Solar on roof of house

All About PV Solar Panels Last Updated: 24th June 2022


If you're looking for ways to reduce your electricity bills and carbon footprint, or would like to get a better understanding of solar panels in general - this page will guide you through all you need to know, as well as the benefits of solar panels and how they work.

What are PV Solar panels?

PV Solar panels, also know as PhotoVoltaic solar panel or electric solar panels, are the type of solar panels that produce electricity. When daylight hits the panels, they will begin to start producing electricity.

There is another, older type called thermal solar panels. These make hot water directly, and are the type that were most commonly fitted 10-years old. They are much less popular in Ireland now due to the huge price drop in PV solar panels and their lower maintenance. The electricity generated from PV panels can be used to produce hot water as well as using the electricity directly, giving you the best of both. Follow this link for a Solar PV vs Solar Thermal comparison.

How much electricity do solar panels produce in Ireland?

Peak production (in kWp, or kilowatts)

Most PV solar panel systems are quoted in kW peak (or kWp). If someone talks about a 3.5kW system, that's the peak production their solar panel could generate in perfect lab conditions. Realistically in Ireland, your solar panels might top out at about 90%-95% of this in the middle of a perfect summer's day.

Annual Production

Most of us are more concerned with the total number of units of electricity produced over a year though.

1kWp of solar panels in Ireland will generate about 860 units (kWh) of electricity per year. This is for a typical Irish house somewhere in the middle of Ireland.

Here's how that works for average house sizes:

Typical Two Bed Mid-Terrace House
  • Solar Array Size: 3.4kWp
  • Roof Area Covered: 15.7m2
  • Annual Generation: 2,964kWh (units of electricity)
Typical Three Bed Semi-Detached House
  • Solar Array Size: 4.25kWp
  • Roof Area Covered: 19.6m2
  • Annual Generation: 3,724kWh (units of electricity)
Typical Four Bed Stand-Alone House
  • Solar Array Size: 5.1kWp
  • Roof Area Covered: 23.5m2
  • Annual Generation: 4,715kWh (units of electricity)
Typical Six Bed Stand-Alone House
  • Solar Array Size: 6.8kWp
  • Roof Area Covered: 31.4m2
  • Annual Generation: 5,915kWh (units of electricity)

The above are numbers for a typical house with a south-facing roof somewhere in the middle of Ireland. If your roof faces south-east or south-west, then production will be about 5% lower, and for east / west facing roofs about 20% lower.

Please note these are back of envelope numbers to give you a rough guide. In any quote we'll give you more accurate numbers for your home.

Which direction is best for solar - East / South / West?

Due South: most power output

A south-facing roof will produce the most electricity. Being a bit off directly south though has minimal impact on production. Anywhere between south-east and south-west will be very similar.

South East / South West: 5% Lower

If your roof faces south-east, or south-west, then your production will be a little lower. The timing of your electricity production will change too. South east produces more in the morning, and south west more in the afternoon / evening.

East / West: 20% Lower, but more useful?

If your roof faces due east, or due west, the production will be about 20% lower than a south-facing roof.

The production numbers though are still very good and make a savvy financial investment. There's a side benefit to east / west facing solar arrays, as they produce the most electricity when you need it most.

Most homes use their largest amount of electricity in the morning (when east facing panels are producing), and late/afternoon evening (when west facing panels are producing), as people turn on their kettles, showers and ovens.

There's a good argument for east / west facing arrays as it means less need for battery storage as you can use the power directly. You could also cover both sides of your roof as both are pointing in a useful direction.

Northerly: not worthwhile in Ireland

As you move to pointing north the production from solar panels rapidly drops off, and we would not recommend it as a good financial or carbon-footprint reducing investment.

Do solar panels work on cloudy days?

Yes is the short answer. Solar panels will produce electricity in all weather conditions including on cloudy or rainy days.

Their production is impacted though by heavy clouds. Light hazy clouds have a small impact. Days that have those thick black clouds that keep the whole day dark can have a significant impact though, perhaps reducing electricity output from the panels by up to 40%-50% on the worst days compared to a perfect blue-sky day.

Here is a graph of a month's production from a domestic solar installation in Cork (that's May 2022, which had fairly changeable weather). You can see here that during the month there were three days of particularly bad weather with significant drops in output from the solar panels due to heavy black clouds. On the other days you can see a small variance due to normal weather patterns with lighter clouds.

Graph showing fluctuations of solar energy production due to clouds
How clouds affect solar panel production here in Ireland
Clouds and weather are calculated into our quotes

When we generate quotes for solar installations in Ireland, we factor in the weather for the region which you are in. This includes the normal weather patterns including cloudy and wet days. We use the sunshine data from the nearest weather station to your home. (So yes, quotes in the sunny south-east for places like Waterford, Wexford, Kilkenny and alike have slightly higher production figures than the same installation in a cloudier part of the country!) This means the predicted generation figures on your solar quote should be about right for real world conditions.

How big are electric solar panels?

They do vary in size, but most PV panels that are fitted to houses in Ireland are 1.5 to 1.8m long, and 1 to 1.2m wide.

Roof area needed

Most panels fitted these days will have a peak production of about 210W per m2. So, if someone gives you a quote for a 3kWp solar panel system on your house, then it will probably cover 14.3m2 of your roof.

How do solar PV panels work?

When daylight strikes the solar panels, there is a movement of electrons within the cell. This activity creates an electrical voltage. This voltage is collected by conductors, and then connected to output cables. (If you want to get really nerdy and understand the science behind how solar panels work, you can read our article here. )

The electricity is a DC voltage, similar to that in a car battery. This voltage then travels through solar PV cables, into an inverter in the attic. The inverter changes or converted the DC electricity into AC electricity.

What are the benefits of solar PV Panels?

Below is some information on the benefits of installing solar PV panels.

  • Reliable Energy Source - With the sun as its primary fuel source, solar energy will be accessible for the next 5 billion years.

  • Reduces Electricity Bills - Solar PV is a proven technology, and will result in a lowering of your electricity bills.

  • Government incentives - At the moment there are grants of up to €2400 for installing solar PV panels. In the summer of 2022, there will be a Clean Export Guarantee payment available to households that install solar PV.

  • Low Maintenance - Solar PV panels have no moving parts. Therefore there is very little maintenance required except cleaning them the rare time the rain doesn't clear off any debris.

  • Future Proof - Installing solar PV is a way of protecting yourself against rising electricity prices.

What are the disadvantages of solar PV panels?

Solar isn't for everyone and isn't suited to all homes, check out below, some disadvantages.

  • Cost - While the cost of owning a solar PV system has come down substantially over the past number of years, the initial upfront investment is considerable.

    Unfortunately, energy-poor households, that would benefit substantially from solar energy, are a stretch too far economically.

  • Weather - Although solar energy can perform during cloudy and rainy days, the efficiency of the solar system drops.

  • Battery storage is expensive - Electricity generated from solar energy needs to be used straight away, or it will be lost back to the grid. A way of ensuring you maximise the full usage of your solar panels is by storing the surplus energy in batteries.

  • Space - Solar PV panels require a lot of space, and some roofs don't have enough. The more electricity you want to harness, the more solar PV panels are required to collect as much solar energy as possible.

What are the costs of installing solar PV panels?

The cost of solar panels is dependent on your electricity usage, in terms of how much you are spending on electricity monthly. Your roof space also determines how many solar panels you can install. This in turn will determine the cost of your solar panels.

Also, the costs of solar panels are also determined by the installer. It is always a good idea to get a minimum of three quotes from different installers.

For more information we have a full guide to solar panel prices in Ireland which includes prices, payback, electricity production forecasts and carbon-footprint reduction numbers.

Are solar panels environmentally friendly?

Yes indeed they are. Solar energy is one of the cleanest forms of energy on earth. Solar PV doesn't use water to operate or release any harmful chemicals or substances.

The carbon footprint of an average solar photovoltaic (PV) system is between 14-73 grams of carbon dioxide equivalent (CO2e) per kilowatt-hour (kWh).

Although this sounds like a lot for a renewable energy source, it's relatively low compared to the average emissions of burning oil - 742g of CO2e per kWh.

How long do solar panels last?

Solar panels are designed to last up to 25 years. Many solar manufacturers have warranties that are up to 30 years. The 25-30 year warranty does not mean that they will give up after this period. It means the manufacturer will guarantee their output for this time.

It's more than likely that the solar panels will still produce energy after 30 years. But, with possible degradation of generation output.

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