Car alarms and security devices range from basic factory-fitted immobilisers to sophisticated Thatcham-rated S5 GPS tracking systems. Understanding the different security categories, what they protect against and how they affect insurance premiums helps vehicle owners choose appropriate protection.
Factory vs Aftermarket Alarms
Factory-fitted alarms are standard on most new cars sold in the UK and meet the minimum SRA (Security Registered Assembler) standard required by insurers. While effective against opportunistic theft, factory alarms typically offer less sophisticated protection than professional aftermarket systems. Aftermarket alarms can offer higher specification protection, more configurable features and greater insurer recognition.
Thatcham Security Ratings Explained
Thatcham Research rates vehicle security products on a category basis for insurer recognition. Category S5 is the highest standard, requiring a GPS-connected tracker with 24-hour monitoring, automatic theft detection and location, driver recognition tags (preventing relay attacks) and police partnership for recovery. Category S4 adds automatic engine immobilisation to a high-specification alarm system.
Category S5 trackers including Scorpion Track, SmarTag, Trackstar and Vodafone Automotive provide the most comprehensive protection and qualify for the highest insurance discounts of 10 to 20 percent on comprehensive premiums.
Insurance Discounts for Security Devices
Installing a Thatcham S4 or S5-rated alarm system qualifies for insurance premium discounts of 7 to 20 percent on comprehensive cover. For a vehicle with a 1,000 GBP annual premium, a 15 percent discount represents a 150 GBP annual saving. S5 GPS trackers cost 300 to 600 GBP for installation plus 100 to 200 GBP annual monitoring, but the combined insurance saving and theft risk reduction often make them cost-effective for vehicles valued over 20,000 GBP.
Frequently Asked Questions
What is the difference between a car alarm and an immobiliser? A car alarm sounds a siren and flashes lights when triggered by sensors detecting break-in attempts. An immobiliser prevents the engine from starting without the correct key or disarm code. Many modern systems combine both functions.
How much does a Thatcham S5 tracker cost? S5 GPS trackers cost 300-600 GBP for initial installation plus 100-200 GBP annual monitoring subscription. They qualify for 10-20 percent insurance discounts on comprehensive cover.