Every modern AED is “automatic” in the sense that the device decides whether to shock. The semi vs fully terminology refers to who delivers the shock once the device has decided: a semi-automatic AED prompts the rescuer to press a button; a fully-automatic AED delivers the shock without rescuer input. Both are safe, neither will shock a non-shockable rhythm. The decision comes down to one question: under stress, does removing the shock-button decision help or hurt?
Head-to-head comparison
| Dimension | Semi-Automatic | Fully-Automatic |
|---|---|---|
| Shock delivery | Rescuer presses the button | The device delivers automatically |
| Decision to shock | Device decides | Device decides |
| Shock therapy | Same | Same |
| Safety mechanism | Button press = bystanders clear | Voice countdown + warning |
| Best for | Trained workplace | Panic-likely / untrained-rescuer sites |
| Available on | Most major models | HeartSine 360P, ZOLL AED 3 variants |
The bystander clearance argument
Semi-automatic advocates point to one specific scenario: a bystander accidentally touches the patient just before the shock is delivered. With semi-auto, the rescuer can visually confirm “everyone clear” before pressing the button. With fully-auto, the countdown is shorter, and the rescuer has less time to verify. In practice, both AED types include voice warnings (“Stand clear, shock will be delivered in 3…2…1…”).
The freeze-under-stress argument
The opposing view: under cardiac arrest stress, untrained rescuers commonly freeze on the shock button, they hear “press the orange button” and hesitate. Fully automatic removes that decision point entirely. AHA 2020 guidelines accept both as appropriate; the decision is about the anticipated responder profile.
Verdict by use case
Best for trained workplace responders
Semi-Automatic AED (most major models)
Rescuer-controlled shock delivery. The button press serves as a final bystander-clearance verification. Default for trained workplace teams.
Recertified prices across all seven models
Recertified units are the same models under the same FDA premarket approvals, restored, tested and sold with a minimum three year warranty.
| Model | New | Recertified | You keep | Buy |
|---|---|---|---|---|
| Philips HeartStart OnSite | $1,589 | $875 | $714 (45%) | AED Leader or Response Ready |
| Philips HeartStart FRx | $2,099 | $875 | $1,224 (58%) | AED Leader or Response Ready |
| ZOLL AED Plus | $2,082 | $875 | $1,207 (58%) | AED Leader or Response Ready |
| ZOLL AED 3 | $2,399 | $1,150 | $1,249 (52%) | AED Leader or Response Ready |
| HeartSine Samaritan PAD 350P | $1,411 | $875 | $536 (38%) | AED Leader or Response Ready |
| HeartSine Samaritan PAD 450P | $1,761 | $875 | $886 (50%) | AED Leader or Response Ready |
| Cardiac Science Powerheart G5 | $2,157 | $1,225 | $932 (43%) | AED Leader or Response Ready |
Prices verified 30 September 2026 against the public product data of both stores. Both list identical recertified prices, so buy from whichever fits your order size: AED Leader for one to four units, Response Ready for five or more and for compliance and fleet programmes. New prices are the AED Leader list price on the same date.
The honest risk. A recertified AED is a used device. The three year minimum warranty is what makes the saving worth taking. Read recertified versus new and how to choose a refurbished AED before you decide.
Best for homes · churches · daycare · panic-likely sites
Fully-Automatic AED (HeartSine 360P et al.)
Removes the shock-button decision. For rescuers who may never have practiced or who freeze under stress, the automation eliminates a critical hesitation point. Voice countdown provides bystander clearance warning.
Frequently Asked Questions
Is a fully-automatic AED safer than a semi-automatic?
Same shock therapy. Safety depends on responder type, semi-auto for trained responders who’ll press deliberately, fully-auto for panic-likely scenarios.
Can a fully-automatic AED shock by accident?
No. It is designed to shock only shockable rhythms (VF and pulseless VT). Rhythm analysis is highly specific but not perfect, so always follow the prompts. All AEDs analyze first. The “automatic” refers to button-press elimination, not analysis bypass.
What if I touch the patient during a fully-auto shock?
Do not touch the patient once the AED says stand clear; contact during a shock can injure the rescuer. Follow the voice prompts and keep everyone clear.
Which AEDs are fully-automatic?
HeartSine PAD 360P ($1,651 new, $875 recertified at AED Leader) is the most common fully-automatic in the lay-user category. Fully automatic versions are also sold for the ZOLL AED Plus ($2,082), ZOLL AED 3, Powerheart G5, LIFEPAK CR2 and Defibtech Lifeline.
Should my home AED be fully-automatic?
Yes, recommended. Home rescuers are most likely to be the spouse, teenager, or family member without training. Fully-auto removes one hesitation point.
Models that come in both versions
Prices checked 30 September 2026 at AED Leader. Each link opens our full review with the buy path.
- ZOLL AED Plus review and price$2,082New, 5-year warranty (7 with ZOLL registration)
- LIFEPAK CR2 review and price$2,256 to $2,681New, 8-year manufacturer warranty
- Defibtech Lifeline AED review and price$1,478.80 to $1,659.15New, 8-year manufacturer warranty
Get your team certified the easy way.
Sources & References
- AHA, 2020 CPR & ECC Guidelines
- Manufacturer specs: HeartSine, ZOLL fully-automatic variants
Disclaimer: Educational comparison.
