Why it beats a cloth
A cloth fills up after a window or two, and then you're spreading water around the glass. Wet cloths left on a radiator put the water straight back into the room. A window vac collects the water in a tank you empty once, down the sink, so it leaves the house.
It also gets into the bottom edge of the frame, where water collects and where black mould starts on the seals. Clearing that line every morning is one of the simplest ways to stop it. See black mould on window seals.
What to look for
- Battery run time. Long enough to do every window in the house, plus the bathroom tiles or mirror, on one charge.
- Tank size. On a cold morning with a lot of condensation, a small tank may need emptying before you finish. A bigger tank means fewer trips to the sink.
- Blade width. A wide blade clears big panes and patio doors in fewer strokes. A narrower one gets into small window panes and the corners of the frame more easily.
- A tank that comes off and rinses out. Condensation water picks up dust and grime from the frame, so the tank needs a rinse now and then to stay clean.
- Spare or replaceable blades. The rubber edge wears over time and starts to leave streaks.
Our picks
These are chosen by their specs against the list above. We haven't tested them ourselves; the reasons say which spec puts each one here.
For most homes
Kärcher WV 2 Plus N
- Type
- Cordless
- Tank
- 100ml
- Battery
- 35 minutes
Rated to run for 35 minutes on a charge, and battery time is what counts when you do every window in one go. Its tank holds 100ml, so on a very wet morning you may need to empty it once before you finish.
For big windows and patio doors
Tower Cordless Window Vac T131001
- Type
- Cordless
- Tank
- 150ml
- Battery
- 30 minutes
The bigger 150ml tank suits large panes, where there's more water to collect before you reach the sink. The battery is rated for 30 minutes, so charge it between uses rather than letting it run low.
How to use one on condensation
- Do it first thing, before the water runs down onto the sill and frame.
- Start at the top of each pane and pull the blade down in overlapping strokes.
- Run it along the sill and the bottom edge of the frame, where the water collects.
- Empty the tank into the sink, so the water leaves the house instead of drying back into the room.
- Rinse the tank now and then, and leave it open to dry.
- Put it back on charge so it's ready for tomorrow.
When a window vac isn't enough
A window vac clears the water you can see. It doesn't lower the humidity in the room, so if the windows stream every morning, or the walls and corners are damp too, the air needs drying as well. Start with ventilation and a steady background heat, and add a dehumidifier if the room stays damp.
Why windows get wet every morning, and how to stop it.
Dehumidifier size calculator If the windows still stream every morning, find the dehumidifier size that suits your home.