MCS, the UK certification scheme for small-scale renewable installations, is consulting on its first product standard for battery storage. The draft, MCS 042, covers home and small commercial batteries. As ESS News reported on 30 October 2026, it could bring IoT cybersecurity requirements into the certification that battery makers need to sell through MCS-certified installers. Comments are open until 11:59pm UK time on 10 November 2026.

Why MCS wants a product standard

Battery storage has been part of MCS installer certification since 2021, but that covers the installation, not the product. Solar panels already have to meet an MCS product standard, and batteries have no equivalent. MCS says batteries are now its fastest-growing technology, with more than 60,000 installed in UK homes and small businesses in 2026 by the end of September. That is already over 50% more than last year's record total.

The draft was written by MCS's Battery Storage Technical Working Group, which includes installers, manufacturers, trade associations and certification bodies. The Energy Storage Association (ESA), which supports the standard, told ESS News that many batteries on the UK market would probably comply already.

Cybersecurity for connected batteries

The part that matters most for smart home owners is cybersecurity. According to ESS News, connected components would have to meet ETSI EN 303 645, the European baseline standard for consumer IoT security. The baseline requirements under discussion include:

  • no default passwords
  • secure software updates
  • vulnerability management
  • secure communication between the battery, the inverter and any cloud platform or mobile app

Products with Wi-Fi, Bluetooth or another radio would also have to meet BS EN 18031, the standard linked to the radio equipment rules. Integrated battery and inverter units would need BS EN 62477-1 for power electronics and IEC 61000 for electromagnetic compatibility.

Safety and honest specifications

The proposed minimum safety requirements are IEC 62619:2022 for lithium cells and batteries and UN 38.3 for transport. The standard would apply to AC-coupled systems with the battery and inverter in one enclosure or in several close-coupled enclosures, and to DC-coupled battery packs with or without their own battery management system.

Manufacturers may also have to declare a set of performance figures: nominal energy capacity, input and output power, round-trip efficiency and expected service life. If part of the nominal capacity cannot be used in normal operation, they would also have to state the usable capacity, which would make comparing spec sheets easier.

What happens next

MCS has not given an implementation date yet. Installers will get a transition period until an "adequate number" of certified products is on the market. If the draft passes in this form, a battery certified under MCS 042 should come without a shared default password and with a documented way to get security fixes.