Shelter · Home Security
Alarm systems. What they do, what they cost, and what they cannot do.
Monitored vs. self-monitored, entry sensors, glass-break detectors, false alarm prevention, and how to pick a system without overpaying or overcomplicating.
By Dan Whelan, founder of New World Survival
Researched from government agencies, university extension services, and other published sources. See our sources
What alarms do
An alarm system is a detection and notification layer, not a barrier.
Doors, windows, and lighting slow or deter an intruder. An alarm system detects that someone has passed those layers and notifies you, a monitoring center, or both. Research suggests that roughly 60% of would-be burglars are deterred by a visible alarm system, meaning the sign in the yard and the sticker on the window are doing real work before a sensor ever triggers.1
But the notification side of the equation is more complicated than the alarm industry suggests. An estimated 94% to 98% of residential alarm activations are false, caused by user error, pets, low batteries, or aging equipment. In response, many police departments have deprioritized or stopped responding to unverified alarm calls entirely.2
None of this means alarm systems are useless. It means they work differently than most people expect, and the value depends on what kind of system you choose, how you use it, and what your local police department will actually do when it triggers.
Monitoring options
Three ways to monitor your system.
Every alarm system detects the same events. The difference is who gets notified and what happens next.
Professional monitoring
A monitoring center staffed 24/7 receives your alarm signals. When a sensor triggers, the center verifies the alarm (typically by calling you) and dispatches police, fire, or medical services if the alarm is confirmed or if they cannot reach you.
Cost: About $20 to $33 a month for the major DIY brands as of October 2026, depending on the provider and features. Some require 1 to 3 year contracts; others are month-to-month.
Best for: Households that travel frequently, have irregular schedules, or want coverage during sleep when you cannot check your phone.
Self-monitored
You receive push notifications, text alerts, or app alerts when a sensor triggers. You assess the situation yourself, using camera feeds if available, and call 911 if needed. No monthly fee beyond any camera cloud storage subscription.
Cost: Free to $10 per month for camera cloud storage. No monitoring contract.
Best for: Households on a budget, people who are usually home or near their phone, and anyone who wants full control without a subscription commitment.
Hybrid
You receive all notifications on your phone and handle most alerts yourself. The monitoring center serves as a backup, stepping in if you do not respond within a set time window, or if the system detects a fire or CO alarm.
Cost: Varies. Some providers include this as a mid-tier plan at $15 to $25 per month.
Best for: Households that want to handle routine alerts themselves but want a safety net for emergencies and overnight coverage.
Insurance note: Homeowners insurance discounts for alarm systems typically range from 2% to 5% for a basic system and up to 15% for a professionally monitored system with fire and intrusion coverage. The average savings is roughly $100 per year, which may offset part or all of the monthly monitoring cost.3
Sensor types
The sensors that make up a system.
An alarm system is a collection of sensors connected to a hub. Most residential systems use three to five sensor types. Understanding what each one does helps you place them where they matter and skip the ones you do not need.
Door and window contact sensors
A two-piece magnetic reed switch. One piece mounts on the frame, the other on the door or window sash. When they separate, the circuit breaks and the alarm triggers.
Detects: A door or window being opened. Does not detect glass being broken while the window remains closed.
Where to place: Every exterior door. First-floor windows, basement windows, and any window accessible from a roof, porch, or ground level.
Glass-break sensors
An acoustic sensor that listens for the specific sound frequency pattern of shattering glass. A single sensor can cover an entire room, detecting breakage from any window within range.4
Detects: Glass being smashed. Does not detect a window being pried open or a screen being cut.
Where to place: Rooms with large ground-floor windows, sliding glass doors, or any glass panel large enough for a person to pass through. One sensor per room is usually sufficient.
Interior motion sensors
Passive infrared (PIR) sensors that detect body heat moving through a room. These serve as a second line of detection: if someone bypasses a door or window sensor, the motion sensor catches movement inside the house.
Detects: Movement within the sensor's field of view. Pets under 40 to 60 pounds can be filtered by pet-immune models.
Where to place: Hallways, stairwells, and rooms where an intruder would pass through to reach the rest of the house. Avoid aiming directly at windows, heating vents, or areas where pets roam.
Siren and keypad
The siren is the audible alert. Its primary purpose is startling the intruder and drawing neighbor attention. The keypad is where you arm and disarm the system, usually near the main entry door with an entry delay of 30 to 60 seconds.
Siren volume: Most residential sirens run 85 to 110 decibels. Loud enough to be uncomfortable indoors and audible from the street.
Keypad placement: Near the entry door you use most, at a height everyone in the household can reach. Additional keypads near the master bedroom and garage entry are common.
Smoke, CO, and flood sensors
Many alarm systems integrate environmental sensors alongside intrusion sensors. These can trigger the same notification chain: a smoke alarm trips the system, the monitoring center is alerted, and fire dispatch follows if you do not respond.
Why it matters: Environmental alarms are exempt from Enhanced Call Verification requirements. A fire or CO alert receives immediate dispatch without the two-call verification step that intrusion alarms require.
Worth noting: If you already have standalone smoke and CO detectors, adding system-connected ones is optional. The benefit is centralized monitoring and notification, not detection quality.
Camera integration
Cameras are not strictly part of an alarm system, but most modern systems integrate with indoor and outdoor cameras. When a sensor triggers, the system can pull up the relevant camera feed so you or the monitoring center can visually verify whether the alarm is real.
Why it matters: Visual verification changes police response. An alarm call backed by camera footage showing an actual intruder receives a priority response that an unverified sensor alarm does not.
Our cameras guide: Security cameras covers placement, storage, and what to do about Wi-Fi jamming.
Contact sensors and glass-break sensors are complementary, not interchangeable. Contact sensors catch someone opening a window; glass-break sensors catch someone smashing through it. A home with only contact sensors has a gap wherever glass is the easier entry point. A home with only glass-break sensors has a gap at every unlocked or pried-open window.4
The false alarm problem
94% to 98% of alarm activations are false.
This is the single most important fact about alarm systems that most buyers do not learn until after they own one. False alarms are not a flaw in your system; they are a systemic problem that shapes how police respond to every alarm call.2
Why it happens
User error is the most common cause. Forgetting to disarm before opening a door, entering the wrong code under pressure, or not closing a window fully before arming the system.
Pets trigger motion sensors. Even pet-immune models have weight and sensitivity limits that larger or more active animals can exceed.
Low batteries and aging equipment cause sensors to malfunction or send erratic signals. Wireless sensors typically need battery replacement every 3 to 5 years.
Environmental factors: drafts, curtains moving near motion sensors, insects walking across sensors, loose-fitting doors or windows that rattle in the wind.
Why it matters
U.S. police departments respond to over 36 million alarm activations annually, at an estimated cost of $1.8 billion. Each false alarm consumes roughly 20 minutes of two officers' time.2
The result: over 40% of residents in U.S. cities with populations above 50,000 live in areas where police will not guarantee a response to residential alarm calls. At least 26 cities, including San Jose, San Francisco, Seattle, Detroit, and Las Vegas, have stopped responding to unverified alarms entirely.5
Many jurisdictions now require Enhanced Call Verification (ECV): the monitoring center must make at least two phone calls to different numbers on the account before dispatching police. Departments that adopted ECV saw a 30% to 50% reduction in false-alarm dispatches within the first year.6
Most jurisdictions also fine repeated false alarms after three or four free ones a year, with the fine escalating on each additional call, according to the Department of Justice guide on false burglar alarms.
Choosing a system
What to look for and what to skip.
The alarm industry makes money on monthly monitoring fees and long contracts. That does not mean monitoring is a bad deal, but it means the sales process is designed to move you toward the most expensive option. Here is what actually matters.
Check your local police response policy first
Before paying for professional monitoring, find out whether your police department responds to unverified alarm calls. If they require video or audio verification before dispatch, then monitoring without camera integration has limited value. Your department's non-emergency line or website will have this information.
Cellular backup is worth having
A system that relies solely on Wi-Fi stops working during an internet outage, which is also when you are most likely to need it. Cellular backup sends alarm signals over the cell network, independent of your internet connection. Most monitored plans include it. For self-monitored systems, check whether the hub has a cellular radio or runs only over Wi-Fi.
DIY installation covers most homes
Modern wireless systems use adhesive-backed sensors, app-guided setup, and pre-paired components. Professional installation ($80 to $150) is worth considering for homes with complex layouts or hardwired systems, but for most single-family homes, DIY installation takes an afternoon and requires no tools beyond a screwdriver.
Avoid long contracts if you can
Some providers require 1 to 5 year monitoring contracts with early termination fees. Month-to-month plans cost slightly more per month but let you cancel if the service does not work for you or if you move. If you do sign a contract, read the cancellation clause before you commit.
Start with entry points, add sensors as you learn
A contact sensor on every exterior door and first-floor window, plus one glass-break sensor per room with large windows, covers the most common entry methods. Add motion sensors and additional zones after you have lived with the system for a month and understand the traffic patterns in your home. Buying a 20-sensor kit on day one often leads to poorly placed sensors and more false alarms.
Realistic costs
What you will actually spend.
Equipment, monitoring, and the ongoing costs that add up. These ranges reflect the market as of 2026 across major national and regional providers.7
$100 - $400
Budget DIY systems
Self-monitored or optional monitoring. Hub, 4 to 8 contact sensors, 1 motion sensor, 1 keypad. Brands like Ring, Wyze, and SimpliSafe fall here.
Monthly monitoring: $0 to $20. No contract required for most.
$300 - $600
Mid-range systems
Professional monitoring included. Hub with cellular backup, 6 to 12 sensors, glass-break detectors, optional cameras. ADT, Abode, and Cove are typical providers.
Monthly monitoring: $20 to $35. Contracts of 1 to 3 years are common.
$600 - $1,200+
Premium and custom
Professionally installed. Full sensor coverage, integrated cameras, smart home automation, and premium monitoring. Vivint, Frontpoint, and local security companies are typical providers.
Monthly monitoring: $30 to $50+. Longer contracts and professional installation fees ($80 to $200) are typical.
Total first-year cost for a mid-range system with professional monitoring: roughly $600 to $1,000 (equipment plus 12 months of monitoring). Subtract the insurance discount (typically $50 to $150 per year), and the net cost is $450 to $950 in the first year, dropping to $240 to $420 per year in subsequent years when only the monitoring fee remains.
Before you buy
Questions to answer before you shop.
Answering these first prevents the most common buying mistakes: overpaying for monitoring nobody responds to, buying sensors you do not need, or signing a contract you cannot exit.
Does your local police department respond to unverified alarm calls?
Call the non-emergency line and ask. If they require video verification, factor cameras into your system cost. If they do not respond at all, self-monitoring with cameras may be more practical than paying for professional monitoring.
How many exterior doors and accessible windows does your home have?
Count them. This determines how many contact sensors you need and gives you a realistic equipment cost before you start looking at packages.
Do you have pets that will move through the house when the system is armed?
Pets over 40 to 60 pounds may trigger standard motion sensors. You will need pet-immune motion sensors, or you can skip interior motion sensors and rely on perimeter sensors (contact and glass-break) instead.
Will everyone in the household learn the system?
User error is the leading cause of false alarms. Every person who enters and exits the house needs to know how to arm, disarm, and respond to an accidental trigger. A system that only one person understands will generate false alarms every time someone else comes home.
Does your municipality require an alarm permit?
Many cities and counties require a permit to operate a residential alarm system, typically $25 to $50 per year. Operating without one may result in fines or police refusal to respond. Your city's code enforcement or police department website will have this information.
What is the contract length and cancellation policy?
Read the terms before signing. Early termination fees can range from the remaining balance of the contract to a flat fee of $100 to $500. Month-to-month plans avoid this entirely.
Common mistakes
Five mistakes that waste money or create problems.
Assuming professional monitoring means guaranteed police response
Monitoring centers dispatch calls, but they cannot control police response times or policies. In cities with verified-response ordinances, an unverified alarm call may be classified as a low-priority event that takes 40 minutes or more to reach, if police respond at all. Know your local policy before you pay for monitoring.
Buying the largest sensor package without counting your entry points
A 20-sensor kit sounds like good value, but if your home has 3 doors and 8 accessible windows, you only need 11 contact sensors plus a few glass-break sensors. Extra sensors placed where they are not needed create more opportunities for false alarms. Count your entry points first, then buy the sensors to cover them.
Ignoring false alarm fines until one arrives
Many municipalities charge $50 to $250 per false alarm after an initial grace period. Three false alarms in a year can cost more than the monitoring subscription. Register for an alarm permit if required, learn to arm and disarm correctly, and test sensors quarterly to keep false alarms rare.
Relying entirely on a yard sign without installing a system
Yard signs and window stickers do deter opportunistic burglars, and some people install them without an actual system. This works until someone tests the claim. A sign with no system behind it is a bluff that cannot call for help, cannot record what happened, and cannot alert you that someone entered your home while you were at work.
Skipping the household training
The week after installation is when most false alarms happen. Every person in the household needs to practice arming, disarming, and canceling a false alarm. Children old enough to come home alone need to know their code and the entry delay timing. House sitters and dog walkers need temporary codes or clear instructions. An alarm system that the household cannot operate smoothly is an alarm system that will be left unarmed.
Related guides
Alarms are one layer.
An alarm system works best when the layers in front of it are solid: good locks, good lighting, and daily habits that reduce opportunity.
The Layers of Home Security
The full framework. Alarm systems are one layer among several; context for every upgrade.
Door Security
Deadbolts, strike plates, and frames. The physical barrier layer that an alarm detects being breached.
Window Security
Window locks, security film, and glass-break sensors. The entry points that contact sensors and glass-break detectors protect.
Lighting and Visibility
Motion sensors, lumen ranges, and placement strategy. The detection layer that works alongside alarm sensors.
Security Cameras
Placement, storage, and jamming. Camera footage is what turns an alarm into a verified call.
Common questions
The questions that come up most.
Is a monitored alarm system worth the monthly cost?
It depends on your situation. Professional monitoring from the major DIY brands runs about $20 to $33 a month as of October 2026 and provides 24-hour response when you cannot answer an alert yourself: asleep, traveling, or at work. Insurers usually take at least 5 percent off for a burglar alarm, and some cut premiums by as much as 15 or 20 percent for a system monitored by a central station, according to the Insurance Information Institute; ask your insurer what it credits before you buy. Because most alarm calls are false, 20 to 25 U.S. cities require the monitoring company to verify a burglar alarm before police respond, so the value of monitoring depends partly on your local department's policy. Self-monitored systems with smartphone alerts and camera verification are a lower-cost alternative if you can respond quickly yourself.
What is the difference between a door sensor and a glass-break sensor?
A door or window contact sensor uses a two-piece magnetic reed switch: one piece on the frame, one on the door or sash. When they separate, the circuit breaks and the alarm triggers. These sensors detect a door or window being opened, but they do not detect glass being broken while the window stays closed. A glass-break sensor listens for the specific sound frequency of shattering glass and can cover an entire room from a single sensor. The two types are complementary: contact sensors catch someone opening a window, and glass-break sensors catch someone smashing through it.
How can I avoid false alarms with a home security system?
Between 94 and 98 percent of burglar alarm activations are false, according to the Department of Justice guide on false burglar alarms. The leading causes are user error, faulty or poorly chosen equipment, and poor installation. To reduce them: practice arming and disarming until it is automatic, replace sensor batteries on a schedule rather than waiting for low-battery alerts, keep motion sensor paths clear of pets and moving objects, use entry delays long enough to reach the keypad comfortably, and test every sensor after installation and quarterly afterward. Most jurisdictions allow three or four false alarms a year before fines begin.