Solar panel & battery glossary

15 solar PV terms explained

kWp (kilowatt peak)

The peak electrical power rating of a solar panel array under standard test conditions. Ten 440W panels equal a 4.4kWp system.

kWh (kilowatt-hour)

One unit of electricity on your household bill. A 4.4kWp south-facing system in Ireland typically generates 3,600 to 4,200 kWh a year.

SEAI Solar Electricity Grant

The grant administered by the Sustainable Energy Authority of Ireland, paying €700/kWp for the first 2kWp and €200/kWp up to 4kWp (capped at €1,800).

ESB Networks NC6 form

The microgeneration connection notification submitted by your installer to ESB Networks before your solar inverter connects to the grid.

Clean Export Guarantee (CEG)

Ireland's microgeneration export tariff under which electricity suppliers pay homeowners per kWh of surplus solar power exported to the grid.

String inverter

The wall-mounted unit that converts DC electricity from a string of rooftop solar panels into 230V AC electricity for the house.

Hybrid inverter

An inverter with built-in battery management that can charge and discharge a DC home battery as well as convert solar panel power.

LFP (LiFePO4) solar battery

Lithium iron phosphate home battery chemistry (typically 5kWh to 10kWh) used to store daytime solar power for evening use.

Depth of Discharge (DoD)

The usable percentage of a solar battery's total storage capacity, usually 90% to 95% on modern LFP batteries.

Hot water diverter

A proportional controller that diverts surplus solar electricity to the immersion element in your hot water cylinder instead of exporting it.

DC isolator & fireman's switch

Safety switches fitted between the solar array and inverter to isolate high-voltage DC roof cables during maintenance or emergencies.

Roof hook & rail mounting

Stainless-steel hooks fixed to the timber rafters under slates or tiles that carry the aluminium rails holding the solar panels.

In-roof (GSE) mounting

Recessed trays that sit in place of roof tiles or slates so the solar panels lie flush with the roof surface.

DC optimiser

A module-level unit fitted behind individual panels so shading from a chimney or tree on one panel does not pull down the rest of the string.

Post-works BER

The Building Energy Rating assessment required after solar panels are installed so SEAI can verify the system and pay the grant.