What is an automated external defibrillator (AED)?

An Automated External Defibrillator (AED) is a portable life saving device that can give a casualty’s heart an electric shock, when it has stopped beating normally in a sudden cardiac arrest.

A defibrillator works by checking the casualty's heart rhythm once the defibrillator pads are placed on their chest and giving them a shock if needed.

Defibrillators can be used on adults or children over one year old.

By using a defibrillator before an ambulance arrives, you can significantly increase someone’s chance of survival.

When should you use a defibrillator?

Defibrillators are used to treat someone in cardiac arrest. A cardiac arrest is when someone’s heart has stopped beating normally and they are unresponsive and not breathing.

Why is using a defibrillator important?

How much is a defibrillator?

How much does a defibrillator cost?

The cost of a defibrillator can vary depending on the model and its features. Typically, defibrillators can cost between £800 and £2,500.

All defibrillators we sell:

  • come with voice instructions to guide the rescuer through each step of the rescue
  • provide a shock to the patient either automatically or at the press of a button
  • perform daily, weekly and monthly self-tests to let you know if the device is ready for use.

Defibrillators come with varying degrees of protection from dust and water, making some more suitable in harsher environments than others. Some defibrillators will come with additional features, such as an LCD display screen for visual instructions, real time CPR feedback to let the rescuer know the quality and effectiveness of their CPR, or ECG display for more professional models.

To help you decide which defibrillator would best be suited to your workplace, home or community we have put together a list of things to consider below.

How much does a defibrillator cost to maintain?

How much does defibrillator training cost?

When purchasing a defibrillator, think about:

  • who will likely need the defibrillator – in some cases children will need separate paediatric defibrillation pads
  • storing your defibrillator – fixed-location defibrillators should be stored in a cabinet or wall bracket, with appropriate signage
  • training – while you do not need to be trained to use a defibrillator, taking training can ensure you are familiar with the device and ready to act quickly in an emergency. Vitally, rescuers will still need to perform CPR, so it is important to know how to do this
  • educating your community – ensure your colleagues or community members are aware of the defibrillator, its location, how to access it, and how to use it.

Find defibrillators suitable for:


Transport and transportation hubs

Shopping centres and public areas

Harsh environments (sea vessels, industrial sites)


Should a defibrillator be kept in a locked cabinet?

Different ambulance trusts recommend different things when it comes to locking the cabinet. Please check with the ambulance trust in your local area for their advice.

Some defibrillator cabinets are alarmed rather than locked, letting people know that the defibrillator is being accessed.

St John Ambulance believes defibrillators should made as accessible as possible to ensure they can be accessed quickly in an emergency.

Shop defibrillator cabinets and wall brackets

What else to keep with a defibrillator

You will also need:

  • A towel, tissues, or wipes to dry the casualty’s chest if it is wet or sweaty.
  • A razor to shave the casualty’s chest.
  • Scissors to cut away the casualty’s clothing.
  • A face shield for administering CPR.

Shop extra things to keep with a defibrillator

Did you find this information helpful?

Browse defibrillators and accessories


Explore our range of fully and semi-automatic defibrillators and everything you need to help you install and maintain your device.

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Free resources

Download our free defibrillator maintenance posters.

Defibrillator Maintenance Checklist (pdf)

Defibrillator checklist poster

Keep track of pad and battery expiration dates so you know when to reorder replacements before they expire.

Defibrillator Location Poster

Defibrillator location poster

Print as many as you need, write on the location of your defibrillator, then display around your workplace.

Related advice

Defibrillators - a guide for rescuers

Read our guide to understand what a defibrillator is, when you should use a defibrillator, and who can use a defibrillator.

Guide to defibrillator maintenance and upkeep

If you are responsible for the upkeep of a defibrillator in your workplace or community, read our guide for answers to frequently asked questions.

How to use a defibrillator

By using a defibrillator before an ambulance arrives, you can significantly increase someone’s chance of survival. Learn what to do.