Alarm systems: self-monitored, monitored, or professionally installed

Alarm systems come in three broad arrangements, and the marketing for each is written as though the other two do not exist. The right answer depends on what you actually want to happen when the alarm goes off — which is a question most people have not consciously answered.

Start there and the rest follows.

Ask what you want to happen

Four possible outcomes, and each implies a different system.

“I want to know.” A notification to your phone, and you decide. This is what most households actually want, and a self-monitored system delivers it.

“I want the intruder to leave.” A siren, visible sensors and lighting. Deterrence, which does not require monitoring at all.

“I want someone to attend.” Professional monitoring with a keyholder or guard response service.

“I want the police to come.” This is the one to be realistic about. In most countries the police do not respond to unverified domestic alarms, and where they do respond to monitored alarms it is usually only for systems meeting a specified standard, often registered, and frequently after confirmation from two detectors or from audio or video. An unmonitored siren does not summon anyone.

Being honest about which of these you want prevents both overspending and disappointment.

The three arrangements

Self-monitored

Sensors, a hub, a siren, notifications to you. No monthly fee, or a small one for cloud storage.

Suits: most households, particularly those already running a smart home, where the alarm is a set of rules over sensors you have for other reasons.

Strengths: no ongoing cost, complete flexibility, integration with lighting, locks and cameras, and you own the data.

Weaknesses: nobody responds if you are asleep, abroad or in a meeting. No professional escalation. Insurers rarely recognise it.

Professionally monitored, consumer system

A consumer product with a paid monitoring plan. A centre receives alarms and follows an agreed procedure.

Suits: households wanting escalation without a full installed system.

Strengths: someone always responds, usually reasonable cost, keeps the convenience of a consumer app.

Weaknesses: ongoing fee, may not meet the standard your insurer or local police require, and you are dependent on the provider continuing to operate.

Professionally installed and monitored

A graded system installed by a certified company to a recognised standard, with contracted monitoring and often keyholder response.

Suits: higher-value properties, insurance requirements, and anyone who wants a documented and certified installation.

Strengths: meets insurance conditions, may enable police response where that exists, professionally designed coverage, maintained and certified.

Weaknesses: most expensive to install and run, least flexible, often proprietary and hard to integrate with the rest of your house, and you may not be able to modify it yourself.

Grades and standards, briefly

European alarm systems are classified by grade under the EN 50131 series, reflecting the level of threat they are designed to resist. Grade 1 is the lowest, Grade 2 is typical for domestic property, Grade 3 for higher risk, Grade 4 for high security.

Why it matters: insurers and police response schemes reference these grades, and a consumer system is generally not graded at all. If an insurance policy specifies a graded system, a self-installed one will not satisfy it regardless of how good it is.

If insurance compliance is your reason for buying, get the requirement in writing from your insurer before choosing anything. Policy wording varies, and we have seen people buy the wrong category twice.

Designing the sensor coverage

Whichever route you take, the design principles are the same.

Perimeter first. Contacts on external doors and accessible windows detect entry before anyone is inside, which is earlier than motion can manage.

Interior confirmation. One or two motion sensors covering likely routes. The combination of a perimeter breach followed by interior movement is a far stronger signal than either alone, and confirmation is what removes most false alarms.

Cover the least overlooked entry point, which is where an opportunist will go.

Do not forget the garage and its internal door, which is a common weak point out of sight from the street.

Protect the hub itself. A panel by the front door that can be smashed on entry should have a delay, an anti-tamper alarm and, ideally, be somewhere less obvious.

Sirens both inside and out. Interior noise is genuinely unpleasant and encourages leaving; an exterior sounder alerts neighbours.

Think about pets at design stage rather than afterwards, using pet-immune sensors or relying on contacts in the rooms they use.

The things that decide whether it stays switched on

An alarm that is not armed protects nothing, and the commonest reason people stop arming is friction.

Arming must be trivial. A button by the door, a code on a keypad, automatic on the house becoming empty. If it requires opening an app, it will not happen consistently.

Entry and exit delays long enough to get in and disarm without panic.

A night mode arming the perimeter while allowing movement upstairs. This is the mode most households use most and the one most often not configured.

Clear feedback on whether it is armed, visible without a phone.

Low false alarm rate, which comes from confirmation rules, sensible sensor placement and pet consideration. Three false alarms and a household stops arming.

Everyone has their own code, so the log is meaningful and access can be revoked.

Wireless or wired sensors

A practical choice that affects both reliability and what is possible in an existing house.

Wired sensors are supervised continuously, need no batteries, and cannot be jammed by radio interference. They are standard in professionally installed systems and impractical to retrofit without lifting floors and chasing walls.

Wireless sensors retrofit in minutes, cost less to install, and bring batteries and radio to think about. Good systems supervise them — each sensor checks in periodically, and a sensor that stops reporting raises a fault rather than silently doing nothing. Supervision is the specification that separates a real wireless alarm from a set of sensors: an unsupervised wireless sensor with a flat battery is indistinguishable from a working one.

Jamming deserves a fair mention. Deliberate radio jamming of a wireless alarm is possible and is not what happens in typical domestic burglary, which is opportunistic. Systems designed to a graded standard include jamming detection; consumer systems vary. It is a reasonable consideration for a high-value property and not a reason for most households to reject wireless.

Our view for an existing house: wireless with proper supervision, batteries diarised, and a wired sounder if you can manage one.

Fire, water and the other things worth adding

An alarm system built around intrusion is covering the least likely of the risks to a home. The same hub can cover the others for very little.

Interlinked smoke and heat alarms reporting to the same system, so a fire in an empty house reaches you.

Carbon monoxide detection where anything burns fuel.

Leak sensors behind appliances and under sinks, ideally closing a shut-off valve.

Low temperature alerts where pipework runs through cold space.

Mains power loss, which silently ends heating, freezing and monitoring at once.

Statistically these will do more for you than the intrusion detection will, and if you are buying a hub and sensors anyway, adding them is marginal cost.

What we would build for a typical house

1. Contacts on every external door and accessible ground-floor windows.
2. Two interior motion or presence sensors on likely routes.
3. Confirmation rule: perimeter breach plus interior movement within a short window equals a genuine alarm.
4. Interior siren and an exterior sounder.
5. Lighting response: everything on at full brightness on a confirmed alarm.
6. A visible camera at the main approach, recording locally.
7. Night mode and away mode, both armable from a physical control by the door.
8. Backup power and a backup notification path if genuine detection matters — a small uninterruptible supply and, on a monitored system, a mobile data module.

Then add professional monitoring if you want someone to respond, and get a graded installed system if your insurer requires one. Those are decisions about response and compliance, not about detection — the sensor design above is the same either way.