Key Takeaways
- Electricity is cheaper overnight and more expensive in the early evening.
- A battery stores cheaper electricity and avoids peak pricing.
- Smart meters (installed in 67% of GB homes) enable ToU tariffs.
- Homes that use more energy at peak times see the greatest benefit.
- Solar + battery + ToU creates a stable, flexible, and balanced energy setup.
Time-of-use tariffs change the price of electricity depending on the hour. Power is cheaper overnight and more expensive in the early evening.
A home battery lets you charge when electricity costs less and use that stored energy during peak times.
With 67% of homes in Great Britain now using smart or advanced meters , most households already have the equipment needed to access flexible tariffs.
In simple terms: a battery helps shift your home’s energy use into the cheaper parts of the day, and that can make a real difference to everyday bills.
What Is a Time-of-Use Tariff?
A time-of-use (ToU) tariff charges different prices depending on when you use electricity. It usually follows a predictable pattern:
- Off-peak: lower-cost hours, often overnight
- Peak: higher-cost hours, often early evening
- Shoulder: the steady, in-between rate
According to Smart Energy GB, ToU tariffs offer lower prices at quieter times and higher prices during busy periods to encourage households to shift usage into cheaper windows .
To use these tariffs, you need a smart meter, and most UK homes already have one installed .
How Arbitrage Works
“Arbitrage” sounds technical, but the idea is very simple:
- Charge your battery at cheaper times.
- Use that stored energy when electricity is expensive.
E.ON Next explains that using off-peak electricity or stored energy instead of expensive peak-time grid power can reduce household import costs when used effectively with a ToU tariff .
A battery makes this automatic:
- It charges during cheaper nighttime hours
- It supplies the home during expensive evening hours
- It cuts down on peak-rate grid electricity
- It works alongside solar if you already have panels
No complicated controls. Just your home using cheaper electricity at the right time.
Why It Matters More in Winter
Winter is when most households feel the pressure:
- Lights are on earlier
- Heating runs for longer
- Evening demand is higher
- Peak times align with busy family routines
ToU tariffs charge the highest prices exactly when homes use the most power.
A battery softens this impact by covering those peak hours, keeping your home running on stored, cheaper electricity instead of expensive grid power.
Simple Winter Weekday Example
Here’s how a home battery works with a time-of-use tariff on a winter weekday:
| Time | What Powers the Home | Tariff Window | Why This Helps |
| 11pm–6am | Battery charges | Off-peak | Uses the lowest-cost electricity |
| 6am–9am | Battery supply | Off-peak / standard | Supports morning routines affordably |
| 9am–4pm | Solar (if available) | Day rate | Reduces daytime grid imports |
| 4pm–8pm | Battery discharges | Peak | Avoids the most expensive hours |
| 8pm–11pm | Battery/grid mix | Shoulder | Smooths into evening use |
This is the core benefit: you cover your most expensive hours without paying peak prices.
How Solar, a Battery, and ToU Tariffs Work Together
Here’s the real-world flow:
- Daytime: solar runs the home
- Excess solar: charges the battery
- Overnight: battery can also charge at cheaper off-peak rates
- Evening: stored energy avoids expensive peak tariffs
It’s not about squeezing every penny. It’s about stable, predictable bills and relying less on high-cost grid electricity, especially in winter.
How to Size a Battery for Time-of-Use Tariffs
A simple approach is to size your battery around your typical evening use, because evenings are often the most expensive hours.
| Evening Use (kWh) | Suggested Battery Size |
| 3–4 kWh | 5 kWh |
| 5–7 kWh | 7–8 kWh |
| 8–10 kWh | 10–12 kWh |
If your supplier’s peak window is long, for example, 4pm–9pm, a slightly larger battery can help cover the full period without dipping into grid power.
Risks and Limits
Not every home gets the same savings.
Here are the points to consider:
- Your routine matters: if you use little energy in the evening, benefits are smaller.
- Tariffs differ: each supplier sets different peak and off-peak windows.
- Smart meter required: while most homes have one, some don’t.
- Battery size matters: too small → you still buy peak power; too big → slower payback.
- Solar export changes: you might export less, but usually save more by using your energy internally.
How Synergy PV Renewables Helps You Choose
Choosing a time-of-use tariff and battery setup only works if it matches the way your home actually runs.
That’s why Synergy looks at the practical details first.
During a consultation, we assess:
- Your smart meter status
- Your current electricity tariff
- Your evening and winter usage patterns
- Whether you have solar today or plan to add it
- Your home’s electrical layout and battery placement options
- Any future plans (EV charging, heat pump, home working)
If a battery won’t deliver meaningful value with your tariff or usage, we explain why and suggest alternatives.
If it will help, we design the right system and handle everything from DNO approval to installation and aftercare.
Our focus is on:
- neat, safe, future-ready installation
- systems that integrate smoothly with your existing electrics
- easy daily operation
- long-term reliability and support
The goal is simple: a system that works well, cuts costs, and fits your home without hassle.
Wrapping Up
Time-of-use tariffs reward you for using electricity at the right time.
A battery makes that shift effortless by charging when energy is cheaper and powering your home during expensive evening hours.
With most UK homes already equipped with smart meters, this is a practical and accessible way to keep bills under control.
Whether or not you have solar, pairing a battery with a flexible tariff can give your home more stability and make your energy costs far easier to manage year-round.
Frequently Asked Questions
- Do I need solar for a ToU tariff to be useful?
A battery alone can take advantage of cheaper overnight rates. - Will a battery always save money on a ToU tariff?
It depends on your evening usage and the tariff structure. - Do I need a smart meter?
Yes, and most homes already have one installed in smart or advanced mode. - Do ToU tariffs change seasonally?
Some suppliers adjust winter peak windows, so it’s worth checking the details. - Is the setup complicated to use?
The battery controls the charging and discharging automatically.
