What is DC Isolator?
A safety switch that disconnects the DC supply between the solar panels and the inverter.
Quick Answer
DC isolators are mandatory on UK solar installations and must be fitted by an MCS-certified installer to meet wiring regulations. Older rooftop DC isolators were a known weak point and occasional fire risk if water got in, so many modern installs use better-rated or relocated isolators. If you have an older system, it is worth having the isolator checked during maintenance.
Fact-checked by John Rooney, Solar Energy Editor. Editorial policy
DC Isolator Explained
A DC isolator is a switch that lets the DC power from the solar panels be safely disconnected from the inverter, for example during maintenance or an emergency. Because solar panels generate voltage whenever there is light, a DC isolator is essential for safely working on a system. UK installations require both a DC isolator (on the panel side of the inverter) and an AC isolator (on the mains side). Faulty or poorly installed DC isolators have historically been a cause of solar system faults, so quality and correct fitting matter.
How Does DC Isolator Work in the UK?
DC isolators are mandatory on UK solar installations and must be fitted by an MCS-certified installer to meet wiring regulations. Older rooftop DC isolators were a known weak point and occasional fire risk if water got in, so many modern installs use better-rated or relocated isolators. If you have an older system, it is worth having the isolator checked during maintenance.
Frequently Asked Questions
What does a DC isolator do?
A DC isolator is a safety switch that disconnects the DC power coming from the solar panels to the inverter. Because panels generate voltage in any light, it lets the system be safely isolated for maintenance or emergencies. UK installs need both a DC isolator and an AC isolator.
Are DC isolators a fire risk?
Older rooftop DC isolators were a known weak point and could pose a fire risk if water ingress caused corrosion. Modern installations use better-rated or better-positioned isolators. If you have an older system, have the DC isolator inspected during routine maintenance.
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John Rooney is the founder of Solar Info and has been covering the UK solar energy market since 2023. He researches every battery and inverter brand against manufacturer datasheets, MCS and Ofgem data, and feedback from the MCS-certified installers in our directory before publishing.