Electricity from solar
Learn more about how we generate electricity from solar PV what you need to consider before making an investment.
Solar panels explained
The term 'solar panel' is often used interchangeably to describe the panels that generate electricity and those that generate hot water.
- Solar panels that produce hot water are known as solar thermal collectors or solar hot water collectors.
- Solar panels that produce electricity are known as solar photovoltaic (PV) modules. These panels generate DC electricity when exposed to light.
This page focuses on those technologies that generate electricity from light.
Solar electricity technologies
There are two broad groups of technologies which generate electricity from light. Of these, solar PV technologies are best suited for use in Ireland.
Solar photovoltaics (solar PV)
These are the most common solar technologies worldwide. They are also the fastest growing in terms of installed capacity.
Concentrated Solar Power (CSP)
These technologies produce electricity by focussing sunlight to produce heat and drive an engine connected to an electrical generator. They are currently found in countries with year round sunshine.
How Solar PV works
Certain semiconductor materials generate electricity when exposed to visible light. These are called Photovoltaic (PV) materials.
Solar PV technologies use a wide variety of semiconductor materials. The most common to date are those using silicon as the photovoltaic material. However, technologies based on other semiconductor materials are growing their market share.
Solar PV systems
A solar electric system is typically made up of:
- Solar panels on the roof, which generate DC (direct current - like in a battery)
- An 'Inverter' which converts this to AC (alternating current - like the electricity in your house socket)
- Sometimes a battery on larger systems to save energy for later use
Solar PV systems generate electricity during daylight hours only, predominately around the middle of the day. In Ireland, around 75% is produced from May to September. If this electricity is not used in the home it is exported to the grid.
It is desirable to maximise the amount of solar electricity you use in your home. You can do this by sizing the solar PV system to meet your demand.
Installing a domestic solar PV system
A domestic solar PV system consists of a number of solar panels mounted to your roof (or in your garden) and connected into the electrical loads within your building. The solar panels generate DC (direct current - like a battery) electricity, which is then converted in an inverter to AC (alternating current - like the electricity in your domestic socket). Solar PV systems are rated in kilowatts (kW). A 1kW solar PV system would require 3 or 4 solar panels on your roof.
Any excess electricity produced can be stored in a battery, or other storage solution like your hot water immersion tank. It can also be exported from your house into the electrical network on your street.
Solar PV products
Solar PV products exist for a range of different applications. These include:
- Solar panels or modules. These are the best known solar PV products. Now a familiar site on rooftops and in 'solar farms' they have been mass manufactured for over 25 years.
- Building Integrated Photovoltaics (BIPV). These are building material products such as roof tiles, glass or cladding with solar PV materials embedded within them.
- Consumer electronics. Some consumer products have been developed with solar PV materials integrated into them so that they can produce their own power.
A big share of your annual electricity needs
Conventional solar PV panels will help meet some of the electricity demands of a building.
- 1 sq. m of silicon solar panels will generate ~150W of power on a clear sunny day. That's enough to power a laptop computer.
- A home solar PV system sized at 20 sq. m (~3kW) and well located would generate around 2,600kWh of electricity a year. That is over 40% of the average annual electricity demand of an Irish home.
- Solar PV systems will still function on overcast days in Ireland although not at their maximum rated capacity.
Factors that affect electricity production
The amount of electricity a solar panel will generate depends on a range of factors. These include:
- The hardware chosen
- The size of the system
- The geographical location
- The direction in which the panels are installed
Invest in a Solar PV System
There are some important things to consider before investing in a solar PV system for your community, home, or business.
Find the right installer
Finding a competent installer is important, some installers work independently and others work with one or many registered companies. A registered installer is the only person who is allowed to declare that the solar PV installation meets the scheme requirements. A registered installer will be:
- Recognised with a Solar PV qualification
- Registered Electric Contractor (REC) with Safe Electric Ireland
- Tax compliant
- Registered on SEAI's Renewable Installers Register
Choose the right equipment
Speak to your installer about the products they offer. Solar PV systems will usually include:
- Solar modules
- An inverter, which converts electricity from direct current (DC) to alternating current (AC)
- A mounting system for the roof or ground
- Some installers also offer battery systems or 'diverter switches' for storing excess energy
Check the Triple E Register for solar PV products that meet a minimum performance criteria, including energy efficiency.
Check planning permission
Solar PV systems installed in a domestic setting that are under 12 sq. m (and represent less than 50% of the total roof area) are exempt from planning. The same exemption applies to solar PV systems in a business or industrial setting that are under 50 sq. m.
Larger solar PV systems in homes and businesses will typically require planning permission. We recommend you speak with your local planning authority to understand the requirements.
FAQs
The simplest way to use a higher percentage of the electricity generated is to design the PV system to meet the average daily electricity demand of the house, although this may mean a very small PV system is installed if demand is low during the daytime.
Another simple measure is to install a 'diverter switch' which diverts any unused electricity to heat your hot water in your immersion tank. In this way some of the energy generated is stored as hot water, which you can use later.
Finally, a more complicated option is to install a PV system which does not face south, but faces west or east. This will provide more energy in the morning or the evening when you have a greater demand to use it. However, an east- or west-facing PV system will generate less energy over the year than a south-facing system
Adding a battery to your solar PV system means the battery will charge when the PV system is generating electricity which isn't being used, and then discharge when you need it next (normally that evening/night). A battery can increase the percentage of solar PV electricity you use in your house. Adding a battery to the system will increase the cost of the PV system and some energy will be lost in the battery during the charge and discharge cycle.
Homes with PV systems that generate more energy than they consume can export that excess to the grid and benefit from payment for that exported electricity. This payment is known as the Clean Export Guarantee (CEG) and is essentially a feed-in tariff. This tariff will be paid at a 'competitive market rate' from your electricity supplier. Each supplier will set their rates so you will need to contact your electricity supplier directly for details of their CEG rates.
The CEG will be available to both new and existing micro-generators, subject to the eligibility criteria.
You will need to have a suitable ESB Networks export grid connection to avail of the CEG.
You will also need to have a smart meter installed to get paid precisely for what is exported. If you do not have a smart meter installed, you may get paid based on a deemed volume assumption determined by the CRU.
PV systems are low-maintenance, but not zero maintenance. The most important aspect is to monitor the performance of your system regularly. This could simply be a routine check of your inverter to see that the system is operational and that the energy meter is increasing each day.
You should get an idea from your installer about how much the PV system should generate each year, and see that your system is generating close to that amount. Some suppliers will provide you with access to this information via your smartphone. The most common point of failure is the inverter, which may need to be replaced at some point in the PV system's lifetime.
The solar panels themselves are extremely robust, but consideration should be given to cleaning them every few years to maintain their performance. If you live near the sea or a main road more regular cleaning may be necessary.