There is a moment in most kitchen projects where someone says "it would be nice to have a second oven" and someone else points out there is nowhere to put one. That is usually where the idea dies.
It shouldn't. The 45cm compact oven exists precisely for that gap — and the modern ones do considerably more than bake. This guide covers what a compact oven actually is, the difference between the types, the sizes you need to plan for, and the honest question of whether you need one at all.
What Is a Compact Oven?
A compact oven is a built-in oven roughly 45cm tall instead of the standard 60cm. The width stays the same — 60cm — so it fits standard kitchen cabinetry. It is shorter, not narrower.
That reduced height is the whole point. It fits into a compact housing aperture, which means you can stack one above a full-size oven in a single tall unit, or fit one at eye level in a kitchen where a second full oven would never work.
Capacities typically run from around 40 to 50 litres. That is smaller than a main oven's 65–75 litres, but it is a genuine oven cavity — not a microwave with a browning element. A 50-litre compact oven will take a shelf of roast potatoes, a tray of cookies, or a decent-sized chicken.
The Three Types of Compact Oven
1. Compact Oven (Solo)
A straightforward second oven in a smaller body. Fan, conventional, grill — the functions you would expect from a main oven, in a 45cm cavity. No microwave, no steam.
Best for: households that genuinely need two ovens running at once — big families, keen bakers, anyone who hosts. It is the simplest option and usually the cheapest.
2. Compact Oven with Microwave (Combi)
This is the one most people end up buying, and for good reason. It is a real fan oven with microwave functionality built in, and crucially the two can run together.
That combination mode is the feature worth understanding. A microwave alone heats food fast but leaves it pale and soft. Convection heat alone browns and crisps but takes time. Run both and you get microwave speed with oven results — a jacket potato in twenty minutes with skin that actually crackles, a lasagne reheated through the middle without a dried-out top.
Most modern combis also include an air fry function, using a perforated rack and fast fan circulation to crisp food with little or no oil. If you have a countertop air fryer, this is the appliance that makes it redundant.
Best for: most kitchens. It replaces two or three countertop appliances and gives you a second oven at the same time.
If you are weighing this against a dedicated built-in microwave, our guide to built-in microwaves — solo, grill and combi covers that comparison in detail.
3. Compact Steam Oven
Steam ovens come in two forms. Added steam (sometimes called natural steam) injects moisture into a conventional oven cycle — excellent for bread, roasting meat and reheating rice without drying it out. Full steam cooks with steam alone, which is gentler and better for fish and vegetables but won't brown anything.
Many premium compact ovens now combine steam and microwave and convection in one cavity. That is genuinely four appliances in one 45cm box.
Best for: people who cook a lot of bread, fish or vegetables, and anyone who reheats leftovers regularly and is tired of the microwave ruining them.
The Sizes You Need to Plan For
This is where compact ovens catch people out, so measure before you buy.
The housing aperture. A UK compact oven housing has an internal aperture of roughly 452mm high × 560mm wide. A standard full-size single oven aperture is roughly 590mm high × 560mm wide. The widths match; the heights do not. A compact oven will not fill a full-size aperture, and a full-size oven will not go into a compact one.
Depth. Most compact ovens need around 550mm of depth inside the housing. Standard base and tall units accommodate this, but check if you have shallow cabinetry or an awkward wall behind.
The appliance is smaller than the aperture — deliberately. An oven with external dimensions of 595 × 456 × 570mm typically needs a cut-out of 560 × 446 × 549mm. That difference is the ventilation clearance the manufacturer requires. Ovens generate serious heat and need airflow; if you box one in tightly you will shorten its life and potentially void the warranty.
Stacking in a tall unit. The classic configuration is a full-size oven at mid-height with a compact oven directly above. For that you need a tall housing unit — UK standards are 1,900mm, 2,100mm and 2,150mm high — with both apertures pre-cut. If your existing unit only has one aperture, this is joinery work, not a swap.
Our guide to integrated appliances, doors, hinges and housing sizes goes into the cabinetry side in more depth.
Electrical Supply — Check This Before You Order
Compact ovens vary enormously in what they draw. Many combi models are rated around 2,600W and are supplied with a standard 13A plug already fitted, so they plug into a normal socket behind the housing. No electrician required.
Others — particularly larger or higher-specification models — need hard-wiring to a dedicated circuit. And if you are stacking two ovens, the combined load matters: two appliances on one 13A socket via an adaptor is not acceptable.
The rule is simple. Check the product's power rating and whether a plug is fitted before you order, and make sure there is a suitable, accessible supply within reach of the housing. Sockets should be positioned in an adjacent cabinet, not directly behind the oven where heat and access are both problems.
So Do You Actually Need One?
Be honest about this, because a compact oven is not a small purchase.
A compact oven earns its place if:
- You regularly cook for more than four people, or host at Christmas and find yourself juggling trays
- Your worktop currently holds a microwave, an air fryer, or both, and you want that space back
- You have a smaller kitchen where a full second oven is impossible but a stacked compact will fit
- You reheat leftovers often and want them to come out properly rather than rubbery
- You bake — having a second cavity at a different temperature changes what is possible
You can probably skip it if:
- You cook for one or two and your main oven is rarely full
- Your microwave is used for reheating drinks and little else — a cheap countertop unit does that fine
- Budget is tight and the money would be better spent on a better main oven, or on a pyrolytic cleaning function you will use weekly
- Your kitchen has no tall unit and adding one means reworking the layout
What to Look For When Comparing Models
Cavity capacity. 50 litres is generous for a compact; 40 litres is tight. Check what shelf area you actually get, not just the headline number.
Genuine air fry, not a marketing label. A real air fry function comes with a perforated rack or basket. If the spec sheet mentions air fry but nothing is included to put the food on, it is a fan setting with a new name.
Cleaning. Steam clean softens light soiling so it wipes away and is standard on most compacts. Pyrolytic self-cleaning is rarer in compact sizes because of the insulation required — if you want it, check explicitly.
Connectivity. Wi-Fi and app control let you preheat before you get home and check timers from another room. Genuinely useful for some households, ignored entirely by others. Don't pay a premium for it unless you know you will use it.
Energy label. Compact ovens carry the same rescaled A–G label as everything else. If you are comparing a new model against an old one, read our guide to why your new appliance is only a D before you draw conclusions — the scales are not comparable.
A Quick Pre-Purchase Checklist
- Measure your housing aperture — height, width and depth
- Confirm the cut-out dimensions on the product spec match it
- Check the ventilation clearance the manufacturer requires
- Confirm the power rating and whether a 13A plug is fitted
- Locate a suitable, accessible socket or supply
- Measure your delivery route — doorways, stair turns, hallway width
- Decide which functions you will genuinely use, and stop paying past that point
The Short Version
A compact oven is a 45cm-tall built-in oven that fits a standard 560mm-wide housing. The combi versions — oven plus microwave plus air fry, often plus steam — do the work of three or four appliances in one cavity, which is why they have become the default second oven in UK kitchens.
Measure the aperture, check the power supply, and be honest about how you cook. Get those three right and it is one of the most useful appliances you can add to a kitchen.
Browse our range of built-in and compact ovens, or get in touch if you would like help checking a specific model against your cabinetry.
