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Interested in Solar PV? Read this FAQ first.

  • 24-02-2022 11:17pm
    Moderators, Education Moderators, Home & Garden Moderators Posts: 7,829 Mod ✭✭✭✭

    This post aims to be basically an introduction to the route that most people will take when onboarding onto the “Solar bandwagon”. It doesn’t answer every single question, and that’s where the forums will help, but reading this first will arm you with a lot of the knowledge to successfully get solar installed in your house, hopefully without costing an arm or a leg. In addition to this post, you should also read the helpful SEAI FAQs available here:

    Thanks in particular to @bullit_dodger and @yankinlk for their work in putting this FAQ together. To add/amend any FAQs below, PM @Jonathan or @graememk

    Step #1 - Do not install Solar PV before FIRST trying to reduce your Electricity Bills.

    • Can you reduce consumption by turning off lights or devices?
    • What is your electricity Plan - have you tried switching? is a good place to start. Shopping around can save a LOT of money and is free!
    • Install A-Rated appliances and use LED bulbs etc to help reduce your base load. Lights are a particularly easy and quick way to reduce your bills. Those old halogen spot lights at 50 watts each can be replaced by 6 watt LED versions, saving you 85%+ of your lighting costs. While 50 Watts may not seem like a lot, when you have 4 or 6 of them and they are on for hours every day, it adds up to a tidy sum. 

    Step #2 - Done that.  Now should I install Solar PV?

    • In order to accurately size the system that you should install, you first need to understand what you need and this involves understanding what is your annual consumption of electricity? Are you above or below the national average? (Irish average = 4,200 kWh) 
    • Then once you have the amount, you need to understand HOW you use it. Can you make hay when the sun shines? I.e. Can you consume the electricity you create during the daytime? Or do you leave home early and arrive back in the evening? The priority of any system should be for self-consumption - using it during daytime especially during the brighter months (April - September) Understanding these things will help in your decision making, For example if you’re not there during the day when it’s sunny you might consider getting a battery to store that energy
    • Are you using electricity for cooking? Lawn mowing? Electric Shower? Heating systems? The more you are using should be reflected in your annual consumption, and it’s important to know what you're using so you can buy the right equipment. 

    Step #3 - But how much will it cost?

    • Really - it depends. There are many factors - but you can start by asking for a quote from a supplier.  They should ask you for your address and your annual consumption - and ideally design a suitable system based on your roof size and orientation. The “orientation” is where does the roof face. Is it South facing, (and the other side of the house) to the North, or is it SE/NW, etc. 
    • Once you have a quote - you can post it here to have it evaluated.
    • What have others built and how is it working out? Look at this Spreadsheet from boardsies. There are tabs for install details and monthly performance.
    • There is a very rough formula that people use.

    €1.2k per 1kWp in panels + €1K per 2kWh in battery + €550 (diverter/Eddi) = Rough price to pay. 

    We should note that the formula isn’t a “golden rule” where if you are paying more then you are overpaying, but rather it’s a general “target” to try and achieve. If you are getting within 5-10% of the figure then you are probably doing ok. 

    Additionally for smaller systems, it’s harder to match the quote to the estimation. This is normal. 

    If you are still in doubt, plug your figures into this calculator:

    Should I Build or Buy a PV system and what about SaaS? 

    • Are you great at DIY?  Can you access your roof safely?  Would you project manage this yourself and source all the parts?  DIY is a very viable option - a lot of advice available here.
    • Do you prefer to pay for a qualified SEAI installer to handle everything? GO back to step 2 - gather all your requirements and look for (at least) 3 quotes. 
    • What is Solar as a Service? For a smaller system, Solar as a Service option can be very hard to beat. This a system whereby you pay no upfront costs, but rather pay a monthly fee for a fixed period - think Hire Purchase.


    Should I get an EDDI?

    So first off an EDDI is a device which takes the “excess energy” that you are exporting to the grid (usually for free until the feed-in-tariff comes in) and uses that to heat the water in your immersion tank. 

    The general thinking is that EDDI’s while they are a useful and convenient device, for €500 or so, it’s unlikely that you will get that money back in the lifetime of the device. If you think about it, €500 will probably pay to heat your immersion tank once a day everyday for 3 years. 

    That said, while the return on investment may be questionable, many people do get in the EDDI’s as from April-October, it’s nice to have the convenience of hot water available for this “once off” fee. As many people have oil/gas boiler that they need to fire up to heat water in the summer months then the convenience of the Eddi is also worth considering.

    Should I install Optimisers? 

    Essentially these are used to optimize the performance of each of your panels. They can help if there is partial shading or if one panel is performing poorly compared to the others. Without them if there is shading on one panel - all panels may be affected and output reduced. Normally your solar provider will give you their advice during the survey phase for your unique roof and panel design. You will require optimisers for any panels which will become shaded at any time of the day. If your panel “string” faces more than one aspect, you will need optimizers on all panels.

    Should I buy a battery with my Solar Panels? Look at this thread for info on buying a Battery AND building a DIY battery.

    The main advantages of having a battery is being able to charge when there is excess during the day and then using that free energy to power the house in the evening.

    Another advantage, if house has a day/night meter, is being able to charge that battery on the cheaper night rate and then using this power when on day rate helping to offset the cost. If you work during the day and return to a house with a fully charged 5kWh battery then this may be sufficient to power the house until the night rate kicks in again.

    What size Battery should I add to my system?

    Start with "how many KWh do i use per day?" and work back from there. A good rule of thumb - 1/4 the amount you consume per day is a good starting point for a battery size. ie if you use 20Kwh per day then 5Kw battery probably makes sense. A larger battery may be usefull but also take longer to pay back.

    The key is to USE the battery everyday. You have to be able to fill it and drain it in every 24 hour period - for 10 years. This also means you need to be able to generate enough electricy from your panels to fill that battery every day... a bit like building a Computer... CPU, memory and GPU all work together - undersize any one and the whole thing runs slow.

    If I get a battery, can I run my house in the event of a power outage?

    There are various options for allowing for backup power.

    1. inverter powers 1 or 2 sockets via a backup connection using battery alone.
    2. backup option similar to above but is instead connected to a sub board, powering say 3-4 essential circuits.
    3. full consumer unit (but owner must ensure not to use more than panels+battery can supply) in this setup a manual changeover switch disconnects consumer unit from grid thus inverter backup supplying power to all house citcuits. This will typically also open the fireman switches to the panels thus allowing PV charge battery and supply house.

    I have an EV, will this make a difference?

    If an EV is going to be parked at home for considerable time during daylight hours then any excess solar, with a suitable charger, can be diverted to charge the EV effectively giving free fuel.

    An EV may make a difference in the decision to install a battery where the excess solar will be diverted to the EV and the need for a battery will need a bit of careful consideration.

    What is the difference between Solar PV and Solar Thermal and Solar Thermodynamic panels?

    Solar PV panels generate electricity from the sun. Solar Thermal panels (tubes) collect the heat from the sun and transfer it to your hot water tank via circulating glycol. Solar Thermodynamic panels are essentially specialised heat pumps which use compressors to collect the heat from the sun and transfer it to your hot water tank.

    Does my Site Location make a difference?

    Can I get paid for the electricity I generate and sell it back to the grid?

    The short answer is No - for Domestic customers - there is nothing in place yet to pay people for their excess solar that goes back to the grid. For now, the goal is only to build a system that can generate enough energy for you to self-consume on site that energy. In future it remains to be seen if there will be a fair rate to consumers - so don't oversize that system hoping you will make a fortune! Keep an eye out in the forums for any mention of FIT, CEG, CEP or MSS - when it finally gets announced and goes LIVE you will definitely hear about it in these forums! 

    UPDATE Sept 2022:

    Clean Export Guarantee has been announced and the rates are available here. The rates announced are considerably more generous than any of us here have expected, to the point that the economics of a battery are now questionable.

    CRU documents relating to CEG are available here.

    A discussion thread on CEG/FIT is available here.

    • What is the FIT? Feed In Tariff
    • What is the CEG? Clean Export Guarantee
    • What is the CEP? Clean Export Premium
    • What is the MSS?  Micro Generation Support Scheme
    • What is a Smart Meter?
    • Smart Meters are the newest digital meters that allow providers to be very granular with measuring energy used (and given back to the grid) by customers. They are being rolled out slowly across all of Ireland.
    • Here is a thread discussing Smart Meters and Tariffs - beware these meters are not YET any cheaper for the consumer - at some point they may be required to receive a FIT payment for excess solar - but most people are avoiding them where possible until Smart Tariffs improve.
    • What is a Day/Night (DN) meter?
    • Day/Night meters are digital and newer than 24H meters and allow energy providers to offer a Day and Night Rate. A valid strategy to reduce your energy bills is to shift as much usage to Night Rate Tariffs as possible.  Night rate kicks in after 11PM and ends at 8AM. It can be up to 4 times cheaper. Many of the solar PV users claim to be benefiting from Day/Night meters.
    • What is a 24 Hour Meter (24H)? 
    • Many older house still have an old analog style meter that “spins” a dial and only measures total KW units per day.  These are target to be replaced by newer Smart Meters.

    What do I need to do to get paid for selling my electricity back to the grid?

    Once your system has been installed, make sure that your installer has submitted an NC6 form on your behalf to ESB Networks. You cannot get paid for any exported electricity without an NC6!

    Confirm that your NC6 form has been submitted by emailing ESB Networks ([email protected] or esbne[email protected], both work) with your name, address and MPRN. See this post by @Granolite for more information.

    You may also need a smart meter to be installed, depending on your meter type (See next question).

    What meters that are eligible for FIT (as at April 2023)?

    Excerpt from Commission for Regulation of Utilities (CRU) email to a Boardsie:

    Regarding 24-hour meters - as they are MCC01 meters, it’s always been the case throughout the microgen scheme so far that those customers would only qualify for the export payment when they have a smart meter installed.

    This is because MCC01 customers are/have been eligible for a smart meter for some time now.

    Please Note: The deemed quantity is applied to customer waiting on a smart meter installation to replace a Day /Night Meter. As such, the deemed quantity is not applicable to you as you had a 24 hr meter.

    MCC01 (24 hour meter) – eligible for a smart meter

    MCC02 (day/night) – not yet eligible for a smart meter

    Customers who have day/night or other meter types qualify for the deemed payment, as their meter type is not yet eligible for a smart meter exchange.

    Commission for Regulation of Utilities (CRU), April 2023

    My house has Solar PV but no NC6 was ever filed. I cannot contact the installer. How can I rectify this and get paid for my exported electricity?

    See ESBN's Retrospective Micro-Generation Registration Process for details.

    Do I have to pay tax on my earnings from FIT?

    Yes, but each billpayer is entitled to a €200 tax exemption. More info here.


    What are solar panels?

    Simply put Photovoltaic (PV) panels are used to produce electricity directly from sunlight. Photovoltaic panels are inherently DC (direct Current)  devices and are rated as to the output in watts in what they produce. To produce AC (Alternating Current) which the electricity grid uses, they must be used together with an inverter.

    What is an Inverter?

    An inverter is a piece of equipment that converts the DC current produced by the solar PV panels to AC current which is fed back into the consumer unit to be used by the household or fed back into the national grid.

    Inverters will come in a few different types.

    String Inverter

    A string inverter is probably the most common type with a row/string of solar panels connected together and that string is then fed into the inverter. Inverters can handle one or more strings with the general domestic type taking two strings. This then converter the DC to AC and feeds back to the consumer unit,

    Hybrid Inverter

    A string Hybrid inverter is similar to the first but has the added capability of sending the solar generated to a storage battery.

    Micro Inverters

    These inverters are fitted to each individual solar panel and convert the DC to AC at the panels and remove the need for an individual string inverter. Because they are fitted to each panel if one or more are affected by shading then this will not affect the rest of the panels and each panel can be monitored individually. These can work out more expensive than a string or hybrid inverter.

    Storage Inverters

    A storage inverter is one that is not connected to any solar panels. A storage inverter is used to store and extract DC energy from a storage battery, converting this to AC which can be used within the house. An example of a popular storage inverter is the Sofar ME3000SP.


    As solar panels are generally connected in series to one another to form strings. If shading affects any of the panels on a string then the lowest-performing panel will impact the performance of the entire array unless each individual panel can be optimized.

    Optimisers enable each panel to work independently of other panels in the string. Unlike Micro Inverters Optimisers do not convert DC to AC and therefore a string or hybrid inverter is also required.

    Storage battery

    A battery simply takes the energy produced by the panels and stores it for use when required. As most households are empty during the day when solar is produced then rather than sending this back to the grid it can be stored and used when little or no solar is being generated.

    If a household is on a day/night tariff when prices are cheaper at night then the battery can also be charged at this time and then discharged during the day helping to lower the overall electricity bill.


    What space do I need, what does all this look like when done?

    Consideration will need to be made as to where the equipment is going to be located. This can be in an attic, garage or utility room for example. Ideally easy access to the consumer unit is helpful as a cable will need to be run from the inverter to this. So if in a garage or shed can a cable be brought from here to the consumer unit?

    How long does it take?

    This will vary depending on the complexity of the installation. Is it going in a two storey house or bungalow, are more than one aspect having panels fitted, is specialist equipment needed to access the roof? The installer will be able to advise but 2-3 days would be common.

    The photo below shows a typical installation with battery in an attic space. The inverter is on top with a 5kWh battery below. Then there is ducting, meter and isolator switch.

    The FAQ is too long. Is there an overview video I can watch instead?

    Yes! See below:

    2023 updated video:

    Post edited by Jonathan on


  • Registered Users Posts: 44,612 ✭✭✭✭Bobeagleburger

  • Registered Users Posts: 2,682 ✭✭✭yankinlk

    @Jonathan Can you add this to the FAQ if you think its a good enough answer:

    What size Battery should I add to my system?

    Start with "how many KWh do i use per day?" and work back from there. A good rule of thumb - 1/4 the amount you consume per day is a good starting point for a battery size. ie if you use 20Kwh per day then 5Kw battery probably makes sense. A larger battery may be usefull but also take longer to pay back.

    The key is to USE the battery everyday. You have to be able to fill it and drain it in every 24 hour period - for 10 years. This also means you need to be able to generate enough electricy from your panels to fill that battery every day... a bit like building a Computer... CPU, memory and GPU all work together - undersize any one and the whole thing runs slow.

    Post edited by yankinlk on

  • Registered Users Posts: 9,994 ✭✭✭the_amazing_raisin

    Thanks for the great guide folks, lots of good advice here

  • Moderators, Education Moderators, Home & Garden Moderators Posts: 7,829 Mod ✭✭✭✭Jonathan

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  • Registered Users Posts: 216 ✭✭sligopaul

    great stuff here for the first time browser


  • Registered Users Posts: 41 wayguk

    I'm reading about the planning requirements, they seem mental! only 50% of roof can be used? does that imply all my south facing can be used, but not my north facing (that works for me), but the 12m2 limitation which implies a very small deployment.

    does anyone know if/when this planning law is likely to change?

  • Registered Users Posts: 2,226 ✭✭✭bullit_dodger

    Ignore that 12m^2 limitation. It's a throw back to another time in Ireland. Everyone (and i mean EVERYONE) ignores it. I've 24m^2 on my own roof for example. Am I worried? No. Just had the SEAI guy out and verified everything ok. The only thing to watch out with installation is that the installer adheres to the minimum distances of the panels from the edge of the roof. Otherwise you can run into trouble with getting the grant from SEAI. If your not getting a grant, then of course "have at it"

    Note: Not sure, but it might make some sense to lock this thread? Dunno - I see two sides of keeping this open/locking it.

  • Registered Users Posts: 20 stiophan

    The roof panel law is either gone or no council is going to enforce it. I recall a solar user taking the council to court as there was no reason for the limit. No Irish government (especially now with high fuel prices) is going to enforce the rule. There will be limits to listed buildings (or at least the ones that face the public). I've seen a lot more rooftop solar (and solar thermal) owners expanding their panels over time. Many new homes had ONE panel on the roof which seems useless unless the rood is south facing without any shade at all. I don't recall the outcome of the court case but only a crazy council would take you to court on this law now (if its not already about to be removed). This limitation was not from the SEAI. However the SEAI does have a grant limit vs the amount of power you expect to generate. If Elon Must is going to offer solar roof tiles then this law would be meaningless (just leave the rest of the roof open to the weather???). There are some very innovative alternatives to PV panels at present but I doubt many Irish PV installers would be able to install them.

  • Moderators, Sports Moderators Posts: 17,888 Mod ✭✭✭✭slave1

    The more flexibe laws are not yet here, they are in the Seanad so still have to go through the Dail. The only obstacle is a Karen neighbour who objects and then the local Council will have to act upon...

    Planning and Development (Solar Panels for Public Buildings, Schools, Homes and Other Premises) (Amendment) Bill 2021 – No. 88 of 2021 – Houses of the Oireachtas

    The main update for the likes of us is removal of the 50% of roofspace but more interestingly Ground Mounts up to 4m high without Planning

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  • Registered Users Posts: 107 ✭✭private

    Hi, I'm definitely solar curious. Currently have solar thermal water panels that do a good job. They came with the house which is a new build A3 rated 3 story south facing built 2018. A smart metre was just installed. I have a flat roof for the most part. (3 story). The water panels are on a part of pitched part of the roof that is south facing so only the flat roof is available. I'm at home during the day so can use electricity for dishwasher/dryer etc then. Our electricity usage for the past 2 years averages 5000kwh. I'll make enquiries with some companies and see what they quote.

  • Registered Users Posts: 77 ✭✭abyss

    Does the off-grid system (electrically separated from ESB network!) also have to be reported to the SEAI or other authority? I don't want to sell electreicity, I dont want grants.

    (free standing solar panels, DIY maintenance - I have skills with DC systems and currents as high as hundreds Amp range, fuses 400A was thicker than my fingers :) )

  • Registered Users Posts: 489 ✭✭bakerbhoy

    looking at pv panels and battery.

    Annual consumption circa 7800 kw. Already have solar thermal from original build.

    Quoted 19k for 7.6kWp system including batterys

    Opinions welcome

  • Registered Users Posts: 1,133 ✭✭✭DC999


    Pop it in the quotes thread instead and you'll likely get some feedback. This one is more a sticky, so won't get seen.


  • Registered Users Posts: 489 ✭✭bakerbhoy

    Yes spotted that after I posted.Done.

  • Registered Users Posts: 4,136 ✭✭✭con747

    @Jonathan Maybe lock this sticky?

    Don't expect anything from life, just be grateful to be alive.

  • Moderators, Education Moderators, Home & Garden Moderators Posts: 7,829 Mod ✭✭✭✭Jonathan

    Done. PM me if you want any updates made to FAQ.

This discussion has been closed.