How Emergency Power Supply (EPS) Works on Hybrid Inverters

When the grid goes down, a hybrid inverter with Emergency Power Supply (EPS) can keep selected circuits running from stored battery energy, usually switching over within a matter of milliseconds. This is one of the most asked-about features among homeowners and installers researching a SolaX hybrid inverter in Essex, and it is worth understanding properly before choosing a system, since not every hybrid inverter offers true EPS, and not every EPS setup covers the whole house.

What EPS Actually Does

EPS is not the same as simply having a battery. A hybrid inverter constantly monitors the grid connection. If it detects a loss of grid supply, whether from a local fault, storm damage, or scheduled network maintenance, the inverter isolates the property from the grid and reroutes power from the connected battery to a dedicated EPS circuit.

This isolation is essential for safety, since it prevents the system from feeding electricity back into a grid that engineers may be working on.

Most SolaX Power inverters sold for domestic use in Essex handle this switch automatically, with no need for manual intervention. The changeover is quick enough that most electronics, lights, and routers do not reset. Some appliances with compressors or motors may briefly restart.

How the Switch-Over Works, Step by Step

• Grid monitoring: The inverter continuously checks voltage and frequency on the incoming grid supply.
• Fault detection: If the grid supply drops out or falls outside safe parameters, the inverter registers this within milliseconds.
• Isolation: The inverter disconnects the property from the grid to prevent backfeed, satisfying UK electrical safety requirements for grid-tied systems.
• EPS activation: Power stored in the connected battery is directed to the EPS output, typically a separate consumer unit or specific circuits wired in at installation.
• Restoration: Once grid power returns and stabilises, the inverter reconnects automatically and resumes normal hybrid operation.

What EPS Can and Cannot Power

This is where expectations often need managing. EPS is generally designed to support essential loads rather than an entire household during an extended outage. Typical EPS setups cover the following:

• Lighting circuits
• Broadband router and telecoms equipment
• Fridge and freezer
• A small number of sockets for phone charging or essential devices

High-draw appliances such as electric showers, ovens, or air conditioning units are usually excluded, since running them on stored battery power would drain capacity quickly and may exceed the EPS circuit’s rated output. The exact circuits covered depend entirely on how the installer wires the EPS panel at the point of installation, so this is a conversation worth having before the system goes in, not after.

Battery Capacity and How Long EPS Will Last

How long EPS power lasts depends on the usable capacity of the connected battery and the number of circuits wired into the EPS panel. A modest domestic battery running only lighting, a router, and a fridge can often provide backup for hours, while running higher-draw devices will shorten that considerably. Furthermore, solar input during a daytime outage can extend runtime further, since the panels continue to charge the battery even while the grid is down.

Why Emergency Power Supply Systems Are Worth It for Essex Homes

Essex has its share of rural and semi-rural properties where grid outages, whether from storms, tree damage, or planned works, are not unusual. For these households, EPS-equipped hybrid inverters offer a practical layer of resilience beyond standard solar generation. It is one of the reasons Eco Angels receives regular enquiries about SolaX hybrid inverter options from both homeowners and installers across the county.

Getting EPS Set Up Correctly

EPS performance depends heavily on correct installation, from the sizing of the EPS circuit to the placement of the changeover panel. Eco Angels supplies SolaX Power inverters and Triple Power battery modules to trade customers and installers across Essex and London, alongside guidance on matching inverter and battery specifications to a property’s needs. Anyone planning a new installation or considering an upgrade is welcome to get in touch with our team to talk through the options.

Frequently Asked Questions