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Solar PV – Frequently Asked Questions and Answers

edited 28 August 2019 at 6:51AM in Green & Ethical MoneySaving
109 replies 76K views
Martyn1981Martyn1981 Forumite
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edited 28 August 2019 at 6:51AM in Green & Ethical MoneySaving
Solar PV Q&A's Index PTI

The following is a list of general topics and questions that regularly get asked on the various MSE solar PV threads. All of the advice comes from enthusiastic PV owners. It should not therefore be considered technically perfect, nor 100% accurate. It should only be considered as shared advice and experiences.
Also please note, there is no such thing as a simple question (nor a simple answer), this post is only meant as a first port-of-call, you will always learn more by chatting on an appropriate thread and gaining additional input and opinions.

1. I'm only thinking about getting PV - What should I consider?

2. I want to get PV installed - How do I go about it / What should I do next?

3. Now I have PV - How do I get the most out of it?

4. My meter is running backwards - Do I need to do anything?
4a Meters reading export as import
4b 3 phase meters
4c Smart meters

5. Estimating generation - How do I estimate my monthly/annual generation or check that my system is performing correctly?

Sections 6 onwards are found in post #37 (click on the white chevron in the link below):
Martyn1981 wrote: »
Solar PV Q&A's Index PTII


6. Energy monitors - How do they work / Should I get one?

7. I've had PV installed !!!8211; But what exactly are all the parts called / What do they do?

8. Getting serious with circuits - some DIY ideas for the less technically challenged.

9. Feed-in-Tariff registration and changing suppliers

10. Adding to an existing PV system, or adding an additional PV system at the same address.

11. Common terms and acronyms used on this site in conjunction with PV and renewables in general.

12. FiT Degressions

13. Basic consumer advice and protection.

14. Inverter shutting down, reporting overvoltage / Grid voltage too high.

Please point out any posts that you think it would be helpful to add to a particular subject, or any additional subjects that could be added to the list.
Thank you.


1. I'm only thinking about getting PV - What should I consider?

Spend some time researching PV on the internet.

The main MSE site gives information here:

Solar Panels: Should you buy or get them free?

The Energy Savings Trust website gives information here:

http://www.energysavingtrust.org.uk/Generate-your-own-energy/Solar-panels-PV

The Solar Trade Association has created an advice site called 'YourRoof' giving broad information here:

http://yourroof.info/powerFromYourRoof.cfm

Try speaking to somebody nearby who has had an install, hopefully they will be happy to explain what is needed and their experiences.

An ideal roof will be South facing. The further from South that the roof orientation is, the less efficient it will be. South East and South West roofs will generate about 10% less than South. East and West roofs will generate about 20% less than South.

[Note - The economics of PV, especially with the large amount of fixed costs (scaffolding, internal work, inverter etc) mean that as the size of the install goes up, the costs won't rise proportionally. This may mean that installing additional panels on non south roofs may be beneficial. It is not easy to explain this in brief, however it is discussed and explained in detail on a thread which looked to find the most economic solution to a property with the option of using up to three rooves:

Solar PV Quote seems excessive


Shading can have a large impact on generation, especially during Winter months when the sun is lower in the sky. Consider neighbouring structures and trees.

Savings and income: There are 3 sources and they are all tax free:-

1. THE FEED IN TARIFF HAS NOW ENDED. The Feed in Tariff currently (from 1/10/18) pays 3.86p per unit (kWh) generated for installs that are 0-10kWp. This amount is index-linked and runs for 20 years.

The rates will then be reduced each qtr as per this OFGEM document. However, there are strict MWp install limits, and once reached, any install will be queued up (in order) and receive the later (and lower) tariff appropriate to the qtr it gets registered in. Any capacity not taken up gets rolled forward.

2. THE EXPORT TARIFF HAS NOW ENDED - however rules are being formulated to ensure that electricity suppliers offer a payment for export, but this will need to be researched.

The export tariff pays for exported units, 5.24p/kWh. For most installs this will not be accurately measured, instead it will simply be estimated/deemed at 50% of generation.

information on FITs and the export rate can be found at

http://www.decc.gov.uk/en/content/cms/meeting_energy/renewable_ener/feedin_tariff/fits_faqs/fits_faqs.aspx

The FiTs subsidy and export payments scheme is to end 31st Mch 2019, and there is not currently any planned replacement, for either, for installs after that date.

3. Savings on your electricity bill. Consuming electricity that is being generated by the PV at that specific time, will save you importing as much electricity from your energy supplier. The amount of savings will depend on the size of the PV system installed, how much electricity you use, and importantly, whether there is much electrical consumption during the working day, when the PV is generating. Savings will vary from household to household, but could be approx. £120 (probably in the £80 to £160 range). Larger savings are possible, but will require higher daytime consumption.

3. (cont) Beware quotes that give overly optimistic levels of savings, higher savings are difficult (for most) and require increasing effort. Also, for electricity customers who pay via a two tier tariff scheme, PV will be reducing consumption 'off the top' so estimated savings should be based on lower tier 2 prices, not higher tier 1 prices (refer to your charges). Similarly, some quotes project enormous savings in the future via compounding large annual bill increases for the whole 20 years. Do not be misled, future prices remain an unknown, for decision purposes only expect reasonable annual savings. Ask PV'ers for their experiences.

Many Pv'ers are reporting a 4th source of income/savings. They have found that a better awareness of electrical generation and consumption, has led to a small reduction in demand, regardless of how conscientious they thought they were before installing PV.

Maintenance and upkeep: Solar PV needs little maintenance - you'll just need to keep the panels relatively clean and make sure trees don't begin to overshadow them. The panels should last 25 years or more (hopefully 40+), but the inverter is likely to need replacing some time during this period, at a current cost of around £600 to £1,000.

There should be no change to your buildings insurance, but check with your insurer, and notify them of the PV install.

To qualify for the higher rate of FITs, you will need to obtain an Energy Performance Certificate of D or better on your property, towards which the PV itself can contribute. For more information see the DECC website above.

You can't move your install if you move. So it's important to consider and compare the lengthy pay back period of the PV alongside your long term plans to remain in the property. Whilst the FITs income will remain with the property for the full 20 year period, this doesn't mean that any prospective buyer will necessarily want, value nor appreciate the PV system. There is simply no way to guess what the effect of a PV system will have on the final price of your property, it will depend entirely on the buyer in question.

If you are thinking about investigating PV further, then take a look at item 2 on the index.


2. I want to get PV installed - How do I go about it / What should I do next?

Here's a tip sheet

http://www.which.co.uk/documents/pdf/solar-pv-checklist-pdf-269629.pdf

If possible have a good chat with someone that already has PV. Ideally, speak to a neighbour / someone nearby. Most PV'ers will probably be happy to have a chat and show you all the bits and bobs.

Get as many quotes as you feel comfortable with (2 minimum). Ask for company recommendations from friends, neighbours or individuals on sites such as this. However, beware any individuals that may be salespersons in disguise!

For each visit get a written quote that sets out everything that is included, and ask if there is anything that is not included. If you are at all unsure, then use sites such as this, or technical forums to ask for opinions on the system (such as specific panels and inverters). Keep coming back to us for some 'crowd' thinking.

If you are reasonably confident about the size of your roof, and the panel numbers, and orientation that is possible, then you may find it useful to standardize your quotes by asking for a specific system size e.g. 3kWp, and a preferred inverter option (if you have one). But do still ask each representative for their thoughts and suggestions.

To get a more accurate estimate of the potential generation of your proposed install, try using PVGIS to get a better guess at generation. See index item 5 for more information.

*IMPORTANT* Ask on this forum (or others) for opinions on the price of the install before committing, if you are at all unsure. Prices are in dramatic flux at the moment.

Try not to rush, or be rushed. Take your time and do your research.

Some recent MSE threads:

Solar PV...Still worth it?


3. Now I have PV - How do I get the most out of it?

Rule 1, don't get too obsessed, if it's not fun, then you're trying too hard!

Rule 2, this issue sits within the question "how long is a piece of string?". There is no short answer, you will need to monitor threads, and chat with fellow PV!!!8217;ers, exchanging hints, tips and ideas. The following is no more than a very short summary to get you started.

To save money on your electricity bill from PV, then you will need to use the electricity being generated rather than importing it from the grid. Whenever PV is generating it will contribute to your consumption as the household demand will always use PV first before calling on the grid for any shortfall.

PV will contribute to (or cover at higher generation) baseload (fridge, freezer, clocks, answerphones, standby's, etc) without you making any particular effort.

The next step is to try to run items when generation is higher (the sun is higher or cloud cover is less), this can be achieved more simply if the house is in use during the day, if not, then through the use of timer switches, or programmes on many appliances.

Staggering items can allow you to consume more generation over a longer period. E.g. running 4 large items for an hour may mean that generation only contributes some of the demand, for that 1 hour. Running them separately for an hour each, would allow generation to contribute to the lower demand (at any given time) for the whole 4 hours.

Some PV'ers attempt to maximise use of generation (and minimise export of excess) via heating of stored hot water. This will only be possible if your house has a suitable system with an immersion heater. However, this is not easy to achieve and if miscalculated could lead to increased costs e.g. if Gas costs approx 5p/kWh and 'imported' electricity approx 15p/kWh, then if the immersion heater is using 1kW of imported electricity and 2kW of PV electricity, the cost is the same as using 3kW of gas.

Heating of water is discussed here

Choice of intelligent switches ?

and a discussion for competent DIY'ers here:

device to use unused soler pv export power to run heater or hot water

Some recent MSE threads:

So now I have a solar PV system how do I make the most of it???


4. My meter is running backwards - Do I need to do anything?

If your import meter is running backwards, then at some point the meter will need replacing, and the household should expect to have to pay for the imported units that they haven't paid for as they were 'deleted' by exported (backwards) units. Those exported units are already being paid for via FITs at 3.3p (install before 1/8/12) or 4.91p (install after 1/8/12) on an assumed 50% export of generation. Running a meter backwards means that they are being paid for a second time by deleting full price units.

Usually, when applying to your supplier for FITs registration, one of the questions is 'does your meter go backwards'. If you have one of the old-style meters which will run backwards you should answer 'yes'. If the question is not asked in the application form, it is prudent to let them know, otherwise there is likely to be a bill for the assumed extra owing the company when they do find out.

Do not be overly concerned, this is a common issue, but it will need to be resolved. A new meter should normally be supplied FOC.

Some recent MSE threads:

shoudl meter go backwards or stay still?

4a Meters reading export as import:

Though rare, some people have found that their import meter may be reading the excess electricity that is being generated and exported to the network as if it is being imported.

This appears to be a known 'fault' with some Siemens meters (possibly S2AS) that have an 'anti-tamper' programme. All the exported units are supposed to be available from an internal register - though you may have difficulty in finding an operator who understands the situation. Your REC's solar energy helpline might be able to help.

Some recent MSE threads:

Siemans S2A meter - I think there maybe a problem

Electricity (grid) meter incorrect


4b 3 Phase meters

Potential problem with 3 phase meters, such Landis&Gyr (also Ampy) 5219 and an Itron ACE3000-520. Export is always treated as zero when it comes to incrementing the meter. So if your exporting say 10kW in total on two of the phases but importing 3kW on the other it is increasing the meter by 3kw when it shouldn't be increasing at all.

These meters are configurable and need to be configured correctly for PV.

(for more info see post#66 tinbum1 23/7/14 on this thread.)

4c Smart meters

Currently there is no clear picture regarding smart meters. It's possible that the smart meter will monitor export and export payments will be based on this, or that it will monitor export, but export payments won't be based on it, or that the smart meter won't monitor export at all.

There is also the issue that if your electricity supplier is different to your FiT supplier, then they might not be willing to use the technology, they may have different types/generations of smart meter etc.

As there is no clear answer, it's best to contact your FiT provider and ask them for clarification on the matter, and perhaps any indications regarding future policy, though this may well be even less clear.


5. Estimating generation !!!8211; How do I estimate my monthly/annual generation or check that my system is performing as expected?

This site allows you to enter more specific information about your location, and installation:

PVGIS

It's not as bad as it looks. You can play with the finer details all you like, but at first only really need to complete;

Installed peak power - e.g. 3 for a 3kWp system
Mounting position - free standing
Slope - e.g. 30deg
Azimuth (point of reference, the sun) - e.g. for South 0deg, for East -90deg, for West +90deg

Click on the map where you live
Click calculate.

You will then get a page of info, and a table giving an estimate of monthly and annual generation (column Em).

Remember this is only an estimate based on average solar levels of the last 30 years. Generation will vary and will be affected by shading.

There are many weather sites available on the internet, and these can be used to predict short term generation, or to help decide when you think it'll be best to set timers to run appliances etc. You may find it useful to find a site that you are comfortable with, however there does not (at this time) seem to be any one in particular that stands out for recommendation.

At the end of each month you may also want to compare sunshine levels for that month against a 30 year average in the UK. This can be done on this site, just choose the sunshine report map from the list of options.

http://www.metoffice.gov.uk/climate/uk/anomacts/

Some recent MSE threads:

How do your 12 month generation figures from PV compare to estimated?

Renewables: "talking 'bout my generation"

So now I have a solar PV system how do I make the most of it???


Sections 6 onwards are found here (click on the white chevron):
Martyn1981 wrote: »
Solar PV Q&A's Index PTII
Mart. Cardiff. 5.58 kWp PV systems (3.58 ESE & 2.0 WNW)

For general PV advice please see the PV FAQ thread on the Green & Ethical Board.
«13456711

Replies

  • Initial thoughts: Wow! Impressive start. Great basis to work from. :T
    Are you for real? - Glass Half Empty??
    :coffee:
  • albyotaalbyota Forumite
    1.1K posts
    Brilliant work Mart, some fairly up to date Q&A's concerning FIT's & EPC's here from DECC.

    http://www.decc.gov.uk/en/content/cms/meeting_energy/renewable_ener/feedin_tariff/fits_faqs/fits_faqs.aspx

    AL
    There are three types of people in this world...those that can count ...and those that can't! ;)

    * The Bitterness of Low Quality is Long Remembered after the Sweetness of Low Price is Forgotten!
  • jimjamesjimjames Forumite
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    Martyn1981 wrote: »

    Got to admit I was quite worried about putting much down about FITs, and finally chickened out of giving a financial example of an 'average' install. Too risky and potentially misleading, plus it might stifle debate..
    Thats a great post Martyn. In relation to the FITs and electricity the one thing I would say is to caution anyone who is getting quotes to be very careful when suppliers use high figures for electricity price RPI. We had some using 15% compounded over the 25 years when that is clearly an unknown and if actually true would mean electricity was 70% of an annual salary if RPI remained under 5% as they also suggested in their calculations. By giving such large numbers it helped make their case for the "financial investment" into solar.

    I guess what I'm saying is that for any payback calcs there are elements of estimation but it is better to use more cautious figures and always consider the effect of compounding which some unscrupulous suppliers are trying to use to their advantage.
    Remember the saying: if it looks too good to be true it almost certainly is.
  • Former_MSE_AndreaFormer_MSE_Andrea Forum Manager Former MSE
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    Thanks for the email Martyn, stickied :)
    Could you do with a Money Makeover?


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  • EricMearsEricMears Forumite
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    Martyn1981 wrote: »
    I'm sure bills will keep going up by more than inflation for a while, especially as we buy more and more imported gas, but there has to be a natural cap at some point.

    So I assume there has to be a price point where electricity 'only' goes up with normal inflation? Maybe today + 50%?

    Mart.

    I would suggest completely ignoring the effects of inflation.

    Nobody can tell you with any certainty what next year's inflation rate will be (HM Treasury & OBR are always happy to issue a forecast but their reliability isn't impressive !). Following year's is even vaguer and Y25 a complete mystery.

    If a deal is worth doing at this year's rates it will always be so if corrected in arrears for inflation; if it's not worth it this year then it's unlikely to get much better.
    NE Derbyshire.
    4kWp S Facing 17.5deg slope (dormer roof).
  • Martyn1981Martyn1981 Forumite
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    EricMears wrote: »
    I would suggest completely ignoring the effects of inflation.

    Nobody can tell you with any certainty what next year's inflation rate will be (HM Treasury & OBR are always happy to issue a forecast but their reliability isn't impressive !). Following year's is even vaguer and Y25 a complete mystery.

    If a deal is worth doing at this year's rates it will always be so if corrected in arrears for inflation; if it's not worth it this year then it's unlikely to get much better.

    Cheers to you and Jim. I've added a small bit about ignoring overly large estimates of future leccy savings.

    ***Breaking news***

    WE'VE GONE STICKY

    Thanks MSE, and thanks again to one and all for all the advice, ideas, contributions and support. Let's hope we've helped a little bit.

    From Chuffed in Cardiff

    Martyn.
    Mart. Cardiff. 5.58 kWp PV systems (3.58 ESE & 2.0 WNW)

    For general PV advice please see the PV FAQ thread on the Green & Ethical Board.
  • CardewCardew Forumite
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    Perhaps in Section 3 a warning (for those with Gas CH) that using an immersion heater, to 'use up' surplus generated electricity, can actually cost you money unless you can be sure that approx 2kW of PV generated electricity is available.

    If Gas costs approx 4p/kWh and 'imported' electricity approx 12p/kWh. So if immersion heater is using 1kW of imported electricity and 2kW of PV electricity, the cost is the same as using 3kW of gas.
  • CardewCardew Forumite
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    jimjames wrote: »
    In relation to the FITs and electricity the one thing I would say is to caution anyone who is getting quotes to be very careful when suppliers use high figures for electricity price RPI.

    The price of a unit(kWh)Electricity used in all these calculations is that approved by Ofgem and indeed the EST use that figure.

    That figure is very 'convenient' for the companies to use(it is around 14p/kWh) as they can state truthfully that it is the approved figure.

    However that figure is arrived at by including the standing charges for electricity(i.e. Tier 1 rates or Daily Standing Charge) and ignoring the discounts offered.

    The representative figure that should be used is only the Tier 2 rate, as any savings will be 'off the top' i.e. not including Tier1/DSC.
  • EricMearsEricMears Forumite
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    Martyn1981 wrote: »
    Thanks Cardew, I've enlarged the warning section on bill savings, to include tiered prices, and added a section on heating water in the 'getting the most out' section. Perhaps in a few years (well maybe 10?) when we all have smart meters, the small difference in price between gas and exported electricity will make redundant any efforts to use PV over gas.

    Mart.


    I see you're currently saying "Savings will vary from household to household, but could be approx. £100 (somewhere in the £50 to £150 range)."

    I don't disagre with it probably being around £100 but the maximum saving could be rather more than £150. I based things on an annual generation of 3000kw (1150 in the worst six months of my first year and over 400 in the month since then makes that eminently surpassable). If I could use all of those units on something I'd have done anyway they'd be worth 10p each to me (so £300). I'd probably be replacing night E7 units rather than full price ones so my maximum saving won't be that much but it remains do-able for some people albeit unlikely for most.

    To make that sort of maximum saving, you'd need to be a very heavy daytime user e.g. someone running an engineering works in their garage or a home ironing service with several operators. But I'm sure there will be someone out there who really could benefit that much.
    NE Derbyshire.
    4kWp S Facing 17.5deg slope (dormer roof).
  • EricMearsEricMears Forumite
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    Martyn1981 wrote: »
    It's a tricky one Eric,

    "larger savings are possible, but are rarer, and would require higher daytime consumption."


    Edit: is £50 min ok, or a little low, I'm thinking 500 units of baseload, on a smaller system 2kWp or so? Some sites suggest £70, but maybe better to underestimate.

    Mart.

    PS I think it's getting there slowly?

    It's not something I feel all that strongly about. The quote I've left intact looks fine.

    As to minimum - that's got to be zero surely ? A house left unoccupied for a month or so with fridges, freezers & CH system turned off would gain no benefit at all. Again, a rare set of circumstances but not impossible.
    NE Derbyshire.
    4kWp S Facing 17.5deg slope (dormer roof).
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