Battery Arbitrage: How Battery Storage Can Save Money Without Solar Panels

When most people think about battery storage, they immediately think about solar panels. But you don't necessarily need solar to benefit from a home battery.

With the growth of time-of-use and split electricity tariffs, battery storage can be charged from the grid when electricity is cheap and used when electricity prices are higher.

This is known as battery arbitrage – and for the right property and tariff, it can provide significant savings even without a single solar panel on the roof.

What is battery arbitrage?

Battery arbitrage is relatively simple:

Charge your battery when electricity is cheap → Store the energy → Use it when electricity is expensive.

For example, a household may have a tariff offering overnight electricity at 8p/kWh, while electricity consumed during peak periods costs 35p/kWh.

Instead of purchasing electricity at 35p during the day, the battery can charge overnight and provide that stored electricity when rates are higher.

The greater the difference between the cheap and peak rates, the greater the potential value of each unit of electricity moved from one period to another.

What could battery arbitrage save?

Consider a tariff with:

Peak rate: 35p/kWh Off-peak rate: 8p/kWh

That's a difference of 27p per kWh.

If sufficient energy is used each day to cycle the battery, the simplified potential annual value looks like this:

Battery Storage	Saving per Full Cycle	Illustrative Annual Value*
10 kWh	£2.70	£985/year
20 kWh	£5.40	£1,971/year
30 kWh	£8.10	£2,957/year

Now consider a less extreme tariff difference:

Peak rate: 30p/kWh Off-peak rate: 10p/kWh

That's still a 20p/kWh difference.

Battery Storage	Saving per Full Cycle	Illustrative Annual Value*
10 kWh	£2.00	£730/year
20 kWh	£4.00	£1,460/year
30 kWh	£6.00	£2,190/year

These simple examples demonstrate why battery storage can have financial value even without solar generation.

Figures are illustrative and assume the stated amount of energy can be shifted every day. Actual savings will be lower or higher depending on usable battery capacity, charging and discharging efficiency, household consumption, tariff structure, battery settings and how frequently the available capacity is cycled.

What if I can't have solar panels?

Not every property is ideally suited to solar.

You may have:

• Insufficient roof space

• Significant shading from trees or neighbouring buildings

• An unsuitable roof orientation or structure

• Planning or aesthetic restrictions

• A listed building

• A property where installing enough solar panels simply isn't practical

That doesn't necessarily rule out battery storage.

A standalone battery can be charged directly from the grid during cheaper tariff periods and then used to reduce the amount of expensive electricity purchased during peak periods.

For properties with high electricity consumption but limited solar potential, battery arbitrage can provide an alternative route to reducing energy costs.

Solar and battery arbitrage can work together

Where solar is suitable, the two strategies can complement each other.

During the day, excess solar generation can charge the battery rather than being exported to the grid. At other times – particularly during winter when solar generation is lower – cheap off-peak grid electricity can be used to charge the battery.

A well-configured system can therefore make use of both low-cost grid electricity and renewable solar generation, depending on the season and energy requirements of the property.

Battery storage can also provide backup power

There is another major advantage to installing battery storage: energy security.

Choosing the right battery system can open the door to installing an EPS or backup gateway, allowing stored electricity to be used if the grid goes down.

Systems from manufacturers including Sigenergy, Tesla and Fox ESS can be configured with backup functionality, subject to the equipment selected and electrical design.

For example, Sigenergy offers its Sigen Energy Gateway for backup applications, while Tesla Powerwall can operate with Tesla's backup equipment. Fox ESS also offers EPS and whole-home backup solutions for compatible storage systems.

This means the same battery being used every day to take advantage of cheaper electricity can also maintain a dedicated backup reserve for use during a power cut.

A homeowner might, for example, choose to use part of the battery for everyday energy savings while retaining a minimum state of charge specifically for emergency backup.

EPS vs Backup Gateway – What's the Difference?

Battery storage can provide protection during a power cut, but not every battery installation automatically provides backup power. The type of backup available depends on the inverter, battery and additional equipment installed.

What is an EPS?

An EPS (Emergency Power Supply) is a backup output available on certain battery and inverter systems. During a grid outage, it allows stored battery energy to continue supplying designated essential circuits, such as lighting, internet equipment, refrigeration or selected sockets.

EPS capacity is limited by the power output of the equipment, so the circuits and expected loads need to be considered carefully when designing the system.

What is a Backup Gateway?

A backup gateway takes this a step further. It sits between the property and the electricity grid, automatically detecting an outage and safely isolating the property from the grid. A compatible battery system can then continue supplying the backed-up electrical installation.

Depending on the system and electrical design, this can allow much greater backup coverage – potentially including the whole property – rather than only a small number of dedicated essential circuits.

Systems such as Sigenergy SigenStor and Tesla Powerwall can be paired with dedicated gateway technology to provide this type of automatic backup functionality.

Which one do I need?

The main difference is the scale and method of backup. EPS is commonly used to provide backup to selected essential circuits, while a properly designed backup gateway system can provide significantly broader backup capability.

Neither approach requires solar panels. A battery can be charged from the grid and maintain a minimum emergency reserve ready for a power cut. However, adding solar can provide another layer of resilience by allowing available solar generation to support loads and potentially replenish the battery during an extended outage.

At Eco Energy, we assess the property's electrical supply, battery system, expected loads and required backup duration before recommending the most appropriate solution.

Do I need solar for battery backup?

No.

A battery can be installed without solar, charged from the grid and configured to retain energy for backup where compatible backup equipment is installed.

Adding solar can improve resilience further. During a prolonged outage, a suitably designed solar and battery system may allow available solar generation to support the property and replenish the battery.

Without solar, once the available backup energy has been consumed during an extended outage, the battery will normally need the grid supply to return before it can recharge.

Is a bigger battery always better?

Not necessarily.

Battery capacity should be matched to your electricity consumption, tariff and objectives.

Installing 30 kWh of storage doesn't automatically mean you'll save three times as much as someone with 10 kWh. To achieve the theoretical arbitrage benefit, you need sufficient electricity consumption to make use of the stored energy.

The right question isn't simply:

“How big a battery can I install?”

It's:

“How much electricity can I realistically move from my cheap tariff into my expensive tariff period?”

That's where proper system sizing becomes important.

Battery storage without solar – does it make sense?

For the right property, absolutely.

Solar remains one of the most effective ways of generating your own electricity, but a property that isn't suitable for solar doesn't have to miss out on the benefits of energy storage.

A standalone battery can potentially help you:

• Buy more electricity when it's cheapest

• Reduce peak-rate grid consumption

• Take advantage of time-of-use tariffs

• Reduce exposure to expensive daytime electricity

• Add emergency backup capability

• Prepare the property for solar at a later date

Modern battery storage is therefore about much more than simply storing excess solar energy.

Find the right battery for your property

At Eco Energy, we can assess your electricity consumption, existing tariff and property requirements to determine whether battery arbitrage could work for you.

Whether you're considering battery storage on its own, solar and battery together, or a battery system with backup protection, we'll design the system around how you actually use electricity.

Interested in battery storage without solar? Get in touch with Eco Energy to find out how much you could save.