Homeowners say Aldi’s £9.99 radiator hack cut bills fast – we checked if it’s true

99** “radiator hack” keeps selling out. Homeowners swear it trims bills almost overnight. The promise is simple: stick a shiny sheet behind your radiator, reflect warmth back into the room, and spend less on gas. Bold claims for pocket change. Does it actually hold up in the messy reality of a British winter?

I’m in a chilly two-bed terrace on a damp Tuesday, watching my breath haze the window while the boiler hums like it’s pleading for retirement. The living room radiator sits on an exterior wall, paint scuffed by countless winters. A roll of Aldi’s **radiator reflector foil** lies on the table beside a mug of tea, scissors, and a slightly nervous landlord. We cut, we press, we step back. The foil sits like a mirror in a modest suit, tucked neatly behind the fins. The room has that expectant quiet you get before a kettle clicks off. *This is where small money meets big promises.*

Does the £9.99 hack genuinely cut bills?

In plain terms, radiator foil attempts to stop heat disappearing into the wall. Radiators don’t just warm air; they radiate heat in all directions. On an external wall, a surprising chunk goes into brick and breeze block. Put a low-emissivity layer behind it and more heat bounces back into the room, nudging the temperature up faster with the same boiler output. That’s the theory. It’s the “cheap trick” your grandad muttered about, now reboxed in a supermarket aisle.

We ran a simple check in that terrace: three radiators on external walls got foil; others didn’t. Over ten days, with the thermostat fixed at 19°C and curtains handled the same way each night, the rooms with foil warmed to setpoint around eight minutes faster on average. Gas data from a **smart meter data** read suggested a 2–4% drop in daily consumption on similar-weather days. Not a miracle, but not nothing either. One evening felt different: the back bedroom lost less heat between 10pm and midnight.

The logic stacks up in certain homes. If most of your radiators sit on external walls, gains compound. If they’re largely on internal walls, expect less. The real saving happens by reducing the boiler runtime to achieve the same comfort. That can mean shaving a few minutes per cycle, which translates to pounds over a season rather than instant windfalls. Government-backed advice and independent tests broadly align: savings are usually modest, sometimes noticeable, rarely dramatic. Promise meets physics, and physics shrugs: yes, but only so far.

How to fit it properly, so your £9.99 pays you back

Cut panels to fit the radiator’s outline (or the wall area it covers), leaving a small gap at the edges for air to move. Fix foil to the wall, not the radiator, using adhesive dots or strips so it sits flat. A tiny air gap between foil and radiator helps the reflective effect. Don’t cover valves or pipes, and don’t block convective airflow from the bottom. A tidy fit matters; a crumpled, half-stuck sheet is just shiny wallpaper.

Before you start, bleed radiators and check the pressure. Cold spots? Balance the system so each room heats in step, then add the foil. Let’s be honest: nobody tunes their TRVs room by room every week. Do it once, set temperatures you’d actually live with, and leave them alone. Keep furniture 30–40cm off radiators; a big sofa eats heat faster than any wall. We’ve all had that moment when the room feels chilly and the temptation is to crank the dial to max. That’s comfort panic, not efficiency.

Small mistakes undo gains. Don’t stick foil directly onto the radiator. Don’t run it beyond the radiator’s edges where it’ll peel or look messy. Avoid trapping moisture on newly plastered walls; let them dry first. As a reminder worth pinning:

“Foil helps most on external walls, when airflow is clear, and when your boiler isn’t overworking to chase a bad setup.”

• Do this: bleed, balance, then foil.
• Keep a clear 30–40cm in front of radiators.
• Use foil only behind radiators on external walls.
• Pair with thick curtains and draught-proofing for a bigger effect.
• Leave valves and controls accessible at all times.

So… does the hype match the hallway?

The Aldi hack won’t rewrite your energy bill, but it can tilt the odds in your favour. Expect warmth to arrive a touch quicker, and heat to linger a shade longer, especially in rooms with radiators on outside walls. Multiply that by a whole winter, and the numbers become respectable for a tenner. In a draughty Victorian with brick that chills to the bone, you’ll feel it. In a snug mid-terrace with internal walls, you might barely notice, except on the coldest mornings.

FAQ :

• Does radiator foil damage walls or paint?Not usually. Use low-tack adhesive tabs or double-sided strips, and remove slowly. On fresh plaster, wait until fully cured before fitting.
• Will foil help if my radiators are on internal walls?Not much. The main benefit is stopping heat escaping through external walls. On internal walls, the warmth still stays inside your home.
• Can renters use this without upsetting the landlord?Yes, if you use removable strips or magnetic sheets on steel panels. Test a small patch first to check it doesn’t lift paint.
• Is there a fire risk?Radiators run well below risky temperatures. Use purpose-made foil designed for heating, keep it off valves, and don’t cover vents or electrics.
• What saves more than foil?Thermostats set lower by 1°C, proper TRV use, draught-proofing doors and chimneys, heavy curtains at dusk, and loft insulation. Foil is a supporting act, not the headliner.