Solar Panels and Home Batteries: A Beginner’s Guide

A lot of neighbours have started talking about solar panels. For some it's the price of electricity, which doesn't look like it's coming down any time soon. For others it's the storms — after a few winters of red warnings and power cuts, the idea of keeping the fridge and the Wi‑Fi going when the rest of the road is dark is appealing.

If you know next to nothing about solar, this is the place to start. It won't tell you which company to use, but it should mean you understand what an installer is telling you, ask the right questions, and don't end up paying for something that doesn't do what you assumed it would. (The big one: most solar systems switch off during a power cut. More on that below.)

The basics in two minutes

A home solar system has three or four parts:

• Panels on the roof turn daylight into electricity. They work on cloudy days too, just less well — and they produce nothing at night.
• An inverter is a box, usually in the attic or garage, that converts what the panels make into the kind of electricity your sockets use.
• A battery (optional) stores electricity you don't use straight away, so you can use it later — in the evening, say.
• Your smart meter records what you take from the grid and what you send back to it.

Through the day, your house uses solar first. If the panels make more than you need, the extra goes into the battery (if you have one) and then out to the grid, where your supplier pays you for it. When the panels can't keep up — evenings, winter, the kettle and the oven going at once — you draw from the battery and then from the grid, exactly as you do now. You never "run out" of electricity; the grid is always there in the background.

kW vs kWh — the one bit of jargon worth learning

You'll see both everywhere, and they're easy to mix up:

• kWh (kilowatt-hour) is an amount of energy — it's the "unit" on your electricity bill. Think of it like litres of water.
• kW (kilowatt) is how fast power is made or used at a given moment — like how fast the tap is running.
• kWp ("kilowatt peak") is how installers describe a set of panels: the most it can produce in ideal sunshine. A "4 kWp system" is the size of the panel setup, not how much it makes in a year.

Batteries are sized in kWh (how much they hold), inverters in kW (how much they can deliver at once).

Step 1: Work out how much electricity you actually use

Before anyone can tell you how many panels or how big a battery you need, you need to know your own usage. Two ways:

The quick way: your bills

Add up the units (kWh) on your last 12 months of bills, or look for an annual figure on your supplier's app. For comparison, the CRU (the energy regulator) puts the average Irish household at about 4,200 kWh a year. Don't be surprised if you're well above that: our houses are heated by an electric heat pump rather than gas or oil, so your heating and hot water are on your electricity bill too — and in winter the heat pump can use more than everything else in the house combined. An electric car adds a lot on top.

The better way: your half-hourly data from ESB Networks

Our houses have smart meters, which record your usage every 30 minutes. That detail matters: a battery is only useful if it fits when you use electricity, not just how much. You can download it for free:

1. Register at myaccount.esbnetworks.ie. You'll need your MPRN (the 11-digit number on your electricity bill) and the phone number your supplier has on file. You must be the named account holder.
2. Log in and choose My energy consumption.
3. Go to the Downloads tab and download "30 Minute Readings in kW" as a CSV file.

ESB Networks keeps up to two years of readings, even if you've switched supplier in the meantime. If you've only just moved in, it can take up to a month before data appears.

Turning that data into an answer

homebattery.ie is a free tool, made by one of our neighbours, built exactly for this. You upload the ESB Networks file (don't open it in Excel first — that can scramble the dates) and tell it the size and direction of the solar you're considering. It then:

• suggests a few battery sizes — one to soak up your solar surplus, one to cover most of your day from a cheap overnight charge, and one best suited to your tariff;
• estimates what you'd save and roughly how long the system would take to pay for itself;
• compares smart and EV tariffs against your real usage.

Its cost figures are placeholders, so swap in the prices from your actual quotes. It's a good way to walk into a conversation with an installer already knowing roughly what makes sense for your house.

Step 2: How many panels?

There's no single right answer, but here's how to think about it.

What a panel makes here: County Wicklow is one of the sunnier parts of Ireland. Published estimates put it at roughly 950 kWh a year for every 1 kWp of panels on a south-facing roof. Modern panels are around 430–500 watts each, so:

Treat those as ballpark figures. East- or west-facing roofs produce somewhat less (though panels on both sides spread the output across the morning and evening, which some people prefer). Shading from a tree or neighbouring roof matters more than you'd think.

The seasons matter a lot. Most of that yearly total arrives between April and September. In December and January even a big system makes very little. So solar won't wipe out your winter bills — it takes a big bite out of spring and summer ones.

A sensible starting point: size the panels so that, over a year, they make somewhere around what your house uses in daylight hours plus what a battery can store for the evening. Going much bigger than that mostly means exporting more to the grid — which you do get paid for, but at a lower rate than you pay to buy electricity back.

The practical limit: most homes are on a single-phase supply, and the standard ESB Networks sign-off (the NC6 form, which your installer submits) covers systems up to about 6 kW of inverter size. In practice, most home inverters installed in Ireland are 5.5 kW, which sits comfortably under that limit — so that's the figure you'll most often see on quotes, and most home systems land somewhere between 3 and 6 kWp of panels. Going bigger needs a separate application to ESB Networks, so ask your installer before planning something larger.

What is "clipping"?

You may hear an installer suggest putting, say, 6.5 kWp of panels on a 5.5 kW inverter, and mention that the system will "clip". That sounds like a mistake, but it's usually deliberate.

The inverter can only pass on so much power at once — a 5.5 kW inverter tops out at 5.5 kW. If the panels are ever producing more than that, the extra is simply lost: the output gets "clipped" flat at the inverter's limit, like water spilling over the top of a full glass.

In Ireland, that rarely happens. Panels only reach their full rated output in strong, direct sun — a few hours on the brightest summer days — and most of the year they produce well below it. So a slightly bigger set of panels loses a little on those peak days, but makes noticeably more in the mornings, evenings, cloudy days and winter, when it counts. Having somewhat more panel than inverter is common practice for that reason.

What to watch for: a small amount of clipping is fine; a lot means you've paid for panels whose output you'll regularly throw away. If a quote has much more panel (kWp) than inverter (kW), ask the installer how much they expect to lose to clipping over a year. Note that a battery charged directly from the panels (a "DC-coupled" setup) can sometimes catch some of that extra — another thing worth asking about.

Step 3: Do you need a battery?

No — panels work perfectly well on their own. But a battery changes how much of your solar you actually get to use yourself.

Without a battery, you use solar only while it's being made. If everyone's out at work during the day, much of it goes to the grid, and you buy electricity back in the evening at a higher price than you were paid for it.

With a battery, that daytime surplus is stored and used in the evening, when most houses use the most electricity.

A battery can also help in other ways:

• Charging from the grid overnight. With a smart or night-rate tariff, the battery can fill up on cheap night electricity and run the house through the more expensive day and evening. This works even in winter, when there's little sun — for some households it's where most of the battery's savings come from. The Electricity Suppliers in Ireland article explains the tariff types.
• Backup in a power cut — but only if the system is set up for it. See the next section.

The downsides: a battery adds a significant chunk to the cost, and like a phone battery it slowly loses capacity over the years. Whether it's worth it depends on your usage pattern, your tariff, and how much the power-cut backup is worth to you. That's exactly the question homebattery.ie is designed to answer from your own data.

Rough prices, for context only: Irish guides published this year put a 4 kWp panel system at somewhere between about €6,000 and €10,000 installed, and a battery at roughly €2,000 to €7,000 depending on size. Quotes vary widely, so get several.

Will a battery keep the lights on in a power cut?

This is the part that catches people out.

By default, no. When the grid goes down, a standard solar system shuts itself off automatically — even on a sunny day, and even with a full battery. It's a legal safety requirement: if your panels kept pushing electricity out into the street's cables, they could electrocute the ESB crew working to fix the fault. Installers call this anti-islanding.

To have backup power, your system needs to be able to disconnect your house from the grid completely and run off the battery (and panels) on its own. That needs:

• A hybrid inverter with a backup output — often labelled EPS (Emergency Power Supply) or "backup". Not every inverter has one, and on some it's limited to a single socket.
• A changeover switch — the device that physically separates your house from the grid during an outage and connects it to the battery instead, then back again when the power returns. It's what makes it impossible to send electricity back out onto the street's lines. It comes in two kinds:
  • Manual: when the power goes, you go to the switch and flip it over yourself. Cheaper and simple, but the house stays dark until you do.
  • Automatic: it detects the outage and switches over on its own within seconds (some setups are near-seamless). More expensive, but nothing to do in the middle of the night.
• Usually, an "essential loads" circuit or board. A home battery can't run the whole house at full tilt. Typically you choose a handful of circuits to keep going — fridge and freezer, lights, Wi‑Fi, phone charging. Big loads like an electric shower, the oven or the heat pump are usually left off, so plan on the heating being off during an outage.

How long would it last? That depends on the battery size and what's running. A fridge, some lights and the router use very little and can run for a long time from a typical home battery; add a kettle and a TV and it drains much faster. On a sunny day the panels can top it back up while the grid is still down.

Because this is fixed wiring at your fuse board, it has to be designed and installed by a registered electrician — see Electrical Work in Your House: What Needs a Certificate.

If backup is a big part of why you want solar, say so at the very start. Ask every installer, in writing: "Will this system power my house during a power cut? Which circuits? Is the changeover manual or automatic?" It's much cheaper to design in from day one than to add afterwards.

The SEAI grant — why it doesn't apply to us

The SEAI Solar Electricity Grant (worth up to €1,800) is only available for homes built and occupied before 2021. Hawk's Bay houses were built after that, so we don't qualify. It's aimed at bringing older houses up to standard, not newer ones.

In practice, this just means that when you see solar ads quoting "€X after grant", you need to add the grant back on to get your real price. Always ask for quotes without the grant.

A couple of things do still work in our favour:

• 0% VAT. Solar panels supplied and installed on homes are zero-rated for VAT, so this should already be reflected in any quote.
• No planning permission. Since October 2022, rooftop solar on houses is exempt from planning permission almost everywhere, with no limit on how much of the roof you cover (the panels need to sit close to the roof and at least 50 cm in from the edge — any competent installer will handle this).

Getting paid for what you send to the grid

Any electricity you export is paid for by your supplier under the Clean Export Guarantee. Once your installer has submitted the NC6 form, ESB Networks registers your system and your supplier starts crediting your bill for what you export. Rates vary by supplier and change often — this year they range from about 13c to 25c per unit — so check before you choose. The first €400 a year of export income is currently tax-free.

It's worth remembering that exporting pays less than buying: using your own solar electricity is almost always worth more to you than selling it.

A few practical tips

• Get at least three quotes, all for the same thing, and all without the grant. Compare panel count and size (kWp), battery size (kWh), inverter make, whether backup is included, and the warranties.
• Use an SEAI-registered installer anyway. We can't get the grant, but the registration means they've met SEAI's standards, and the electrical side must legally be done by a Safe Electric registered electrician who gives you a completion certificate.
• Ask about your roof warranty. Our houses are only a couple of years old. Before anyone drills through the roof, ask the installer how they fix the panels and whether it affects any roof or HomeBond cover — and get their workmanship warranty in writing.
• Ask about bird mesh. Pigeons love nesting under solar panels. Mesh around the edges is cheap to add at install time and a pain to add later.
• Make sure you get a monitoring app. Most inverters come with one that shows what you're generating, using and storing. It's the easiest way to spot if something stops working.
• Tell your home insurer once the system is in — it adds value to the house and should be covered.
• Compare notes with neighbours. With so many of us looking at this at once, it's worth asking on the Noticeboard who's already had it done, what they paid, and how they found the installer. Similar houses with similar roofs means a neighbour's real-world results are probably the best guide you'll get.

Compiled from publicly available SEAI, ESB Networks, CRU and industry information — not an endorsement of any particular company, and not a substitute for advice from a qualified installer. Prices and export rates are as of autumn 2026 and change often. If you spot outdated details here, let a committee member know so we can update this page.