Winter Generator Storage Guide: How to Store Your Generator Safely

Winter can be hard on generators, particularly if they are left unused for long periods in cold, damp or poorly ventilated conditions.

Whether you own a petrol generator, diesel generator, inverter generator or larger commercial unit, correct winter storage can help prevent starting problems, fuel issues, corrosion, battery failure and unnecessary engine damage.

A few simple maintenance steps before storage can make a major difference when you come to use the generator again.

In this guide, we explain how to prepare a generator for winter, how to store petrol and diesel models correctly, what to do with batteries and fuel, and how to keep your generator ready for reliable use.

You can also explore our full range of Petrol Generators, Diesel Generators and Inverter Generators.

Why Is Winter Generator Storage Important?

Generators contain engines, electrical systems, fuel components, batteries and metal parts that can all be affected by cold and damp conditions.

Poor winter storage may contribute to:

• Difficult starting

• Flat batteries

• Stale fuel

• Carburettor blockages

• Fuel contamination

• Rust and corrosion

• Damaged electrical connections

• Cracked hoses

• Reduced engine reliability

• Moisture inside the generator

If your generator is only used occasionally, preparing it properly before winter storage is especially important.

A generator stored correctly is much more likely to start and operate normally when it is needed again.

Read the Manufacturer's Storage Instructions

Before storing any generator, check the manufacturer's manual.

Different engines and fuel systems may have different storage requirements.

The manual may provide specific guidance on:

• Fuel draining

• Fuel stabilisers

• Engine oil

• Battery storage

• Long-term storage

• Ventilation

• Cleaning

• Generator positioning

• Restarting after storage

Always follow the instructions for your exact model.

General advice can be useful, but the manufacturer's recommendations should take priority.

Clean the Generator Before Storage

A generator should be clean before it is stored.

Mud, dust, oil and debris can trap moisture against metal surfaces and make corrosion more likely.

Generators used on construction sites, farms and workshops may collect significant levels of dust and dirt during normal operation.

Before winter storage:

• Remove loose dirt and debris

• Clean cooling vents

• Wipe the frame

• Check control panels

• Clean around the fuel cap

• Inspect wheels and handles

• Check the engine area

Do not spray water directly into electrical components, the engine air intake or control panel.

Allow the generator to dry fully before storage.

Our Open Frame Generators are designed for demanding trade and construction use, but they still benefit from careful cleaning before long-term storage.

Inspect the Generator for Damage

Winter storage is a good opportunity to carry out a general inspection.

Look for:

• Fuel leaks

• Oil leaks

• Damaged cables

• Loose sockets

• Broken switches

• Loose bolts

• Cracked hoses

• Damaged wheels

• Corrosion

• Exhaust damage

Repairing problems before storage means the generator is more likely to be ready when needed again.

Do not store a machine with a known fuel leak or electrical fault.

Change the Engine Oil if Required

Engine oil can contain contaminants after extended use.

If the generator is due an oil change, completing it before long-term storage can be a good idea.

Fresh oil helps leave the internal engine components protected during the storage period.

Check the manufacturer's service schedule before deciding when to change the oil.

Use only the recommended grade and quantity.

If the generator is not due an oil change, at minimum check that the level is correct before storage.

Do not overfill the engine.

Petrol Generator Winter Storage

Petrol generators require particular attention because petrol can deteriorate during storage.

If old fuel is left inside a generator for months, it can create deposits within the carburettor and fuel system.

This may cause problems such as:

• Generator cranks but will not start

• Generator starts and stops

• Rough running

• Surging

• Blocked carburettor jets

If you own a Petrol Generator, follow the manufacturer's fuel-storage instructions carefully.

Some manufacturers recommend draining the fuel system before long-term storage.

Others may permit the use of an approved fuel stabiliser.

Do not assume one approach is suitable for every generator.

Should You Drain Petrol Before Winter?

Whether petrol should be drained depends on the generator and the length of storage.

For extended storage, many users choose to remove old petrol so it cannot degrade inside the fuel system.

A typical process may involve draining the fuel tank and carburettor, but the exact procedure varies.

Always follow the manufacturer’s instructions and carry out fuel handling outdoors away from flames, sparks or ignition sources.

Use an approved container for any fuel removed from the generator.

Never pour unwanted petrol onto the ground or into drains.

What Is a Fuel Stabiliser?

Fuel stabilisers are products designed to slow the deterioration of petrol during storage.

If a manufacturer approves their use, they may help maintain fuel quality for a longer period.

However, adding stabiliser does not make petrol last indefinitely.

If using one:

• Choose a product suitable for the fuel

• Follow the dosage instructions

• Add it to fresh petrol

• Run the generator if instructed so treated fuel reaches the fuel system

Always check whether the generator manufacturer recommends this approach.

Diesel Generator Winter Storage

Diesel generators have different storage considerations.

Diesel fuel does not behave in exactly the same way as petrol, but it can still become contaminated over time.

Potential problems include:

• Water contamination

• Sediment

• Blocked fuel filters

• Microbial growth

• Cold-weather fuel issues

For larger commercial or standby applications, fuel quality should be monitored carefully.

If a diesel generator is being stored for an extended period, follow the engine manufacturer's requirements regarding fuel treatment, tank level and filters.

Browse our Diesel Generators for models suitable for commercial, standby and long-running applications.

Diesel Fuel and Cold Weather

Low temperatures can affect diesel fuel.

In sufficiently cold conditions, wax crystals can form and restrict fuel flow.

This can cause starting and running problems.

Businesses operating generators throughout winter may need to consider:

• Appropriate winter-grade diesel

• Fuel additives approved by the manufacturer

• Fuel tank protection

• Fuel heaters on certain installations

The requirements depend heavily on the location, temperature and generator design.

Do not add fuel treatments unless they are suitable for the engine and fuel system.

Check the Fuel Filter

Before winter storage, inspect the fuel filter if it is part of the scheduled maintenance.

A contaminated filter left in the generator over winter may contribute to starting problems later.

Diesel generators may also use water separators.

Drain or service these according to the manufacturer's instructions.

Replacing filters before or after winter depends on the service schedule, so check the manual.

Protect the Starter Battery

Battery failure is one of the most common reasons an electric-start generator will not start after a long period of storage.

Cold weather can reduce battery performance, while batteries also naturally lose charge over time.

Before winter storage:

• Check the battery terminals

• Remove corrosion if appropriate

• Ensure connections are secure

• Check battery voltage

• Recharge if required

For long-term storage, the manufacturer may recommend disconnecting the battery or using a suitable maintenance charger.

Do not use an inappropriate charger.

Battery chemistry and charging requirements vary.

Battery Maintainers

A quality battery maintainer can help keep a starter battery charged during storage.

Unlike a basic charger that may continuously supply current, a suitable smart maintainer can monitor the battery and adjust charging automatically.

This may be particularly useful for:

• Standby generators

• Electric-start diesel generators

• Commercial equipment

• Generators stored for several months

Always ensure the charger is compatible with the battery type.

Protect the Generator From Moisture

Damp conditions can be extremely damaging to stored machinery.

Moisture encourages corrosion and can affect electrical connections.

The ideal storage location should be:

• Dry

• Secure

• Well ventilated

• Protected from rain

• Protected from standing water

• Away from excessive condensation

Avoid placing the generator directly on damp soil.

A solid, dry surface is preferable.

However, remember that a generator storage space is not automatically a safe operating location.

A petrol or diesel generator must still be moved to a suitable outdoor operating position before use unless it is part of a professionally designed installation.

Should You Cover a Generator in Storage?

A generator cover can protect the machine from dust and dirt.

However, using the wrong cover can trap moisture inside.

If a cover is used for storage, choose one designed for the generator and make sure the machine is completely dry before covering it.

Do not cover a hot generator.

Never operate a portable generator while it is enclosed inside a normal storage cover.

If you are storing a generator in an outbuilding, ensure there is sufficient ventilation around the stored equipment to help prevent condensation.

Store the Generator Somewhere Secure

Generators can be valuable pieces of equipment.

Security should therefore be considered during winter storage.

Where possible:

• Keep the generator in a locked building

• Limit visibility from outside

• Use suitable security measures

• Keep serial numbers recorded

• Maintain purchase records

Businesses with multiple generators may also want to maintain an asset register.

Keep the Generator Off the Ground

Where practical, avoid leaving a generator directly on a damp floor for several months.

Moisture can collect underneath frames and wheel assemblies.

A dry floor or suitable raised surface can reduce prolonged exposure to damp.

Make sure the generator remains stable.

Do not place a heavy generator on an unsuitable shelf or platform.

Inspect the Air Filter

Before storage, inspect the generator's air filter.

A heavily contaminated filter should be cleaned or replaced according to the manufacturer’s instructions.

Leaving a filter packed with dust and debris over winter is unnecessary and may contribute to poor performance when the generator is used again.

Construction and agricultural generators may require particular attention because they often operate in dusty environments.

Check the Spark Plug on Petrol Generators

If the spark plug is due for inspection or replacement, winter storage can be a convenient time to carry out the work.

Check the manufacturer's servicing requirements.

A worn or heavily fouled spark plug can contribute to poor starting when the generator comes back into use.

Always use the correct replacement spark plug.

Do not overtighten it.

Protect Against Rodents

Generators stored in sheds, barns and agricultural buildings may attract rodents.

Mice and rats can damage:

• Wiring

• Insulation

• Air filters

• Hoses

• Plastic components

Before bringing the generator back into service, inspect it for evidence of animal damage.

This is particularly important if the generator has been stored for several months.

Should You Start a Generator During Winter Storage?

Some generators may benefit from periodic test running, particularly if they are maintained as standby equipment.

However, repeatedly starting a generator for only a few minutes can be counterproductive.

A short run may not allow the engine to reach full operating temperature and may encourage condensation.

If periodic testing is recommended, follow the manufacturer's procedure regarding:

• Warm-up

• Operating duration

• Electrical load

• Shutdown

Larger standby generators may have automatic exercise cycles.

Portable generators may have different storage guidance.

Exercise Standby Generators Correctly

A standby generator should never be assumed to work simply because it started months ago.

For businesses relying on emergency power, a regular testing and servicing programme is important.

A commercial generator may need periodic:

• Start testing

• Battery inspection

• Fuel checks

• Load testing

• Control panel testing

• Automatic transfer testing

Professional generator servicing may be appropriate for critical installations.

Winter Storage for Inverter Generators

Inverter Generators are often used for camping, caravans, motorhomes and home backup.

Their engine storage requirements are broadly similar to other petrol generators, including fuel management, oil checks and battery care where fitted.

However, inverter generators also contain sensitive electronic components.

Keep them dry and protected from excessive condensation.

Avoid storing them where moisture can enter through ventilation openings.

Winter Storage for Silent Generators

Silent Generators use acoustic enclosures designed to reduce operating noise.

Before storage:

• Clean air vents

• Inspect door seals

• Check acoustic panels

• Check for water ingress

• Inspect exhaust components

Even though the enclosure offers additional protection, the generator should still be stored in a suitable dry environment where possible.

Winter Storage for Open Frame Generators

Open-frame machines expose more of the engine and alternator to the surrounding environment.

This makes correct dry storage particularly important.

Our Open Frame Generators are suitable for demanding trade, workshop and construction applications, but prolonged storage in damp conditions can still encourage corrosion.

Clean the generator thoroughly and inspect exposed metal components before winter.

Winter Storage for Three-Phase Generators

Larger Three-Phase Generators may form part of a commercial or industrial power system.

Storage and winter preparation should therefore include the electrical installation as well as the engine.

Depending on the generator, checks may include:

• Starter battery

• Fuel

• Coolant

• Alternator

• Control panel

• Circuit breakers

• Automatic transfer equipment

A qualified engineer should inspect electrical systems where required.

Check Coolant on Liquid-Cooled Generators

Larger diesel generators may be liquid cooled.

If the generator could be exposed to freezing temperatures, coolant protection is essential.

The cooling system should contain the correct coolant mixture specified by the manufacturer.

Do not use plain water where freezing is possible.

Incorrect coolant concentration can allow freezing and potentially cause severe engine damage.

If you are uncertain, have the system inspected professionally.

Record the Generator's Condition

Before putting a commercial generator into winter storage, record:

• Engine hours

• Oil change date

• Filter condition

• Fuel level

• Battery voltage

• Known faults

• Next service date

This makes it much easier to recommission the generator later.

Businesses operating several machines may find service records especially useful.

Do Not Forget Extension Leads and Accessories

Generator accessories should also be stored correctly.

Inspect:

• Extension leads

• Plugs

• Adaptors

• Distribution equipment

• Covers

• Connectors

Damaged cables should be removed from service.

Store electrical accessories somewhere dry.

Do not coil wet cables and leave them in storage for several months.

Preparing a Generator for Use After Winter

When winter storage ends, do not simply start the generator and immediately connect a heavy electrical load.

Carry out a basic inspection first.

Check:

• Fuel condition

• Engine oil

• Starter battery

• Air filter

• Wiring

• Fuel lines

• Exhaust

• Cooling vents

• Sockets

• General condition

Look for leaks, corrosion or rodent damage.

If fuel has been stored in the machine for an extended period, make sure it remains suitable for use.

First Start After Storage

Move the generator to a safe outdoor operating location.

Follow the normal manufacturer starting procedure.

Start with electrical loads disconnected unless the manufacturer specifies otherwise.

Allow the engine to stabilise.

Check for:

• Warning lights

• Fuel leaks

• Oil leaks

• Unusual smoke

• Abnormal noise

• Excessive vibration

Only connect equipment once you are satisfied the generator is operating normally.

Test the Generator Before You Need It

Do not wait until an emergency power cut to discover that your generator will not start after winter.

Test it before the period when it is likely to be required.

This is particularly important for:

• Home backup generators

• Business standby generators

• Farm generators

• Construction equipment

• Event equipment

A short inspection and test can reveal a weak battery or fuel problem before it becomes an emergency.

Portable Power Stations and Winter Storage

Portable Power Stations have different storage requirements because they do not contain combustion engines or liquid fuel.

However, their batteries still require care.

Lithium battery performance and lifespan can be affected by extreme temperatures.

Follow the manufacturer's guidance regarding:

• Storage temperature

• Battery charge level

• Recharging intervals

• Moisture protection

Do not assume a battery power station can simply be left completely discharged throughout winter.

Battery-powered alternatives can be particularly convenient for occasional home backup because there is no petrol, carburettor or starter battery to maintain.

Common Winter Storage Mistakes

Avoid these common mistakes:

• Leaving old petrol in the generator without checking manufacturer guidance

• Storing with a flat battery

• Leaving the generator outside uncovered

• Storing on a damp floor

• Ignoring coolant protection

• Leaving the machine dirty

• Forgetting servicing

• Running the generator indoors

• Allowing rodents access

• Ignoring known faults until spring

Preparing the machine properly takes relatively little time compared with repairing storage-related damage.

Generator Winter Storage Checklist

Before storage:

• Read the manufacturer's manual

• Clean the generator

• Inspect for damage

• Check engine oil

• Service if required

• Manage petrol or diesel correctly

• Inspect filters

• Check battery condition

• Inspect coolant where applicable

• Ensure the generator is dry

During storage:

• Keep the generator secure

• Protect it from moisture

• Maintain the battery if appropriate

• Follow any recommended exercise schedule

• Check periodically for leaks or damage

Before returning to service:

• Inspect fuel

• Check oil

• Check battery

• Inspect cables

• Check filters

• Look for corrosion

• Inspect for rodent damage

• Test the generator safely outdoors

Shop Generators for Year-Round Power

If your existing generator has become unreliable or you need additional backup power for winter, explore our generator ranges:

• Petrol Generators

• Diesel Generators

• Inverter Generators

• Silent Generators

• Open Frame Generators

• Three-Phase Generators

• Portable Power Stations

Whether you need portable electricity for trade use, emergency home backup or commercial standby power, correct storage and maintenance can help ensure your equipment is ready when required.

Final Thoughts

Correct winter generator storage is about protecting the engine, fuel system, electrical components and battery during periods of reduced use.

Clean the generator before storing it, deal with fuel according to the manufacturer's instructions, keep the battery maintained and protect the machine from cold, damp and condensation.

Petrol generators require particular attention to fuel storage, while larger diesel generators may also require fuel, coolant and battery checks.

Most importantly, do not leave a generator untouched for months and simply assume it will work when needed.

Good winter preparation, sensible storage and regular maintenance can significantly reduce generator starting problems and help provide reliable power year after year.