If you have a new account but are having problems posting or verifying your account, please email us on [email protected] for help. Thanks :)
Hello all! Please ensure that you are posting a new thread or question in the appropriate forum. The Feedback forum is overwhelmed with questions that are having to be moved elsewhere. If you need help to verify your account contact [email protected]

Guide to electrical solar panel self-install

  • 17-08-2022 10:11am
    Registered Users Posts: 705 ✭✭✭

    Ive mostly lurked on this forum for information on PV solar panels installations. There is some fantastic information here, so I wanted to try and do my bit giving back some information by outlining how we did our own solar PV install. We were building a new block garden shed, and decided to look into installing solar panels on the roof. We had a family friend who was a RECI electrician and could help where needed.

    Specification has an online designer, where you can specify the number of panels that you need, and it will output a Bill Of Materials (BOM) for you to purchase. You can then purchase the materials from them, and they will deliver it all on a pallet within a day or two. For our installation, we wanted 6 panels as it was the most that could be installed on the south facing side of the roof of the new shed that was being built. Some highlights of the final BOM was:

    • 6 x 360w panels (2160w in total)
    • Solis Mini 2Kw 4G inverter
    • “K2” mounting system for slated roof
    • Overall cost of kit: 2247e

    All parts were included, bar the following: 

    • 50m 3 core 4mm2 armored AC cable 
    • This ran from the consumer unit in the house to the inverter in the shed. 
    • Cost: 170e
    • 4” conduit to bury the armoured cable in the garden
    • Trunking and clips for cables, for running the AC cable up the shed and house wall. 
    • Aluminum paneling to place the trunking/cables behind on the shed wall.

    Approx overall cost of materials: ~2500e

    Return on investment

    I used the Irish Government's SEAI online calculator to find out how much money we would save.

    So it looks like we would break even after roughly 7 years, and save 341e every year after that. Note that this was calculated before Putin decided to invade Europe, so the savings are better now due to the increased cost of energy. 

    To be honest, doing a self-install does not save as much as you would expect compared to getting a professional to do the install due to the very generous grants available. These grants are only available if the installer is a SEAI registered installer, not just a RECI electrician. However, there is still a saving to be made, and I was looking for a project to do, so this looked like an interesting one to learn from.

    Installation of the panels

    The roof was to be done using bangor clay tiles, as shown below: There was an error displaying this embed.

    These are pretty thick in size, so solartricity were emailed who recommended their flashing kit for cable entry and “K2 Roof Fastner for flat tile, 15cm”. 

    The overall kit with these fasteners was ordered. The roofer finished installing the roof tiles. We left the scaffold up for easy access to the roof. Solartricity provided an installation PDF guide for the overall system. 

    This was used to mount the brackets for the mounting rails. Each mount point was marked on a tile and the tile removed using a long flat head screwdriver. The roofer was asked to order a few spare tiles for breakages. Thankfully it was possible to remove all the tiles needed without breaking any. 

    The guide specifies that the hook is screwed into the timber plant, which is in turn screwed into the rafter. I asked our roofer about this. He said that he could see no need why this was suggested, as it should be better to screw the hook directly into the rafter. As the shed was not in a high-wind load area, we went with this approach. 

    Shims were cut to ensure that the hooks cleared the tiles correctly, as shown from the instruction manual below: 

    The panels were mounted to the rails using their clamping system, shown below: 

    The installed panels are shown below. 

    Each panel has a female and a male “MC4” connector on a tail. This allows for them to be easily connected in series. 

    Female connector

    Male connector

    A long tail was added to the first and last panel with enough DC cable to bring it through the attic for connecting to the inverter. These two connectors were carefully crimped with a proper crimping tool. I bought a couple of spare MC4 connectors off amazon. 

    An earth had to be run from each panel. This was trickier to install, as there was no obvious connector on the panels, nor was the method described in the manual. As a result, outdoor earthing clamps were purchased from Screwfix and mounted to the aluminum frame of each panel.

    A loop was made to each panel in series. 

    For entry of the cables into the roof, a notch had to be cut in one tile with a junior angle grinder with a diamond blade. This allowed the flashing to be installed. 

    Flashing for cable entry through the roof

    Notch cut in tile for the flashing

    The installed cut tile, flashing, and the entry of the three cables is shown below: 

    A small hole had to be made in the breathable moisture membrane below the cable entry flashing. All cables were secured with cable ties below the panels to keep them away from the elements as much as possible.

    Next, onto the installation of the inverter.

    Post edited by SchrodingersCat on


  • Registered Users Posts: 220 ✭✭ColemanY2K

    very impressive and thanks for the guide.

    one thing i noticed was the day time unit rate for electricity you used with the SEAI online calculator was 0.195 cents. Surely its much higher than that? and if so it would bring down the pay back period.

    i'm trying to convince the folks to install something similar. this is what i'm getting when i plug in their details.

  • Registered Users Posts: 705 ✭✭✭SchrodingersCat

    Yep, the unit costs are much higher now.

    The 0.195 cents was accurate at the time that I did out the calculations.

    The 3kW figure in your image is nice size for a solar array. One of my regrets was not being able to fit more than 6 panels on the roof. I also probably would have oversized the inverter to future proof it, in case I wanted to mount additional panels off to the side of the shed.

    if your folks do decide to go down the same route, make sure you have a RECI electrician lined up to help, you will need it to get the NC6 form signed for the ESB and probably for the final certification.

    Beat of luck with it!

  • Registered Users Posts: 4,370 ✭✭✭Gerry

    Great thread, fair play to you for putting up such a detailed writeup.

  • Advertisement
  • Registered Users Posts: 1,582 ✭✭✭andy125

    I wonder is it economical to saas for the basic package with an upgraded 6kw inverter and then install more panels and a second string on the other side of the house diy, so a 2.7kwh install saas with grant and then upgrade to say 8kwh diy?

  • Moderators, Education Moderators, Home & Garden Moderators Posts: 7,823 Mod ✭✭✭✭Jonathan

    I've added this to the Key Threads sticky.

  • Registered Users Posts: 705 ✭✭✭SchrodingersCat

    Probably, but it would depend on how much they are quoting you for the 2.7kWh install (with 6kW inverter). You could work it out after that:

    If you have that quote, add on the cost of 8kW - 2.7kW = 5.3kW of panel, which is ~12 panels. Solartricity sell them at around 160e a panel so about 2000e worth of panels. Add on the cost of the mounting system (check solartricity and the type of roof that you have), and the length of DC cable that you need (this is normally cheap) to give you a final cost for your SaaS & DIY install.

    Then get a quote off the SaaS for a 8kW install and compare both figures against each other.

    Just to note: I know that they recommend that you undersize your inverter compared to the solar array for efficency, but running a 6kW inverter off a 8kW solar array sounds like a bit too much.

  • Registered Users Posts: 3,054 ✭✭✭irishchris

    Excellent guide and well put together. one quick query on the earthing of the panels as was something not certain of when doing my own self install. Should the panels be earthed to the ac earth connection. as would imagine the idea of earthing panels would be to protect from dc voltage error or lightening. I am not sure running the rare risk of dc power escape being earthed to ac systems earth is good idea but maybe I am wrong? I earthed my panels to a separate ground earth rod and will be adding a dc spd and breaker for each array in between at a later date

  • Registered Users Posts: 2,213 ✭✭✭bullit_dodger

    Funny, I had the same conversation with a spark I know if you should have a separate earth for the DC side of the house over the existing AC side. His take on it was that "earth is earth" and that while it's true that you might have something checking earth leakage etc, it shouldn't ultimately matter.

    The panels could in theory get energized and with it being a ground mount in my case (true for you too Irishchris?) in theory someone could touch it and get a zap, so I just earthed it to the AC. Less likely on the roof, but I guess someone could touch one of those via a velux window. In my case it was also complicated as I've got micro-inverters centimeters from the panels, and of course the micro-inverters have 230 AC running in/out of them. But yeah, I used the AC earth and didn't run a separate DC earth.

  • Advertisement
  • Registered Users Posts: 1,582 ✭✭✭andy125

    My worry would be that as you don't own the install there could be some bother with adding panels to the system yourself.

    Regarding the 8kwh panels into the 6kw inverter, it would be 4kwh NE and 4Kwh SW so I would imagine it would be ok as chances of both strings hitting 4kwh for a prolonged time if at all seems unlikely but open to correction.

  • Registered Users Posts: 2,213 ✭✭✭bullit_dodger

    Could do in the middle of summer when the sun is sort of more "overhead" than aligned with any particular roof direction at noon. Even if you didn't get 100% output, and got say 80%, that would be (4kw x 80%) + (4Kwp x 80%) = 6.4Kw so you could easily exceed the inverter rating.

    Fret not though, inverters will only suck down what they need and they will "clip" the rest of the generation as something surplus. So if you had 8Kwp in panels (and you could get 8Kwp from the sunshine that day), the inverter will only draw down 6Kw. it's not like a wind turbine where it will destroy itself if you don't use what you generate.

    Best bet though is to look up the inverter specs where they will tell you the max wattage to hook up to. Generally it's good practice to oversize the panels by 30-50%, but again best confirm that the inverter can handle it from the datasheet.

  • Moderators, Home & Garden Moderators Posts: 4,426 Mod ✭✭✭✭graememk

    Yep mines all installed to the house earth.. but not to each panel, On the slate roof it was to the rail (rail touches all panels) and on the steel roof Its to one of the mounts.

  • Registered Users Posts: 705 ✭✭✭SchrodingersCat

    My view is what bullit_dodger said: "earth is earth". So there should be no need for a separate earth for the panels. I guess if there is a worry about lightening, what you could do is drive an additional earthing rod into the ground and run the earth cable from the panels, to the earthing rod, and back to the AC circuit. Hopefully that would give the lightening the shortest, and safest, path to ground. I'm no expert on this though.

    I would imagine that any modifications that you make to the SaaS install will void your warranty with them. It would be up to yourself if you were happy with that risk. By rights, the ESB should be notified of the increased capacity, but I doubt that they would be too interested. Yea, thats a good point by yourself and bullit_dodger, worst case scenario you will just lose out on potential solar generation by under speccing the inverter. As the peak generation typically only lasts a couple of hours in the day, I would imagine that you wouldn't lose out on that much power anyway.

    Post edited by SchrodingersCat on

  • Registered Users Posts: 1,460 ✭✭✭poker--addict

    I am not sure SAAS will even entertain a quote for larger system? Or will provide one massively inflated.

    This used to be a referral link 😎

  • Registered Users Posts: 576 ✭✭✭Whatwicklow

    Excellent write up, well done and congratulations on the installation.

  • Registered Users Posts: 1,323 ✭✭✭Nelbert

    Fantastic write up.... To the point I'm a lot more comfortable with the idea of a self install myself.

  • Registered Users Posts: 4,370 ✭✭✭Gerry

    I don't have a problem with the DIY but getting on the roof is a bit off putting. will figure it out.

  • Registered Users Posts: 5 hwshaw

    Does the meter not need to be connected with the current clamp. The wired with RS485 back to the Inverter. Not just a nice to have?

  • Registered Users Posts: 705 ✭✭✭SchrodingersCat

    No, not unless you need to know how much energy you are sending back to the grid. For example, for a hot water diverter or battery charger, for example.

  • Advertisement
  • Registered Users Posts: 89 ✭✭daesal

    Thanks. Great write up. Appreciate the extra time it took during install to photo everything for us. :)

  • Registered Users Posts: 6 Seventy Plus

    Thank you for going to the trouble of putting all of it up.