In July 2024 we had domestic solar installed at our house, as depicted above. I.e., 16 x 475W (7.6 kWp) AE panels on the roof of a slatted shed adjacent to the property, connecting through ducting laid under a lawn to a Solis S5-EH1P5K-L hybrid inverter. The Solis inverter works well, has good interoperability with most battery suppliers, and even has integration with Home Assistant for example. Installing the inverter in the garage is neat as there are no external blemishes on the buildings, and even though IP65 rated, internal installation should prolong the lifespan of the inverter. Also the garage had appropriate connections to the house already, simplifying the install. The most awkward bit was digging the trench for the AC and DC cable ducts between the shed and the garage, but I was able to do so myself with pick and shovel to the appropriate ducting standards, remembering to leave a draw rope in place for the installers to pull their cables through.

The total cost of the system was €7700, which after the €2100 SEAI grant, cost €5600 net. Our electricity cost went from about €2500 per year to €180 per year. Assuming an opportunity cost of earning 7%/year in the markets on that €5600, gives a payback period of about 3 years. Another way to look at it is, over the estimated 30 year lifespan of the system, you get ~8.5%/year compounding return on the cost. This beats the long term return of the S&P 500 for example, while also helping to reduce carbon emissions. Note electricity prices will probably rise in future too, which will further increase the returns. Given all the variables involved, I've created a solar vs equity calculator to help visualize the returns over time.

We did not install any batteries initially because FIT rates in Ireland are quite good at present (~€0.20/kWh), and also the installer was charging €2500 extra to add a 5kWh battery, which we felt wasn't good value. We did however install a hybrid inverter to give the flexibility of adding batteries in future, which cost about €900 extra over the price of a string inverter. Note the economics of batteries are trickier to compute, given the possibility of load shifting etc., but if we do install batteries, it will probably be 10kWh and we'll consider it when the cost for 10kWh is around €1500. You do pay VAT if installing batteries independently from panels, but that becomes less significant with lowering cost. [Update Jan 2026: Batteries have now hit this price point, as detailed in the battery section.]

It's very important one chooses the appropriate electricity supplier / plan to get the best value from your solar install. A great way to help choosing from the hundreds of plans available is to (assuming you have a smart meter), upload a HDF file obtained from esbnetworks.ie to energypal.ie. This site is useful even if you don't have solar, but is especially useful with solar as it incorporates your grid exports and FIT rates from each electricity supplier.

There are various factors affecting the operation of the panels, and I found the purevolt calculators good for comparing various angles and orientations. The main advice I'd give here is to not overthink orientation as it's not a very significant factor. My panels have an inclination of 9.4° (best for our latitude is 37°) and azimuth of 237° (best is 180°), but we only lose maybe 15% due to that non optimum orientation. Ground mount systems have more flexibility in orientation, and I've even seen systems that can adjust their inclination (shallower is better in summer, and vice versa).

One thing we would advise to triple check is shading, as this can be significant and is the main thing you have more info than the installer on. Looking at the roof or site at various times on a sunny day, preferably at different parts of the year, is a good way to determine this. Note even a shadow of a wire on a single panel is significant and it can increase the resistance of shaded cells, thus reducing the performance of the whole array. It can also decrease the lifespan of the panels due to the heating of shaded panels due to the increased resistance. Our panels are partially shaded for part of the year by an electricity pole, which we only realized after the install. If we had noticed before the install we probably would have installed optimizers on the impacted panels. I've calculated our losses due to shading at about 8% so luckily it's not too bad in our case. We also noticed (through temperature touch test) that the "built-in optimizers" in our AE panels work well, and bypass cells once enough cells in a group are shaded.

In retrospect we would have installed a changeover switch which is cheaper as part of the initial install, but more expensive if retrofitted. Especially since we were hit with storm Eowyn this year and were without power for 3 days, though we did have backup DC power for our phones and network at least. With a changeover switch one should be able to power the whole house to 5kW, which would suffice for lights, traditional central heating systems, and basically all non heating electrical equipment in the house. This would be most useful with a battery installed of course. Note one can and should configure things with a changeover switch so that the solar panels are left enabled with the battery power, so one can avail of solar power in the event of a grid failure. Note also that the Solis inverter has an AC backup port built in, which one could connect to a separate circuit (say central heating + lights). The AC Backup output blends power from all 3 sources; solar, battery, and grid. Another consideration when designing your backup power setup are the newer Electric Vehicle standards like V2L, V2H, and V2G, and how they might feed their significant power stores to your home.

Battery

We purchased a Fogstar 16.1kWh 48V, seplos BMS based battery, for €1900 in Jan 2026, as it's now economically beneficial to do so. Note it's an IP20 system, providing no water/moisture protection, and so must be placed inside (our garage).

The installation is relatively straightforward, being essentially, turn inverter off, plug battery in, turn inverter on. Note one caveat with the Solis inverter is that it requires DC input to turn on, so if installing at night (with no solar input), you'll need to ensure the battery is fully on before the inverter will turn on.

Some of the inverter battery settings can be configured in the (App), and some only on the front panel (FP); in summary:

The cable gauge/length is an important consideration when connecting batteries together, and to the inverter. The Solis inverter can do 100A (5kW), while the battery can do 100A charge, 200A discharge. Consequently the inverter came with 4 AWG 21.2mm² cable, while the battery (51V) came with 1/0 AWG 50mm² cable. Given the inverter supplied cable is about 7ft round trip, according to this battery cable sizing guide it should (just) suffice for the up to 100A loads. Though I set the charge and discharge rates to 50A and 90A respectively, to both minimize wear on the battery and loss in the cables. Note the power loss due to resistance in this length of 4 AWG cable would be about 4W, 14W, 20W for 50A, 90A, 100A respectively.

Another current consideration is to ensure one doesn't overload the main premises input when charging from the grid. That's another reason I set the charge limit to 50A, as only an extra 2.5kW in combination with a 10kWh shower should be fine for our 12kVA setup. Note we also have a 7.2kW car charger, but I've configured import limit protection on that Zappi charger which will throttle back if the combination of house + inverter charging is too high. Therefore we only need to worry about the combination with house loads, so 2.5kW should be fine. I would have expected the Solis to support import limit protection, but I can't find an explicit setting for that.

Other safety considerations are isolation and grounding. I didn't install a separate isolator switch for the batteries, as the battery itself has a switch on the side, and also the Solis inverter has a DC isolator switch built in at the bottom. As for grounding, the battery has an earth connection point on the back, while the Solis has one on the bottom right side, so I connected these together to ensure the battery is grounded appropriately.

Picking which storage strategy to use to maximize the economic return is complicated and varied. It depends on varying electricity costs, time windows, solar production (tomorrow's weather), ... Therefore there may be use for auto adjusting all the various parameters, like charging slots and charging rates etc. using a dynamic system external to the inverter, though the integrated Solis configuration does provide some flexibility. The main thing to consider with a battery, especially a larger battery like this, is to maximize the use of load shifting. I.e. to minimize the cheapest rate available, which then can be distributed to the house during more expensive times, or even dumped to the grid if the spread between the export rate and cheapest rate is big enough. Our export rate is 33% higher than our cheapest rate, and daily rate is 100% higher, so we both power the house from the battery during the day, and then dump any excess to the grid late at night. If the FIT ever reduces towards the cheapest rate, then the strategy would change, to ensuring more solar is stored, and not dumping at night. A top tip for evaluating all these options is to use the excellent killowatt.ie calculator.

The Solis charge and discharge time slot configuration can be a bit confusing. The main thing to note is that battery is not used for house loads during any configured time slots. Well house loads will implicitly use the battery energy first during actual discharge, but once the target battery percentage is reached the battery will not be used for house loads until the end of the discharge slot. Also there is no way to reserve a battery % until peak time, but this is less of a consideration anyway for a larger battery like this. Though again lots of potential for a more sophisticated external system to dynamically adjust the storage strategy.

Adjustments

The system now runs issue free, but there were a few teething troubles...

We needed to switch the installed 30mA RCBO to 100mA. The system tripped out a couple of times with the lower rated component, requiring manual intervention to reset. Thankfully my installers did replace the RCBO for free. Note the Solis inverter has built-in 30mA protection, so the external 30mA breaker was overkill, and anyway the standards changed (after my install) allowing a 100mA RCBO in Sept 2024.

We needed to switch grid CT direction after an auto firmware upgrade on the Solis inverter reset the setting to the incorrect orientation. The symptoms here were that generated power was depicted as being consumed, and vice versa. The independent smart meter wasn't affected of course, just the monitoring in the Solis app, though there could have been knock on impact with more complicated setups with batteries etc. I contacted Solis support, who were able to promptly fix the issue remotely.

As part of the above support fix they also enabled 24 hour monitoring mode which we didn't want. With this setting disabled, the inverter will automatically turn off when there is no solar production. I estimate that auto turning off at night saves about €50/year, so it's worth adjusting that which again Solis did remotely. We would run the inverter all the time if ever installing batteries though, to avail of load shifting and cheaper night rates. Note this and the previous CT setting do not seem to be settable in the Solis app or on the inverter screen menus, and must be done remotely by Solis which isn't ideal. Note to change settings on the Solis, you can use the "control inverter" menu on the app, or use code "0010" to get access directly on the inverter display.

We needed to change the "grid standard" setting on the inverter from "EN50549IE" to "ESB Micro". This avoids occasional disabling of the solar panels, where the output was seen to go to 0kW for a few minutes on sunny days. I plotted grid voltage in the Solis app, and it creeps up to 250V when this happens. I.e. my Solis inverter throwing OV-G-V01, and disabling generation for a short while. I saw that the grid standard was set to EN50549IE, as displayed on the inverter screen, showing a limit of 253V (for 0.5s). Displaying the "ESB Micro" option shows it has an overvoltage limit of 269V (for 70s), and since setting to ESB Micro production has never dropped. Note this more relaxed setting is as specified on the NC6 form, and corresponds to the 2022 update to EN50549.

We also got a Zappi car charger when installing the solar system, and in the same theme of settings not being adjusted appropriately, I needed to set the "grid limit"/"import limit" on the Zappi, as it was potentially unsafe. If for example the house was drawing 63A and the Zappi 32A, it would blow ESBN fuse at best, or start burning something at worst. Given we're 12kVA (as shown on esbnetworks.ie), I set the grid import limit in the Zappi to 52A, which usually doesn't impact the Zappi, but is significant when a 10kW shower is also on. I can see the zappi throttling down from 7.4kW to 3.5kW when this occurs.

I noticed a bump on one of the panels from afar, and when I inspected it I saw that it was a loose panel clamp for attaching the panels to the roof which had not been screwed down fully. Luckily there had been no significant wind before I noticed. It was easy to fasten down with a torx bit, but I'm sure we would have had issues during storm Eowyn at least. Definitely a case of a stitch in time...

The bottom 2cm of our solar panels accreted a lot of dust and debris, caused by water collecting there due to the shallow 10° mounting angle and raised lip around the edge of each panel. This debris has the same issues as discussed in the "shading" section above. Panels generally are generally auto-cleaning if mounted at 15° or more, and our panels are fine actually in this regard, apart from this 2cm at the bottom. I was able to address this issue by installing (plastic) "solar panel water drain clips" which I got on amazon for around €0.30 each (there were Irish suppliers charging 10 times that). My panels are 30mm, so check your panel specs for the appropriate depth.

© Jun 14 2025