A solar PV system has a few main parts, and the right combination depends on your home, your roof and how you use electricity. This guide explains the basics so you can ask better questions. It is educational information, not a formal technical assessment.
The main parts
- Solar panels turn daylight into electricity. System size is measured in kWp (kilowatts peak), which is the number of panels multiplied by each panel’s wattage. Ten 400 W panels, for example, make a system of about 4 kWp.
- An inverter converts the panels’ direct current into the alternating current your home uses. Inverters are rated in kW. Some are hybrid inverters, designed to work with a battery now or later.
- A battery (optional) stores spare solar electricity for later. See our battery storage advice.
- A hot water diverter (optional) sends spare solar power to your immersion heater, if you have a suitable hot water tank.
What affects the right size
- How much electricity you use, and when. Look at your bills and your daily routine.
- Your roof: its direction, tilt, shading and available space. South-facing roofs generally produce the most, but east and west roofs can work well too.
- Your electrical supply. Single-phase and three-phase homes have different options, and connection to the grid needs ESB Networks approval.
- Your budget and grant support. The standard SEAI grant is based on system size up to 4 kWp. See our solar grants guide.
Bigger is not always better
SEAI has noted that a system of about 2 kW is a good fit for high self-consumption in an average Irish home without storage, and that larger systems benefit from some form of storage or a diverter. A bigger system may produce more, but only electricity you use in the home saves you money in the same way.
Who decides what is suitable
Solar123 can help you understand your options, but we do not survey your property. An installer must inspect your home and confirm that a system is suitable, safe and compliant before any work is agreed. Compare more than one quote using our quote comparison guide.