Where to Place an Ultrasonic Pest Repeller

Think of the device as a lamp, not a radio. A radio fills a house from anywhere; a lamp only lights what it can see.

Every rule below follows from that one idea.

The four rules that matter most

1. Clear line of sight to open floor. The device needs to face the space you're protecting with nothing in front of it. Behind a sofa, inside a cupboard, or blocked by a bin means the sound never reaches the runway.

2. One device per enclosed space. A closed door is a wall. If you want the kitchen, the living room and a bedroom protected, that's three devices — not one in the hallway. See do ultrasonic repellers work through walls for the physics.

3. Low is better than high. Rodents travel at floor level, hugging skirting boards. A socket 20–40 cm off the ground puts the emitter in the same plane as the animal. A socket at worktop height sends most of the output over their heads.

4. Continuous operation. These devices work by making an area permanently unpleasant, which only happens if they're permanently on. Switching one off at night defeats the entire mechanism.

Room by room

Kitchen

The kitchen is almost always the reason rodents are in the building at all — it has food, water and warmth in one place.

Place the device on a wall socket with the emitter facing the open floor, ideally on the wall opposite the appliance run. The routes you're targeting are the plinth gap under the units, the void behind the fridge and the space behind the oven.

Avoid: sockets behind the kettle, the bread bin or a knife block; sockets inside a cupboard; and the socket directly behind the fridge, where the device is enclosed by the appliance itself.

Pair it with sealed food containers. A repeller competes badly with an open bag of rice.

Living room and hallway

Living spaces are transit rather than destination — animals cross them to reach food. Face the device down the length of the room, along the wall line rather than into the middle of the floor.

Hallways matter more than people expect. A hallway is the junction of every route in the house, and a device there covers a lot of traffic — but only for the hallway itself, not the rooms leading off it.

Avoid: behind the sofa, behind long curtains, or under a console table. Soft furnishings absorb ultrasound very effectively; a curtain in front of the emitter is close to a wall.

Bedrooms

Use the socket furthest from soft furnishings, facing across the floor rather than into the base of the bed. Under-bed storage boxes and hanging duvets create acoustic shadows across most of the room.

If a family member is a teenager or unusually sensitive to high frequencies and reports hearing a faint tone, move the device to the hallway side of the room or choose a model with a higher minimum frequency.

Garage, cellar and storeroom

These are the highest-value locations in most homes, and the most commonly ignored. They're dark, undisturbed, connected to the outside, and full of cardboard.

Place the device with sight of the door threshold — the most likely entry — and of the main floor aisle. If the space is more than about 40 m² or is heavily shelved, shelving units act as walls and a second device on the opposite aisle is worth it.

Do this before you have a problem. A garage is the cheapest room in the house to protect preventively.

Loft and roof space

If you've heard scratching overhead, this is where it's happening. Loft sound behaviour is unusual: joists, boxes and insulation break the space into acoustic compartments.

Position near the access hatch facing along the main joist run, and add a second unit at the far end if the loft is longer than about 10 m. Note that loft insulation absorbs ultrasound strongly — expect a loft to need more coverage than its floor area suggests.

Outbuildings, sheds and open ground

Indoor plug-in devices are the wrong tool outdoors: no mains socket, no enclosure to hold the sound, weather exposure. Outdoor protection needs a weather-rated, solar or hybrid-powered unit designed for open ground — and for burrowing species such as moles and voles, a device that also transmits vibration into the soil rather than sound into the air.

How many devices do I actually need?

                           

Property	Realistic device count
One-bed apartment	2 — kitchen and living area
Three-bed house	3–4 — kitchen, living area, plus loft and/or garage
House with cellar or large garage	4–5
Detached house with outbuildings	Indoor set plus a dedicated outdoor unit

If a manufacturer tells you one plug-in unit covers a whole house, they're describing a floor area, not an acoustic reality. We'd rather sell you the right number than sell you one and lose your trust in month two.

Six placement mistakes that make a good device useless

1.  
2. Behind furniture. The single most common error. It doesn't attenuate the output — it removes it.
3.  
4. Inside a cupboard. Enclosing the emitter protects the cupboard and nothing else.
5.  
6. One unit for a multi-room home. Doors and walls are boundaries, not obstacles.
7.  
8. Too high. Above about 1 m, most output passes over the animals entirely.
9.  
10. Switched off at night or when away. Night is when the traffic happens, and an empty house is when a habit re-forms.
11.  
12. Moved every few days. Constant relocation prevents any area from becoming consistently unpleasant. Choose the position, then leave it for at least a month.

What to expect once it's in place

Run it continuously and give it four weeks before you judge it.

If nothing has changed by week five, the problem is almost always one of the six mistakes above — or a food source or entry point still doing more work than the device can undo. Our inspection guide covers finding those.