An opening sensor is one of the cheapest pieces of security equipment that exists. The question, therefore, is not really about the budget, but about knowing where to put it. Because most people buy one, not six, and a sensor placed on the wrong opening is almost useless.
What the data says about break-in methods
Insee, based on the Living Environment and Security survey conducted with the Ministry of the Interior's statistical service, has published the breakdown of methods used against households that are victims of burglary. The result is clear: for 64% of victim households, a door was forced or an attempt was made to force it. Breaking a window comes in far behind, at 23%, and climbing a balcony or fence at 18%.
Two honest clarifications regarding this figure. First, it concerns the share of victim households, not successful burglaries: a failed attempt on a door counts as much as a successful break-in. Second, the data dates from the 2018 survey, published in 2021, and this survey has since been replaced by another. The order of magnitude remains useful; the decimal does not.
The same statistical work provides a second, more encouraging element: for 55% of victim households, the burglary did not succeed and stopped at the attempt stage. More than half the time, something caused the operation to fail.
The short answer: the door
If you only equip one opening, it should be the front door. Not because it is inherently more fragile than a window, but because it is the passage most thieves choose. A door is discreet to work on from a landing or a recess, it does not make noise from shattering glass, and it allows for exiting with hands full without attracting attention.
The wireless opening sensor sticks to the frame and the door, in two aligned parts. As soon as the two separate, the alert is triggered. There is nothing to drill, nothing to wire, and removal leaves no trace, which matters if you are renting.
Cases where the window takes priority
National statistics describe an average, not your home. Three situations reverse the priority. A ground floor where the windows overlook a courtyard, an unenclosed garden, or a quiet alleyway: here, the window becomes the most discreet access point, and often the least securely closed. A bathroom or kitchen window that is systematically left ajar for ventilation, even when leaving: an unclosed opening does not need to be forced. And a patio door or French window on a terrace, which combines the worst of both worlds: a large glass surface and access hidden from view.
The sensor is the same object in all cases. It does not distinguish between a door leaf and a window sash; it detects a separation between two elements. This is what allows it to be moved from one opening to another depending on the season or what you discover through use.
What a sensor does, and what it does not do
It signals an opening. It does not prevent it. A sensor does not reinforce any lock, does not block any door, and does not slow anyone down. Its value lies entirely in the time it saves you: knowing right away, rather than when you return in the evening.
It also does not replace basic measures. The Ministry of the Interior reminds us in its burglary prevention guide that it is necessary to equip your door with a reliable locking system and lock it twice, even when you are at home. A sensor placed on a door that you slam without locking is just monitoring an open door.
A second opening, rather than a second type of device
For those who want to go further, the most cost-effective move is not to add a new category of product, but a second sensor on the home's second most important opening: the most accessible window, the communicating garage door, or the terrace patio door. Two covered access points for the price of two sensors is what comes closest to real coverage at this budget level.
The corresponding product
The Discreet Opening Sensor — Door & Window works via WiFi, without a hub or subscription, and can be installed on both a door and a window. To place it within the rest of the range, see the sensors or the full catalog.
To go further
For a rented property where nothing can be drilled, see our 5 solutions without drilling. And for what happens before the intruder reaches the door, the outdoor camera.