I can suck in off the grid if all else fails! I'd lose efficiency if ever I was running directly using grid power to DC then DC back to AC through the main inverter, but with no limits on kit from the DNO, I really think I could avoid using much if any grid power.
I suspect that least technical contact points between kit from different suppliers is a big plus, otherwise you might as well just accept that each purchase is only a known quantity until part of it packs up, and just go for the cheapest up front and buy spare kit if it makes you feel better.
For as long as batteries are expected to need replacement during system life expectancy, I'm leaning towards batteries needing to be as simple as possible. IE Just a group of cells.
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WannabeOwner
Well-Known Member
I doubt it will stay that way - although it will for anyone exporting at periods of oversupply when "no one wants it" (even then grid-scale storage could mop it up "cheap" and export it later at "peak"). Exporting at times of high demand, from your home-battery/EV H2G, will be better (for grid operator) than firing up a peaker-plant - battery comes on stream much faster, so less need to rely on predicting excess-demand, and can scale - e.g. individual household battery systems could be requisitioned and/or AMPs defined (to match supply with demand). Battery doesn't have the ability to run for days/weeks though
which, in extremis, the peaker plants could.Still likely to have the situation where everything is full and you are exporting. Last year I magically managed to drive trips that used up the PV from the Sun that then shone - averaging about 70 miles a day through the summer. This year my mileage is way down and I'm exporting a lot more
It might be better than no one has a house battery, nor PV panels, and both of those are constructed at "grid scale" economy-of-scale, and folk just "buy from the grid". As grid-scale batteries become cheaper they will supplant peaker-plants (already happening in some places), they will also drive down the price of peak electricity as peaker-plant generation is replaced with battery-discharge, and maybe we wind up with a single price tarrif (which should be one that is more equitable than now, so long as supply-and-demand free-market is available)
Might be I'm having a pipe-dream though ...
