Solar for Beginners [ask your questions here]

Have a read of the FAQ.

Interested in Solar PV? Read this FAQ first. — boards.ie - Now Ye're Talkin'

it's got a lot of good information in there, including a general "rule of thumb" formula that people use.

€1.1k per 1kWp in panels + €1K per 2.0kWh in battery + €500 (diverter/Eddi) = Rough price to pay. 

I modified it a little based on price hikes over the past 12 months. It's worth noting that this is only a guideline. Guideline. If you are quoted withing a few hundred euros, that's fine. If you are being quoted (literally) €1000's more, then it's time to get another quote.

You have two types of inverters. Standard and hybrid. You need a hybrid inverter if you want to have a battery and hybrids are a little more expensive. If you don't get a battery and never plan on getting one, then you can go without a hybrid. That said, I think 80% of people would gain benifit from a battery. Forget FIT (feed-in-tarrif), and if you go for a standard hybrid inverter, you can't at a later stage add a battery.

I'm wondering what would be the use case for not getting a battery? If you can generate more power than you need at any given time, why not store it in a battery until you do need it, when it's dark or cloudy? Yes, you can in theory sell the excess back to the grid if you don't have a battery, but you'll still need to buy power back yourself (at a much higher higher cost than what you sold it for), when it's dark or cloudy. Yes, you might save €3,000 for a 6kWh battery, but you'll end up paying way more for "wasted" electricity you've bought back over the lifetime of the battery. Or am I missing something?

I guess the answer is "it depends". I mean, 3 years ago, I would have said we'd definitely need a battery to justify having solar at all: nobody in the house during the day, so minimal power use. Everyone arriving in between 4pm and 7pm, showers, cooking, TV, computers, charging phones, kettles. Six months of the year, there'd be no solar being generated at those times. Diesel car.

3 years on: Most people at home most of the day (working from home), most days of the week, so power being used constantly for computers, some lights, maybe cooking at lunchtime or a slow cooker going for a few hours. Nothing heavy, but it mounds up. So theoretically less need for a battery, but now we're also looking a) massively higher electricity bills; b) next car being a plug-in hybrid or full EV, which would be charging overnight. €300/year saving needed to break even on the battery, but my electricity bill last month was €220 - compared to one in December 2020 which was €120! I think the battery will definitely save me more than €300/year!

It's a good question that .... reasons to not get a battery. It's been addressed a few times, but never directly. There are actually some (legitimate) reasons why you wouldn't get a battery. The easy one that springs to mind is if you have a small roof. You may only have 5-6 panels - let's call it 2.5kwp. With most house loads being 500watts or there abouts (it does differ of course), you may not have enough "excess" over your base load to fill a battery regularly enough to make it worthwhile in outlaying €1500 for even a small 2.5kwhr battery. If you are in the house for example, you could simply turn on the washing machine and that would soak up most of your excess that day negating the need for a battery.

The bigger installations, the 5Kwp and above, it becomes more economical as you can more easily fill batteries as you have greater excess over base load, and it becomes lucrative to "load shift", charge it up at night time and then use those units during the day. I save about €1/day alone doing this on a 8.2Kwhr battery.

Overall, batteries are something which (in general) are to be recommended. You definitely need to do your sums though - last thing you want is to over spend on the price or buy a battery which is too big. These will take 15-20 years to payback, if at all.

That makes a lot of sense, though I would add in to look at expected future use. We can't plan for things like COVID (nobody in the house during the day -> everyone in the house during the day) but I do know that within 5 years, my car will require a plug.

Does the system need to be wired to the fuseboard or meter box or both?

My fuseboard may be difficult to get to from the attic.

I may have to look into this as it's an old stone building with the fuseboard in a separate single storey extension.

Hi Bit of a solar dummy here - though I've read a lot of the threads so definitely less so. Appreciate the knowledge. Got an annual usage around 2.5 -3kWH but have a new EV so with home charging we can expect that to increase. Working patterns are hard to predict currently but likely some home working will continue. Though I'm thinking a (modest sized) battery will still be a good long term option as there's always a lot of evening electric usage. I know there's the argument that an EV might replace a battery but as we just had a bit of an inheritance we can afford to install a good system as an investment in both financial and more general sustainability sense. House is more or less north/south so front of the house gets plenty of sun.

So is this the thread where I ask about PMs of reputable suppliers (I'm in Dublin) so I can get to the next stage? Hints appreciated.

Thanks. I wasn't sure if that was just for when you already have a quote.

You should be fine with 4 panels. I can't remember if it's the Open circuit (OC) or the loading one that matters, but I'm reasonably sure it's the open circuit and if the startup is 120v, then your well covered with 4x40volts.

As for how it performs on a cloudy day. That is very much how long is a piece of string type question. Typically though on an overcast day (no sun, but the sky is bright) you might get 20% of your rated capacity. On a dark wet day.......5-10%. None of that affects startup voltage. The amount of power which is taken from the panels is driven by the amps, not the voltage.

If your worry is can you run 4 panels.....you should be fine mate (I've 4 panels myself on a string and the startup voltage is also 120v - and I get production, as limited as it sometimes is, on wet overcast days too no problem)

Actually found this article that seems quite helpful, need to do some calculations though!

https://www.cedgreentech.com/article/solar-inverter-string-design-calculations

Sorry if it's a silly question, when you're getting providers out for quotes do they charge you for the survey/quote?

I have a Solis single phase inverter "A.C Coupled Inverter" connected to my battery storage (pylontech).

For some reason it has no Generation input (I have 4 microinvertors) and I'm having trouble figuring out the m.ginlong.com reports / APP because daily figures do not match the Eddi / Harvi data and the ESB Bill. Is there anyone who has solved this crux as my supplier is no help.