EPIRB vs PLB Buying Guide: Which Emergency Beacon You Need
Quick answer: An EPIRB is registered to the boat, floats on its own, and transmits on 406 MHz for at least 48 hours. A PLB is registered to a person, fits in a pocket or life jacket, and transmits for at least 24 hours. For offshore boats the best setup is a Category I float-free EPIRB on the boat plus a PLB on each person who might end up in the water. Both must be registered with NOAA, free, and the registration renewed every 2 years.
When the engine is dead, the radio is out of range and the boat is taking water, a 406 MHz beacon is the one device that reliably reaches search and rescue from anywhere on the ocean. It sends your unique ID and GPS position to the COSPAS-SARSAT satellite system, which relays it to the Coast Guard, and a 121.5 MHz homing signal guides rescuers the final stretch. This guide explains the difference between EPIRBs and PLBs, which features matter, and how to mount, register and maintain them.
Step 1: Understand EPIRB vs PLB
| Feature | EPIRB | PLB |
|---|---|---|
| Registered to | The vessel | A person |
| Minimum transmit time | 48 hours | 24 hours |
| Floats on its own | Yes, antenna up | Some models, many need a flotation pouch |
| Automatic activation | Yes, Category I float-free or water activated | No, manual only |
| Size | Larger, bracket mounted | Pocket size |
| Best for | Boat sinking or capsizing offshore | Person overboard, tender, kayak, crew backup |
The key difference is this: an EPIRB stays with the boat, while a PLB stays with you. If someone goes overboard at night, the EPIRB in its bracket does not help them. If the boat sinks fast, a PLB in a drawer does not help anyone.
Step 2: Choose Category I or Category II
- Category I EPIRBs sit in a bracket with a hydrostatic release unit (HRU). If the boat sinks, water pressure at roughly 5 to 13 feet releases the beacon, which floats up and activates by itself. This is the right choice for offshore boats.
- Category II EPIRBs mount in a manual release bracket. They activate automatically when removed and placed in water, or manually, but someone must pull them out.
Mount a Category I unit outside, clear of hardtops, T-tops and rigging that could trap it as the boat goes down. Most HRUs must be replaced every 2 years. Check the date on the unit.
Step 3: Look for the features that speed rescue
- Built-in GNSS (GPS, often plus Galileo): sends a precise position within minutes. Essential on any modern beacon.
- AIS locator: newer EPIRBs also broadcast on AIS, so nearby boats with AIS see your position on their chartplotter.
- Strobe: helps rescuers spot you visually at night.
- Return Link Service: some Galileo-enabled beacons confirm on the unit that your alert was received.
- Battery life: typically 5 to 10 years before replacement by an authorized service center.
Step 4: Register and keep it current
In the U.S., register every 406 MHz beacon with NOAA SARSAT. It is free and required. Registration links your beacon ID to your boat, your contacts and your float plan details, which lets the Coast Guard confirm a real emergency and launch faster. Renew every 2 years and update it whenever you sell the boat, change phone numbers or change emergency contacts. A beacon bought used must be re-registered to you.
Step 5: Build the rest of your offshore safety kit
A beacon gets help moving, but you still need to talk to rescuers and be seen. Carry a DSC-equipped VHF, ideally a handheld in the ditch bag, and visual signals for the final approach. Our VHF radio guide and AIS guide cover the communication side. A ditch bag keeps the PLB, handheld VHF, signals and water together and ready to grab.
Step 6: Test it correctly
Use only the self-test function, following the manufacturer's instructions, and limit tests to what the maker recommends to preserve battery life. Never activate a beacon to test it. If you set one off by accident, turn it off and call the Coast Guard to cancel the alert.
Common EPIRB and PLB mistakes
- Not registering or letting registration lapse after selling the boat.
- Mounting the EPIRB under a T-top where it cannot float free.
- Expired HRU or battery. Check dates every season.
- Keeping the PLB in the console instead of on your life jacket.
- Confusing a SART with a beacon. A SART helps ships find a life raft on radar or AIS but does not alert search and rescue satellites.
Our picks for emergency beacons
All in stock at Boat Supplies Direct.
Personal locator beacon
McMurdo FastFind 220 PLB: GPS and Galileo positioning, strobe, 6 year battery life, at least 24 hours of 406 MHz transmission, and a flotation pouch included.
EPIRB mounting and hydrostatic releases
ACR HydroFix Hydrostatic Release Unit and the McMurdo G8 Replacement HRU Kit to keep a Category I bracket in date, plus the ACR LowPro V4 Category II Bracket for GlobalFix V4 owners. Confirm compatibility with your beacon model.
Ditch bag
ACR RapidDitch Express Bag keeps a PLB, handheld VHF and signals together and floating.
Life raft search and rescue transponders
ACR Pathfinder PRO SART or the McMurdo SmartFind S5A AIS SART for bluewater boats carrying a life raft, used alongside an EPIRB, not instead of one.
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Frequently Asked Questions
What is the difference between an EPIRB and a PLB?
An EPIRB is registered to the boat, floats and can activate automatically, and transmits for at least 48 hours. A PLB is registered to a person, is carried on the body, activates manually and transmits for at least 24 hours.
Do I need an EPIRB on my boat?
EPIRBs are not required on most recreational boats in the U.S., but they are strongly recommended for anyone running offshore beyond reliable VHF range. Commercial vessels often have carriage requirements.
Can I use a PLB instead of an EPIRB?
A PLB works on the same satellite system, but it has a shorter battery life, usually must be manually activated, and may need a pouch to float. It is a good backup, but an EPIRB is better protection for the vessel.
Do I need to register my EPIRB or PLB?
Yes. Registration with NOAA is required and free, and it must be renewed every 2 years. It gives rescuers your contact information and vessel details.
Is there a subscription fee for an EPIRB or PLB?
No. 406 MHz beacons use the government COSPAS-SARSAT system with no subscription. Satellite messengers are different products that do require a plan.
How often do I need to replace an EPIRB battery or HRU?
Most hydrostatic release units are replaced every 2 years, and beacon batteries every 5 to 10 years depending on the model. Check the dates printed on the unit.
This guide is general information. Register beacons with NOAA SARSAT, follow the manufacturer's instructions for mounting, testing and battery service, and check U.S. Coast Guard and local regulations for any carriage requirements that apply to your vessel.
