A pyrolytic cycle burns cavity grime to ash at roughly 400–500°C over 1.5–3 hours, but the racks, runners, door glass and extractor stay dirty. That gap is why plenty of pyrolytic owners still book a £77 professional clean.
How a pyrolytic cycle works
Pyrolysis is controlled burning. The oven locks its door, heats the empty cavity to somewhere between 400°C and 500°C (Bosch quotes 485°C on its UK models) and holds it there until every fat splash and pie drip has carbonised into pale grey ash. Once the cavity has cooled enough for the lock to release, the ash wipes out with a damp cloth.
Most ovens offer three levels. Neff's light programme runs about 1 hour 15 minutes and its intensive setting around 2 hours; Bosch says 1.5 to 2.5 hours depending on soiling, and the door stays locked while everything cools. Which? measured the average cycle at about 5kWh of electricity, roughly £1.30 at current unit rates. Manufacturers describe pyrolysis as a deep clean for every 6–12 months rather than a weekly habit.
What the cycle leaves dirty
Read the manual before pressing start and you meet the catch. Everything removable has to come out first: wire shelves, side rails, telescopic runners, baking trays. Standard chrome racks discolour at pyrolytic temperatures and sliding runners seize once the heat burns off their lubricant, so unless yours are rated to stay in (Miele sells PyroFit racks and runners for exactly this), the dirtiest items in the oven end up in your sink with a scourer.
The door is the other blind spot. The cycle burns the inner face of the glass clean, but grease that has crept between the panes sits outside the sealed cavity, where the heat can discolour it without removing it. Manuals also tell you never to scrub the door seal, and a tide line of cooked-on grease usually survives just outside the gasket.
The ash still needs wiping out.
And nothing around the oven changes. The extractor mesh and the hob carry the same film of airborne fat that built up inside the cavity, and no cycle reaches either of them.
The cavity comes out grey and powdery. The racks come out exactly as dirty as they went in.
Catalytic liners are a different system
Callers often say self-cleaning when they mean catalytic, and the two behave very differently.
- Pyrolytic cleaning
- A locked, timed cycle at 400–500°C that turns residue on every surface inside the cavity to ash. Fitted to dearer built-in ovens. You run it deliberately, a few times a year.
- Catalytic liners
- Rough, porous panels that absorb grease and oxidise it during normal cooking above about 200°C. They work continuously but only where fitted: often just the back wall, sometimes the sides and roof too. The oven floor and the door are always bare enamel you clean yourself.
Liners carry two further limits. They deal with grease but leave sugar spills alone, and they cannot be scrubbed, because abrasives and caustic sprays wreck the coating. After enough years the panels saturate and stop absorbing, and replacement is the only fix.
Where the £77 professional clean fits
A professional visit exists for the parts pyrolysis is designed to ignore. On a professional oven clean we carry a heated dip tank in the van: racks, runners, trays and the grill pan soak in it while the cavity and door glass are degreased by hand with non-caustic products, and the door comes apart where the design allows, so the grease between the panes goes too. The oven is heat-tested before we leave, there is no smell, and you can cook the same evening. A single takes about 90 minutes.
Prices are fixed when you book on 020 8077 5225, seven days: £77 for a single oven, £110 for a double, and while we are there the hob is £23–28 and the extractor £28. The full list is on the prices page.
Moving out of a rented flat is the clearest case for booking one even on a pyrolytic oven: the checkout clerk photographs the racks, the runners and the door glass rather than the cavity walls, which is exactly the kit the cycle never touches and exactly where deposit money gets docked, as we set out in our guide to oven cleaning and deposits. A neglected oven is the second: one cycle rarely shifts years of hardened carbon, and repeating it with the kitchen smoking each time is a grim afternoon. Birds in the flat, a kitchen you cannot ventilate, or an Aga, which has no self-clean at all, point the same way.
The split that works for most owners is simple. Let the cycle keep the cavity presentable through the year, and book a hand clean when the racks, runners, glass and extractor have fallen behind the walls. A fair share of the pyrolytic ovens we open across London belong to people who ran the function twice, minded the smell, and quietly stopped.
Pyrolytic cycle and professional clean side by side
| Job | Pyrolytic cycle | Professional clean |
|---|---|---|
| Cavity walls and roof | Burnt to ash, wiped out after | Degreased by hand, non-caustic |
| Racks and runners | Removed first unless pyro-rated | Soaked in a heated dip tank |
| Between the door glass | Stays dirty, heat can discolour it | Door split where the design allows |
| Door seal area | Left alone, seals must not be scrubbed | Cleaned by hand around the gasket |
| Hob and extractor | Untouched | Add-ons at £23–28 and £28 |
| Time | 1.5–3 hours locked, plus cooling | About 90 minutes for a single |
| Cost | Around £1.30 of electricity a cycle | £77 fixed for a single oven |
Common questions
Can the racks stay in during a pyrolytic cycle?
Only if the maker rates them for it. Miele's PyroFit racks and FlexiClip runners are built to stay in; standard chrome shelving discolours and telescopic rails seize once their lubricant burns off. Bosch and Neff both tell you to empty the oven completely first.
How much electricity does a pyrolytic cycle use?
Which? measured an average of about 5kWh, around £1.30 a cycle at current rates, or roughly £16 a year if you ran it monthly. The bigger cost is time: the oven is locked for the cycle plus cooling, most of an afternoon.
Is a pyrolytic oven still worth buying?
For the cavity, yes. Ash wipes out far more easily than baked-on fat ever will. Treat the cycle as a cavity tool and pair it with an occasional hand clean of the parts it cannot reach.
Why does the oven smoke during the cycle?
Loose debris and thick fat deposits char before they turn to ash, and a heavily soiled oven can smoke enough to set off the alarm. Scrape out anything loose, mop up standing grease, put the extractor on and open a window before you start, and keep pet birds well away.