Home battery backup power and essential circuits

What happens during a power cut without a battery?

Everything goes off. Lights, fridge, freezer, internet, heating controls. Most UK power cuts last a few hours, but some last much longer. In winter storms, rural areas can lose power for a day or more.

A home battery changes this. When the grid drops, the battery detects the outage and switches to backup mode within milliseconds. Your essential circuits stay powered as if nothing happened.

What are essential circuits?

Essential circuits are a selected set of circuits in your home that your battery keeps powered during an outage. Your installer wires these separately so the battery can isolate and power them independently from the rest of the house.

Common choices for essential circuits include:

• Lighting for key rooms (kitchen, living room, hallway)
• Fridge and freezer so food doesn't spoil
• Internet router so you stay connected
• A few plug sockets for phone chargers, laptops, and small appliances
• Heating controls (the boiler itself uses gas, but the controller and pump need electricity)

You choose which circuits matter most to your household. Your installer sets them up during the battery installation.

How long does backup power last?

It depends on what you're powering and how much charge the battery has. Here are some realistic estimates for a fully charged 11.5kWh battery:

These are rough guides. A fridge draws very little power (around 50W on average). LED lighting is minimal. Your internet router uses about 10-15W. Together, essential circuits might draw 200-500W, which means an 11.5kWh battery lasts a long time.

High-draw appliances like kettles, ovens, and electric showers use significantly more power and will drain the battery quickly. That's why essential circuits focus on the things you actually need, not everything you have.

Can I go fully off-grid?

A single home battery is not designed for full off-grid living. Powering an entire home continuously, including electric heating, cookers, and high-draw appliances, requires significantly more storage and generation capacity than one battery provides.

For most UK homes, essential circuit backup is the practical approach. You get peace of mind during outages without the cost and complexity of a full off-grid system. If you have solar panels, the battery can recharge during the day, extending your backup even further.

Essential circuits vs. whole-home backup

How the switchover works

When the grid goes down, your battery's inverter detects the loss of power and disconnects from the grid. This is required for safety so that your battery doesn't feed electricity back into power lines that engineers may be working on.

Within milliseconds, the inverter switches to backup mode and begins powering your essential circuits from the battery. When grid power returns, the system reconnects automatically and resumes normal operation.

You don't need to do anything. The switchover is automatic.

Backup power is a bonus, not the main reason

Most people buy a home battery to save money on their electricity bill. On a time-of-use tariff like Octopus Go, an 11.5kWh battery saves £900+ per year by charging overnight at 9.5p/kWh and powering your home during the day.

Backup power during outages is a valuable bonus on top of those daily savings. You get financial benefit every single day, plus peace of mind when the grid goes down.

Backup with Habo Energy

The Habo Energy battery and inverter support backup power. Essential circuit wiring is an optional add-on that your installer can set up during installation.

Even without essential circuit wiring, the core system still saves you £900+ per year on your electricity bill through tariff arbitrage.

Use the savings calculator to see how much you'd save on your daily electricity bill.