How Night-Time Tariffs and Solar Batteries Can Work Together

As energy prices continue to fluctuate across the UK, homeowners are becoming increasingly savvy about how and when they use electricity. One strategy gaining attention is combining solar batteries with night-time or off-peak tariffs. This pairing allows households not only to store their own solar energy but also to buy cheap grid electricity overnight – then use it during the day when prices are higher.

Here’s how it works, why it matters, and what to watch out for.

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🌙 What Are Night-Time Tariffs?

Night-time tariffs, also known as off-peak or time-of-use tariffs, offer cheaper electricity rates during certain low-demand hours – usually overnight.

Common UK examples include:

• Octopus Go / Go Faster
• EDF GoElectric
• OVO Charge Anytime
• Economy 7 and Economy 10 (traditional dual-rate tariffs)

During off-peak hours (often between midnight and 4–5 am), electricity can cost a fraction of the daytime rate. Traditionally, this helped EV drivers and households with storage heaters – but it now benefits solar battery owners too.

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⚡️How Night-Time Tariffs Fit into a Solar PV System

A modern UK solar setup typically includes:

1. Solar panels (PV array) – generating DC electricity during daylight.
2. An inverter – converting DC to AC power for home use.
3. A solar battery – storing excess solar energy for later use.
4. A smart meter or home energy management system – monitoring and controlling imports, exports, and tariffs.

When you introduce a night-time tariff, you simply give your battery a second charging option – from the grid, not just from your panels. The system intelligently decides when to charge and discharge, based on the time of day and tariff rate.

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☀️ Daytime – Solar Comes First

During daylight:

• Your solar panels power your home directly.
• Any excess generation charges your solar battery.
• Once full, any leftover energy can be exported to the grid, possibly earning you payments via the Smart Export Guarantee (SEG).

👉 This is your system’s “free” charging mode – no grid electricity used.

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🌙 Night-Time – Off-Peak Tariff Kicks In

When the sun sets, most systems automatically switch to battery power.

With a night-time tariff, you can also top up your battery using cheap grid electricity.

During the off-peak window (for example, midnight to 4am):

• The inverter or smart controller detects the low-rate period.
• The battery charges using off-peak electricity.
• In the morning, that stored energy powers your home – avoiding expensive daytime imports.

Essentially, your battery acts as a time-shift tool, storing low-cost energy for peak hours.

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⚙️ Smart Control and Automation

Modern solar battery systems (Tesla Powerwall, GivEnergy, SolarEdge, etc.) can:

• Prioritise solar charging first (to maximise self-consumption).
• Automatically charge from the grid during the cheapest tariff window.
• Optimise discharge to avoid exporting power at low prices.

All of this is managed through the manufacturer’s smart app or inverter software, meaning you don’t need to manually adjust anything.

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🕰️ Seasonal Balance

In summer, solar panels generate plenty of electricity, so your battery will usually fill from solar alone.

In winter, when days are short and generation drops, the battery can charge from the grid overnight – giving you a reliable, low-cost energy supply all year round.

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🔋 Example Setup

Let’s imagine:

• 4 kW solar PV system
• 9.5 kWh battery
• 7.5p/kWh off-peak, 30p/kWh peak

In summer:

• Solar fills the battery by mid-morning.
• Battery powers your home through the evening – no need for grid charging.

In winter:

• Solar only half-fills the battery.
• System automatically tops it up at 2am using off-peak electricity.
• You wake up with a full battery ready for the expensive daytime period.

Result: lower bills and better use of your solar system all year round.

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🔧 How Power Flows – Simple Overview

Time of Day	Power Source	What Happens
Daytime	Solar panels	Powers home + charges battery
Evening	Battery	Powers home from stored solar
Night (off-peak)	Grid	Optional cheap battery top-up
Morning	Battery	Powers home with stored energy

Your battery works like an energy “buffer”, always drawing from the cheapest or greenest source available.

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💡 Things to Consider

• Efficiency: Expect around 90–95% round-trip solar battery efficiency (a small loss in conversion).
• Battery size: Larger batteries make better use of night tariffs.
• Smart meter: Required for time-of-use tariffs.
• Installer approval: Your system must comply with G98/G99 regulations for grid charging and export.

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🌍 Environmental Benefits

Charging at night often coincides with high wind generation in the UK, meaning your electricity is cleaner as well as cheaper.

This reduces strain on the grid and supports renewable balancing – a win for both your wallet and the planet.

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Key Takeaway

Combining a solar battery with a night-time tariff lets UK residents:

✅ Cut daytime electricity costs

✅ Use cleaner energy during off-peak hours

✅ Maximise solar self-consumption

✅ Stay energy-resilient year-round

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In Summary

The future of British home energy lies in smart storage and flexible pricing. As more energy providers introduce dynamic tariffs, homes that can store power – whether from the sun or the grid – will be best placed to save money and reduce emissions.

If you already have a solar battery, check whether it can automatically charge during your off-peak tariff window. It’s a small setting that could make a major difference to your energy bills and your carbon footprint.