Automated External Defibrillator (AED) Buyer's Guide

Timely defibrillation is considered the single most important factor in the treatment of Cardiac Arrest in a Pre-Hospital environment.  With the increased public awareness of AED's together with their improved technological advances, ease of use and decreasing prices, the provision of an AED is now considered a reasonable consideration in a First Aid Needs Assessment.

If you feel an AED is appropriate to your needs, there are a range of machines available, with each manufacturer claiming to offer the best machine.   We don't sell AEDs and we have no commercial interest in any manufacturer so the information provided within this article is completely objective.  what is important is you choose the right AED for your particular needs. 

Here are a few considerations to make before purchasing an AED.


Decision Factors

With a larger, more established manufacturer one should have a greater availability of parts and more accessible customer services.  This is not always true in the commercial world but all manufacturers here are of generally equal quality and reputation.


Price is a consideration that every individual or business should make.   Price does not always relate to quality or functionality but most machines currently start at around £1,000 and generally go no higher than £3,000 for pubic access or lay-responder devices.  Every AED analyses rhythm and then, if required, delivers a shock.   There is no need to pay more than £1,500 for basic functionality but increasing price tends to equate to longer warranty, longer battery and pad life, greater durability and build quality and so on.


Semi or Fully Automatic?
One of the big questions is do you purchase a Fully Automatic or Semi Automatic device?  

A Fully Automatic device is best suited to those with little or no training and those operating in relatively quiet environments.  After the device has been turned on and the pads applied it will analyse the heart rhythm and, if required, it will announce "Stand clear - delivering shock!" (or words to that effect) before automatically delivering a shock.   

A Semi Automatic device will prompt the user to deliver the shock, if required, by pressing a button with a command similar to "Shock required - Press the flashing button now!" 

The benefit of a fully automatic device is the speed to defibrillation as it does not require the user to deliver the shock.  

Semi-automatic devices are a safer option in our opinion as there is the chance of the user or a bystander being in contact with the casualty while the shock is automatically delivered if they are not able to hear the audible warning.   The semi automatic device requires the user to make certain that no one is in contact with the casualty before delivering the shock.   With practice and familiarity with the AED there is no reason why a Semi Automatic device should be any slower in delivering the shock when operated by a competent person.


Energy Delivery
AEDs deliver a fixed current (usually or 150J) for every 'shock' or an escalating current from the first and subsequent shocks e.g 200J followed by 300J and 360J.

There is little or no difference in the survival rates of those who are successfully defibrillated on the first shock (150J versus 200J) but there is a slightly increased chance of recovery for those who receive escalating defibrillation from subsequent shocks.(1)


IP Rating
This two-digit value represents the machine's tolerance to dust and moisture.  A rating of 55 would be more resilient to dirty environments.  A device with a rating of 21 would be better suited to a more traditional office environment.

IP Rating.png


CPR Coaching
Some devices have a 'CPR Coaching' facility.   This may be a basic metronome to help regulate the speed of your compressions or it may give verbal feedback on the quality of your compressions including, depth, location and rate.  For the lay rescuer with no First Aid training this would be valuable.  For the experienced responder this is less of a priority.  


ECG monitoring allows the AED to collect information about the casualty's heart rhythm which may be of use for healthcare professionals once the care of the casualty has been handed over post treatment.  This is an additional feature which does not immediately benefit the casualty but may support better care when the casualty is handed over to the next echelon of care.

The collection of data is a requirement of AEDs and can be used to examine the treatment the casualty received.  The amount of memory required should be based on how long one can expect to deal with the casualty before being able to hand over to a healthcare professional.

Data Download
Data collected can be downloaded in a variety of ways, typically via a Data Card, USB cable or sometimes via Infra red connection or Wi-Fi.  


Battery Standby Life
Some batteries can cost up to £400.00   For this price you would expect significant life from them.  Others are significantly cheaper but don't last as long.   For the regular user, the battery will be depleted much sooner.  For the occasional user there is mileage in having a long-life battery as it reduces the regularity of battery replacement.  For regular uses, some models are available with rechargable batteries as an optional extra.   This increases your initial expense but should save money over the longer term.


Electrode Shelf Life
Similarly the electrodes or 'pads' have a shelf life whether they are used  or not.   Short life pads are not necessarily cheaper.   Some pads feature a compression analysis pad on the sternum which provides guidance on the quality of your chest compression - this is an additional cost which is thrown away once the pads expire.   One brand features the battery built into the pad unit; if the device is rarely used this reduces the long term running costs.  If the device is used frequently this can significantly increase costs as the batteries are thrown away after each use.


Annual Costs
In the table below we have calculated the annual costs of ownership (replacing the batteries and pads) by simply dividing the cost of the replacement battery and pads by their respective shelf lives and adding the two values together.  This can give an indication of how expense the device is to own.  These costs are based on replacing the batteries and pads at the time of shelf life expiration.   If the device is used more often the annual costs will increase.


Number Crunching

In this table we have compiled a list of the most commonly available AEDs in the UK for comparison.

To view the table in full screen, click here.


Which is best?

Lets apply an iterative process here; firstly let's get rid of the Fully Automatic defibrillators.   That still leaves an awful lot.   So now lets get rid of the Fixed energy delivering AEDs.   That gets rid of every device from CU Medical Systems, Defibtech, Philips and Schiller.

Now we are getting closer.   Lets get rid of everything which has a warranty of less than 5 years and a battery life of 5 years and a pad life of less than 3 years.  You want something which is going to last.

Now we've got a smaller range and all seem to be in the similar budget so let's get rid of everything which has an annual running cost of over £46.00 per year.

We've still got a selection.

So now lets get rid of everything which weighs over 2kg.  You don't need extra weight.

That leaves us with the Heartsine Samaritan PAD 350 and 500.  The difference between the two is the 500 features CPR coaching where the 350 does not...but it costs £465.00 more.  The decision of whether you chose a 350 for lower cost or 500 for the CPR coaching is entirely up to you.

Heartsine Samaritan PAD 350

Heartsine Samaritan PAD 350

Heartsine Samaritan PAD 500

Heartsine Samaritan PAD 500


Does this mean these are the best AEDs on the market?

No.   But they are clearly very good, being small, light, durable (high IP rating), lower end of the budget and with low running costs so in many these these devices would be great for most people.

The above is an example of how YOU can decide which is right for you.   In the example above the first decision was to remove all of the Fully Automatic defibrillators; you may personally prefer those for your situation.

The Heartsine devices have one of the most expensive pads but the longest shelf life so if the device is never used that increased cost is balanced by increased shelf life.   If the device is used regularly, the cost of replacing the pads is significant.

You may be limited by price so you may start be removing everything which costs above a certain threshold first.

Personally we use the Philips FR3 which is a fixed energy delivery device - one of the factors we ruled out early on in the above example but we have prioritized size and weight in our buying decision over the importance of energy delivery.

What is important is that your buying decision is appropriate to your situation and needs.


Training Defibrillators

Whilst all AEDs are broadly similar in operation, some have particular nuances; some are turned on by pressing the "on" button, some are turned on as soon as the lid is opened.   Some have the defib pads already connected, some pads have to be connected manually.   Within your budget factor in the cost of a training defibrillator which matches your model to increase the user's familiarity with that particular model and to develop their 'muscle memory' through training sessions. 

Live and Training AED


Further Reading

Should I have a defibrillator on my premises? 

Defibrillators in Remote Environments


  1. Stiell IG, Walker RG, Nesbitt LP, Chapman FW, Cousineau D, Christenson J, Bradford P, Sookram S, Berringer R, Lank P, Wells GA. (2007) "BIPHASIC Trial: a randomized comparison of fixed lower versus escalating higher energy levels for defibrillation in out-of-hospital cardiac arrest". Circulation. Mar 27;115(12):1511-7