Why UK Plug-In Solar Kits Can't Include Batteries

The Interim Product Specification bans batteries in the plug circuit. Here's why, and what it means for your setup.

The Rule

The DESNZ Interim Product Specification v2 explicitly prohibits battery storage in the plug circuit of a plug-in microgenerator. This means any certified kit sold from 27 August 2026 cannot include a battery that feeds electricity through the BS 1363 plug.

Why Batteries Are Excluded

Three reasons drove this decision:

1. Fire Safety

Lithium-ion batteries carry a fire risk, particularly in domestic settings. Adding a battery to a device plugged into a standard socket — potentially near curtains, furniture, or in a bedroom — creates a risk profile that regulators weren't comfortable with for a consumer-installable product.

2. Anti-Islanding Complexity

Anti-islanding protection ensures a solar system disconnects from the grid during a power cut, protecting line workers. Batteries complicate this because they can continue supplying power after panels stop generating. The safety testing regime for battery-backed anti-islanding is more complex and wasn't ready for the initial launch.

3. Regulatory Caution

The UK government chose a conservative approach for the first generation of plug-in solar. Starting without batteries allows them to gather real-world safety data before potentially relaxing the restriction.

What About the EcoFlow STREAM Battery?

The EcoFlow STREAM includes an optional 600Wh battery, but it's designed to comply with the IPS v2. The battery operates on the DC side of the system — it stores energy from the panels and manages it through the inverter, but the battery's discharge is controlled so that the plug output still meets IPS v2 safety requirements.

Whether this design passes certification is yet to be confirmed. EcoFlow has been working closely with DESNZ on compliance.

Can You Add a Battery Separately?

You can buy a separate battery storage system that charges from solar panels and discharges through a different circuit. However, this falls outside the scope of the IPS v2 and may require a qualified electrician.

For most households, maximising self-consumption through smart scheduling and load shifting is a more practical approach than adding battery storage.

Will Batteries Be Allowed in Future?

Very likely. BSI's full product standard (expected 2027) is expected to include provisions for battery-integrated systems with enhanced safety testing requirements. The government has indicated this is a "first step" approach.

What's the alternative to a battery?

Use smart home automation to shift high-consumption tasks (washing machine, dishwasher, EV charging) to peak solar hours. This achieves much of the benefit of a battery without the cost.

Does this mean EcoFlow STREAM can't be sold with its battery?

Not necessarily. If the battery operates on the DC side and doesn't feed through the plug circuit, it may comply. We'll know definitively when EcoFlow achieves certification.

How much does the no-battery rule cost me?

Without a battery, you lose some evening/night self-consumption. Realistically, a battery adds 10-20% more savings, so the impact is £20-40 per year — significant but not transformative.