Generator Automatic Transfer Switch (ATS): Complete UK Buying Guide (2026)

Unexpected power cuts can disrupt homes, businesses, farms and commercial premises, leaving essential equipment without electricity.

Whether you're protecting your home's heating system, keeping refrigeration running or maintaining business operations during a mains power failure, a reliable backup generator can make a significant difference.

However, having a generator and having an automatic backup power system are two different things.

This is where an Automatic Transfer Switch (ATS) becomes important.

An ATS can detect when mains electricity fails and automatically transfer selected electrical circuits to a compatible generator, without someone having to operate a manual changeover switch.

In this complete UK buying guide, we'll explain how generator automatic transfer switches work, the differences between manual and automatic changeover systems, what equipment you need and which generators are suitable for ATS applications.

We'll also explore the important UK electrical safety considerations and highlight ATS-compatible generators available from Power Generator UK.

What Is a Generator Automatic Transfer Switch?

An Automatic Transfer Switch (ATS) is an electrical switching device used to transfer an electrical load between two power sources, usually the mains electricity supply and a standby generator.

Its purpose is to allow a backup power system to respond automatically when the normal electricity supply is interrupted.

In a correctly designed standby generator installation, the system monitors the mains electricity supply and transfers the connected electrical circuits to generator power when required.

When the normal electricity supply returns and is stable, the system can switch the connected circuits back to mains electricity.

The generator can then enter a controlled cooling-down period before shutting down, depending on the installed control system.

This arrangement provides greater convenience than a manually operated changeover switch, particularly for properties that may be unoccupied when a power cut occurs.

Important: Not every generator supports automatic starting or integration with an ATS. The generator, controller and switching equipment must all be compatible.

How Does an Automatic Transfer Switch Work?

A professionally designed automatic standby power system typically follows a sequence of operations.

1. The ATS Monitors the Mains Supply

While normal mains electricity is available, the connected circuits receive electricity from the utility supply.

The automatic transfer system continuously monitors relevant supply conditions.

2. A Power Failure Is Detected

If the mains electricity supply fails or moves outside the system's permitted limits, the control equipment identifies the interruption.

Depending on the configuration, there may be a short programmed delay before starting the generator.

3. The Generator Starts Automatically

Where the generator supports automatic remote starting and is connected to a compatible controller, the system sends a start command.

The generator starts and begins producing electricity.

4. Power Transfers to the Generator

Once the generator has reached acceptable operating conditions, the ATS transfers the connected electrical load from the mains source to generator power.

The switching system must prevent unsafe simultaneous connection between the generator and the electricity distribution network.

5. The Generator Supplies Electricity

The generator continues powering the selected circuits while the normal electricity supply remains unavailable.

The available backup power depends on the generator's continuous output, the electrical loads and the installation design.

6. Mains Electricity Returns

When the mains supply returns and is sufficiently stable, the system transfers the connected circuits back to the normal supply.

7. The Generator Shuts Down

The generator may continue running briefly without load to complete its programmed cooling-down cycle before shutting down.

The system then returns to standby mode, ready for the next interruption.

An ATS does not normally provide uninterrupted electricity. There is typically a short power interruption while the generator starts and the electrical load transfers.

Equipment that cannot tolerate this interruption may require a suitable uninterruptible power supply (UPS).

What Is the Difference Between ATS and a Manual Changeover Switch?

Both automatic transfer switches and manual changeover switches are used to select between different electricity supplies.

The main difference is how the changeover takes place.

Manual Changeover Switch

A manual changeover switch requires someone to operate the system when mains electricity fails.

Depending on the generator and installation, the operator may need to start the generator separately before switching the selected circuits to generator power.

Manual changeover arrangements are often appropriate where power cuts are infrequent and someone is available to operate the system safely.

Automatic Transfer Switch

An ATS responds to mains power failures automatically when installed as part of a compatible standby system.

With suitable generator starting controls, it can initiate generator operation and manage the changeover without routine manual intervention.

This can be particularly valuable for businesses, rural properties, critical refrigeration systems and premises requiring greater resilience.

ATS vs Manual Changeover: Comparison

Feature	Automatic Transfer Switch	Manual Changeover Switch
Detects mains power loss	Automatically, when configured	Operator identifies outage
Changes supply source	Automatically	Manually
Generator auto-start	Possible with compatible system	Usually started separately
Operator intervention	Generally not required during normal operation	Required
Initial equipment cost	Usually higher	Usually lower
Installation	Professional installation	Professional installation
Suitable for unattended sites	Often advantageous	Limited by operator availability
Continuous, uninterrupted power	No, not by itself	No

Both systems require appropriate isolation, protection and professional installation.

What Are the Benefits of an Automatic Transfer Switch?

1. Automatic Backup During Power Cuts

An ATS-equipped standby generator system can restore electricity to selected circuits automatically when the mains fails.

This is useful during overnight power cuts or where nobody is present to start a generator.

2. Protection for Essential Electrical Equipment

Correctly sized backup systems can help maintain power to equipment such as refrigeration, heating controls, communications systems and security installations.

3. Reduced Business Disruption

For commercial premises, electricity failures can cause interruptions to trading, administration, communications and production.

An automatic backup system can reduce downtime where the connected equipment and generator capacity are suitable.

4. Convenience

There is no need to operate a manual changeover switch during a normal automatic backup sequence.

This makes an ATS particularly attractive for users wanting a more convenient standby power solution.

5. Controlled Return to Mains Power

The system can automatically return to mains electricity when the normal supply has been restored and verified as suitable.

6. Flexible Backup Arrangements

An ATS can form part of a system designed to supply selected essential circuits or a larger proportion of a property's electrical installation.

The appropriate arrangement depends on generator capacity and professional electrical design.

Do All Generators Work With an ATS?

No. Not every generator can be used with an Automatic Transfer Switch.

This is an important consideration when purchasing equipment for emergency backup.

Many conventional portable generators are designed to be started and operated manually.

Even where a generator has an electric starter, this does not automatically mean it supports remote starting or automatic transfer switching.

For example, a generator with a key-operated electric starter may not have the control interface needed to start automatically when mains electricity fails.

For automatic operation, the generator must be compatible with the selected switching and control equipment.

Before purchasing, confirm:

• Whether the generator supports automatic remote starting.

• Whether a compatible ATS connection is available.

• Whether the required controller is built in or supplied separately.

• Whether the selected ATS supports the installation's voltage and electrical configuration.

• Whether the switching equipment has an appropriate current rating.

• Whether the generator has sufficient continuous output for the connected circuits.

• Whether additional accessories or control modules are required.

A generator advertised as ATS-ready does not necessarily include an ATS panel.

It is essential to confirm exactly what is included before placing an order.

Best ATS-Compatible Generators Available from Power Generator UK

At Power Generator UK, we supply a range of petrol and diesel generators that can form part of professionally designed automatic standby power systems.

Below are examples from our current product range.

Compatibility, optional equipment and the final installation arrangement must be confirmed before purchase.

1. Gorilla Power GP6500iE – 6.5kW Petrol Inverter Generator

The Gorilla Power GP6500iE is a petrol inverter generator designed to offer practical portable power and ATS-ready capability.

It offers a maximum rated output of 6.5kW and a continuous rated output of 6.0kW.

Its features include:

• 230V single-phase output.

• Petrol inverter technology.

• Electric starting.

• ATS-ready connection.

• Continuous output of 6.0kW.

• Compact design for its output class.

The GP6500iE may appeal to homeowners and small businesses considering a compatible backup power installation.

As an inverter generator, it is also designed to provide regulated electricity suitable for a wide range of compatible electrical equipment.

Best suited to: Selected domestic backup circuits, workshops, small businesses and applications requiring a compact petrol generator.

View Gorilla Power GP6500iE 6.5kW ATS-Ready Generator

Please note: An automatic transfer switch is not included as standard, and automatic start compatibility must be confirmed for the proposed installation.

2. Gorilla Power GP12800DE – 12.8kW Diesel Generator

For applications requiring greater generating capacity, the Gorilla Power GP12800DE offers a substantial increase in available power.

This heavy-duty diesel generator provides a maximum output of 12.8kW and a continuous output of 12.0kW.

Key features include:

• 12.8kW maximum electrical output.

• 12.0kW continuous output.

• Diesel engine.

• Electric starting.

• ATS-ready connection.

• 35-litre fuel tank.

• Heavy-duty open-frame construction.

• 240V and 120V output connections.

The GP12800DE is suitable for consideration where larger electrical loads need to be supported during power failures.

It may be particularly useful for workshops, farms, commercial properties and appropriately designed domestic backup installations.

Best suited to: Larger backup power requirements and commercial or agricultural applications.

View Gorilla Power GP12800DE 12.8kW Diesel Generator

The correct ATS arrangement, starting controls and electrical connections must be confirmed with a qualified installer before ordering.

3. Excel Power XL-DK-11S – Silent Single-Phase Diesel Generator

The Excel Power XL-DK-11S is a professional 1500RPM silent diesel generator designed for demanding power requirements.

Unlike smaller portable generators, this model is particularly suited to professionally installed applications.

Its main features include:

• 230V single-phase output.

• 1500RPM diesel engine.

• Acoustic weather-resistant enclosure.

• Automatic voltage regulation.

• Digital generator control equipment.

• Optional ATS arrangements.

• Professional fixed-installation suitability.

The generator can be configured with additional equipment, including a compatible Automatic Transfer Switch, subject to the installation requirements.

Its single-phase design makes it a potential option for UK properties and businesses that do not have a three-phase electricity supply.

Best suited to: Home standby power, workshops, commercial premises and agricultural properties.

View Excel Power XL-DK-11S Silent Diesel Generator

4. Excel Power XL-DK-22S – 22kW Silent Diesel Generator

For larger residential and commercial installations, the Excel Power XL-DK-22S offers greater backup power capacity.

This single-phase diesel generator delivers 20kW prime power and 22kW standby power, according to its product specification.

Key features include:

• 230V single-phase output.

• 1500RPM diesel operation.

• Acoustic canopy.

• Digital generator monitoring.

• Automatic voltage regulation.

• Electric starting.

• Optional ATS compatibility.

• 43-litre integrated fuel tank.

When combined with a compatible ATS, the generator can form part of a professionally installed automatic standby power system.

Best suited to: Larger properties, commercial buildings, farms and businesses requiring substantial single-phase backup capacity.

View Excel Power XL-DK-22S 22kW Silent Diesel Generator

5. Excel Power XL-DK-35S – 35kW Silent Diesel Generator

Businesses and larger properties requiring more substantial generating capacity may consider the Excel Power XL-DK-35S.

This heavy-duty 1500RPM diesel generator provides 32kW prime power and 35kW standby power.

Its features include:

• 230V single-phase output.

• 1500RPM water-cooled diesel engine.

• Sound-attenuated canopy.

• Digital control panel.

• Automatic voltage regulation.

• Integrated fuel tank.

• Coolant heating and battery charging equipment.

• Optional ATS-compatible arrangements.

The XL-DK-35S is designed for professionally installed applications where substantial electrical loads need to be supported.

Best suited to: Large residential properties, agricultural installations, commercial premises and demanding standby applications.

View Excel Power XL-DK-35S 35kW Silent Diesel Generator

Explore More Backup Generators

Not sure which generator is suitable for your installation?

Explore our wider product categories:

• Diesel Generators

• Petrol Generators

• Inverter Generators

• Silent Generators

Our team can help you compare generator specifications and discuss available ATS-compatible options.

How Much Does a Generator ATS Cost in the UK?

The total cost of an automatic transfer switch installation depends on several factors.

The ATS equipment itself is only one part of a complete standby power system.

Costs can vary according to:

• The generator's electrical output and voltage.

• The ATS current rating.

• Single-phase or three-phase requirements.

• The type of automatic starting controller.

• The number of electrical circuits requiring backup.

• Electrical protection and earthing requirements.

• Cable lengths and installation complexity.

• Any required distribution board modifications.

• Commissioning and testing.

Smaller domestic systems may require a relatively straightforward changeover arrangement, while larger commercial installations can involve substantial electrical distribution and control equipment.

An ATS should always be selected according to the requirements of the installation rather than simply choosing the cheapest available panel.

Our advice: Obtain an installation assessment and quotation from a qualified electrician or generator installer before purchasing the equipment.

This helps ensure that the generator, ATS and property electrical system will work together correctly.

Can an ATS Power Your Entire House?

An automatic transfer switch can be incorporated into a system designed to support an entire property's electrical installation, but this does not mean every generator is large enough to power every appliance simultaneously.

The generator must have sufficient capacity for the anticipated loads, including motor starting currents and periods of simultaneous use.

For example, a property may require electricity for:

• Refrigerators and freezers.

• Central heating pumps and controls.

• Lighting.

• Broadband and communications equipment.

• Security systems.

• Water pumps.

• Kitchen appliances.

• Electric heating.

• Other essential household equipment.

Some appliances, such as electric showers, large heating systems and electric vehicle chargers, can demand considerable electrical power.

A smaller generator may therefore be better suited to supplying selected essential circuits instead of the entire property.

A qualified electrician can help identify the appropriate backup loads and design the necessary electrical distribution arrangement.

Remember: A generator's maximum output is not the same as its rated continuous operating output.

How Big Should an ATS Generator Be?

Choosing the correct generator size is essential for a successful standby installation.

The generator must be capable of supplying the planned electrical demand without exceeding its operating limits.

When assessing generator capacity, consider:

Continuous Electrical Load

Determine the combined running power required by the appliances and circuits that need backup.

Starting Loads

Equipment containing motors, such as pumps, compressors and refrigeration systems, may require considerably more power when starting.

Simultaneous Use

Consider which electrical appliances may operate at the same time.

Future Requirements

Allow for reasonable future changes to your electrical requirements where appropriate.

Single-Phase or Three-Phase Supply

Your property's electrical configuration will influence which generator and ATS system is suitable.

For commercial installations, generator sizing may also require assessment of power factor, phase balance and load characteristics.

For more information, read our existing Knowledge Centre guide: What Size Generator Do I Need?

You can also contact our team for advice on generator specifications.

Single-Phase vs Three-Phase Automatic Transfer Switches

The correct ATS must be compatible with the electrical installation it is intended to serve.

Single-Phase ATS

Single-phase systems are commonly used in domestic properties and smaller commercial premises with suitable 230V electrical installations.

They are frequently considered for backup lighting, heating equipment, refrigeration and selected household circuits.

Three-Phase ATS

Three-phase systems are generally used in installations requiring a 400V three-phase supply.

These may include factories, workshops, industrial premises and businesses operating larger electrical machinery.

A three-phase system requires the correct equipment and protection arrangements for all relevant phases and connected loads.

Important: Never assume that a single-phase generator is a suitable substitute for a three-phase installation.

The correct generator and transfer switching arrangement must be determined by a qualified professional.

Explore Our Diesel Generator Range

Does an Automatic Transfer Switch Provide Instant Power?

Not usually.

A conventional standby generator takes time to detect the outage, start, stabilise and transfer electrical loads.

The exact delay varies according to the generator and control system.

During this period, connected equipment will generally experience a brief interruption in electricity.

For many homes and workplaces, this interruption may be acceptable.

However, some equipment requires a continuous supply.

Examples include:

• Computer servers.

• Certain medical systems.

• Sensitive telecommunications equipment.

• Specialist industrial controls.

• Critical electronic systems.

These installations may require a suitably specified Uninterruptible Power Supply (UPS) in addition to the generator and ATS.

A UPS can provide electricity during the changeover period, subject to its own capacity and design.

For critical applications, the complete backup arrangement should be designed by an appropriately qualified specialist.

Can You Install a Generator ATS Yourself?

Connecting a generator to a building's electrical installation is not a DIY job.

An ATS must be incorporated into an appropriately designed electrical system with the correct isolation, protection and earthing arrangements.

Incorrect installation can create serious dangers, including:

• Electric shock.

• Electrical fire.

• Damage to connected equipment.

• Unsafe generator operation.

• Backfeeding into the public electricity network.

• Danger to electricity network workers.

• Failure of electrical protective devices to operate correctly.

In the UK, the installation should be designed, installed, inspected and tested by a suitably qualified and competent electrician or generator installation specialist.

The installation must comply with applicable electrical safety requirements, including relevant provisions of BS 7671.

The Electricity Safety, Quality and Continuity Regulations also include requirements intended to prevent switched alternative energy sources from operating in parallel with the distributor's network.

Any network operator requirements should be considered by the installer.

Never attempt to connect a generator to a building by feeding electricity through an ordinary wall socket.

A correctly designed changeover system is required to prevent dangerous connections between the mains supply and generator.

Where Should an ATS-Compatible Generator Be Installed?

Generator location is an important part of any standby power project.

Petrol and diesel generators produce exhaust gases containing carbon monoxide, which can be fatal.

Portable combustion-engine generators must be operated outdoors, away from doors, windows and ventilation openings.

UK public health guidance recommends placing portable generators at least 6 metres from buildings, with the exhaust directed away from openings.

Never run a portable generator inside a home, garage, shed, basement or other enclosed or partially enclosed space.

Fixed standby generators require appropriately designed installation locations, exhaust arrangements, ventilation, clearances and maintenance access in accordance with manufacturer instructions and applicable requirements.

Additional considerations include:

• Generator noise.

• Weather protection.

• Fuel storage.

• Safe refuelling arrangements.

• Accessibility for maintenance.

• Electrical cable routing.

• Fire safety.

• Security and unauthorised access.

Professional advice should be obtained before selecting the final location.

For more information, refer to guidance from the Health and Safety Executive.

Is an ATS Worth It for Home Backup?

An automatic transfer switch can be a worthwhile investment for homeowners who want their backup generator to operate without manual intervention.

It may be particularly useful for:

• Rural homes affected by recurring power cuts.

• Properties with essential electrically powered heating systems.

• Homes with electric water pumps.

• Properties requiring refrigeration protection.

• Households with security systems.

• Second homes or properties that may be unoccupied.

• Larger homes requiring a professionally designed standby installation.

However, an ATS is not necessary for every generator owner.

If you only require occasional portable electricity for a few appliances, a conventional generator used with properly rated connections may be sufficient.

Where selected building circuits require backup, a professionally installed manual changeover system may also provide a lower-cost alternative.

The decision depends on how frequently power cuts occur, how important uninterrupted operations are and the amount you wish to invest.

Is an ATS Worth It for Business Backup?

For many commercial premises, an automatic transfer switch can provide important operational benefits.

Unexpected electricity interruptions can cause disruption to equipment, communications, stock storage and business activities.

An automatic standby power system may help businesses reduce downtime and maintain selected essential operations.

Examples include:

Agriculture: Supporting suitable water pumps, refrigeration, ventilation controls and other essential electrical equipment.

Retail: Providing backup for selected lighting, refrigeration, communications and security systems.

Offices: Supporting networking equipment, communications and critical services.

Warehousing: Maintaining appropriate refrigeration, security and operational systems.

Industrial Premises: Supplying selected machinery, controls or essential infrastructure where generator capacity and installation design permit.

The correct generator size, ATS configuration and any additional UPS requirements should be assessed against the business's actual operating needs.

How Do You Maintain an ATS Generator System?

An automatic standby generator system should be maintained and tested according to the manufacturer's instructions and the requirements of the installation.

Recommended checks may include:

• Generator engine oil and coolant levels.

• Fuel condition and availability.

• Starter battery condition.

• Battery charger operation.

• Controller warnings and fault records.

• ATS condition and operation.

• Electrical connections and protective devices.

• Appropriate functional testing.

• Periodic generator servicing.

• Inspection and testing by competent personnel.

Some professionally installed standby generators feature automatic exercise functions that periodically run the engine.

However, an automatic exercise cycle does not necessarily prove that the entire transfer switching arrangement is functioning correctly.

Appropriate periodic testing and maintenance remain important.

For further advice, see our existing Generator Servicing Basics article in the Knowledge Centre.

Frequently Asked Questions About Generator Automatic Transfer Switches

What does ATS mean on a generator?

ATS stands for Automatic Transfer Switch. It is used to transfer electrical loads automatically between the mains electricity supply and a compatible backup generator.

Can any generator be connected to an ATS?

No. The generator must be compatible with the intended ATS and control arrangement. An electric starter alone does not guarantee automatic starting compatibility.

Does an ATS start the generator automatically?

It can, when the generator supports automatic remote starting and the ATS or associated control equipment is correctly configured.

Can I add an ATS to an existing generator?

Possibly. Compatibility depends on the generator's controls, starting system and electrical specifications. A qualified installer should assess the proposed arrangement.

Is an ATS better than a manual changeover switch?

An ATS offers automatic operation, making it convenient for unattended premises or frequent outages. A manual changeover system can be a more economical option where automatic operation is unnecessary.

Do I need an electrician to install a generator ATS?

Yes. Connections to a building's electrical system should be designed and installed by an appropriately qualified and competent electrician or generator specialist.

Will an ATS stop my appliances from switching off?

Not necessarily. A conventional ATS system normally involves a temporary interruption while the generator starts and the load transfers. Sensitive equipment may require an appropriately specified UPS.

Can I use an ATS with a petrol generator?

Yes, provided the petrol generator supports the necessary control and starting functions and is compatible with the chosen system.

Can I use an ATS with a diesel generator?

Yes. Many professionally installed diesel generators are suitable for automatic standby applications when paired with compatible transfer switching equipment.

Is an ATS included with an ATS-ready generator?

Not necessarily. ATS-ready typically indicates a form of compatibility, not that the switching equipment is included. Always check the product specification and supplied accessories.

Does an ATS work with solar panels or battery storage?

Some advanced backup systems can integrate generators, solar inverters and battery storage. However, compatibility is system-specific and requires suitable controls, protection and professional design.

What happens when mains electricity returns?

A properly configured ATS system can transfer the connected load back to mains power. The generator may then complete a cooling-down period before shutting down.

Conclusion: Is an Automatic Transfer Switch Right for You?

An Automatic Transfer Switch can transform a compatible backup generator into a more convenient standby power system.

Instead of manually starting the generator and changing the electrical supply during a power cut, a correctly designed ATS installation can manage the process automatically.

For homeowners, this can provide greater reassurance when electricity failures occur.

For businesses, farms and commercial premises, automatic backup power may help protect essential operations and reduce disruption.

However, choosing the right equipment is essential.

The generator must support the intended automatic starting functions, the ATS must be compatible with the electrical installation, and all work must be completed by appropriately qualified professionals.

At Power Generator UK, we supply a wide selection of professional petrol, diesel and inverter generators, including ATS-ready models and larger standby generators with optional automatic changeover arrangements.

Find the Right ATS-Compatible Generator

Explore our range:

• Gorilla Power Generators

• Diesel Generators

• Petrol Generators

• Inverter Generators

• Silent Generators

Need Advice on Generator ATS Compatibility?

Our team can help you compare generator specifications, available ATS options and suitable models for your backup power requirements.

Before purchasing, we recommend discussing your proposed electrical installation with a suitably qualified electrician or generator installer.

Call us: 0800 222 9069

Visit: www.power-generator.uk

Power Generator UK — Dependable Power, Wherever You Need It.