Marstek Energy brought its 3 kW, 5 kWh Venus E 4.0 residential storage system to Solar & Storage Live UK in Birmingham, where pv magazine examined the plug-in unit1. The Chinese manufacturer said the 5 kWh model is its initial focus for the UK market1.
The system combines 5,024 Wh of lithium iron phosphate (LiFePO4) battery storage with 3 kVA grid-connected charging and discharging capability, and can also provide 3 kVA of off-grid output1. Marstek says it can deliver up to 3.6 kVA of peak backup power for 10 seconds, allowing homeowners to maintain essential loads during power outages1. The company claims a cycle life exceeding 10,000 cycles at 25 C, with an 88% depth of discharge and efficiency above 90% across the battery and AC cycle1.
Designed for outdoor deployment, the Venus E 4.0 carries an IP65 rating and operates in temperatures ranging from -20 C to +60 C1. It measures 520 mm x 430 mm x 191.2 mm, weighs 47.2 kg and uses natural convection cooling rather than active fans, with DC II and AC III overvoltage protection categories1. It supports Bluetooth, Wi-Fi, LAN, RS485, MQTT and cloud-to-cloud communications, which Marstek says are intended to support integration with energy management systems and dynamic tariff platforms1.
The base unit offers 5 kWh, and Marstek says the platform can be expanded through parallel operation to provide up to 15 kWh of storage capacity and 9 kW of power output using its SmartBox solution1. The wider plug-in range includes the 2 kWh Venus E Mini and the 10 kWh Venus E Max1.
"The Venus E series has already arrived in the UK through our local distribution network. Our initial focus is on the Venus E 5 kWh system, which we believe is a strong fit for the market."
Jiang said the company is working on deeper integration with Octopus Energy and other energy management providers, to allow homeowners to optimise charging and discharging around dynamic electricity pricing1. Marstek manufactures key system components in-house, including battery cells, inverters, battery management systems and software, and says it has achieved significant penetration in Germany, France, Poland, Ukraine and the Benelux countries1.
| Specification | Figure |
|---|---|
| Battery capacity | 5,024 Wh LiFePO4 |
| Grid-connected charge and discharge | 3 kVA |
| Off-grid output | 3 kVA |
| Peak backup power | 3.6 kVA for 10 seconds |
| Claimed cycle life | Over 10,000 cycles at 25 C |
| Depth of discharge | 88% |
| Efficiency | Above 90% across battery and AC cycle |
| Ingress protection | IP65 |
| Operating temperature | -20 C to +60 C |
| Dimensions | 520 mm x 430 mm x 191.2 mm |
| Weight | 47.2 kg |
| Maximum expansion | 15 kWh and 9 kW with SmartBox |
Why it matters for households
Plug-in storage is a different proposition from a fixed home battery wired in by an installer: the unit is designed to be connected without major works, and the Venus E 4.0 is built for outdoor siting with an IP65 rating1. For a household, the practical value sits in two places. One is storing cheap off-peak or solar electricity for later use, which the communications options and the stated work with energy management providers are aimed at supporting1. The other is resilience: the unit's off-grid output and short-term peak backup are described as allowing essential loads to be maintained during power outages1. How that compares with a permanently installed system is covered in our guide to battery storage during a power cut.
The regulatory position is the constraint. UK regulations for plug-in solar introduced in August did not include plug-in battery products, and the UK government has since launched a tender for a technical risk and safety assessment of plug-in battery products to inform future regulations1. Jiang said the deployment of plug-in battery products is currently influenced by UK regulations, which do not yet fully accommodate this type of solution1. Our guide to plug-in and balcony battery storage in the UK sets out where that leaves buyers, and Marstek's own range sits alongside other home battery manufacturers in the market.
What happens next
The government tender for a technical risk and safety assessment of plug-in battery products is intended to inform future regulations1. Jiang said that once UK regulations evolve to accommodate plug-in battery systems more fully, the company believes the market will expand rapidly1. No date has been reported for the outcome of that assessment, and no UK price or on-sale date for the Venus E 4.0 has been reported1.