A cellar man I have known for years keeps a paper thermometer taped to the wall by the stillage, and he trusts it more than any controller in the building. He is right to. The number on the front of the cooler tells you what the air is doing eighteen inches from the evaporator. The thermometer by the casks tells you what the beer is doing, and those are frequently not the same number.
Cellar temperature is the one variable in a pub that quietly decides whether the cask you paid for gets sold or poured away. It is worth knowing what the target actually is, and worth understanding the handful of things that push a cellar off it.
What temperature should a beer cellar be?
A beer cellar should hold between 11 and 13°C for cask ale. Cask Marque states that "the recommended dispense temperature of the majority of brewers is between 11 – 13°C", and that it "audits to a required range of 10-14°C allowing a little leeway".
That leeway matters, because it tells you what the tolerance really is. Two degrees either side of twelve is the working band. A cellar sitting at 15°C is not slightly warm, it is outside the audited range.
| Product | Dispense temperature |
|---|---|
| Cask ale | 11 to 13°C |
| Standard lager and keg products | 5 to 8°C |
| Extra cold products | 0 to 5°C |
| Bottled beers | 4 to 6°C |
Source: Cask Marque.
The important point in that table is that only the first row is the cellar's job. Keg and lager get to their dispense temperature through the python and the remote cooler, not by chilling the entire room down to five degrees. If somebody has dropped the cellar setpoint to make the lager colder, they have made the cask worse and not made the lager better.
Why the range is so narrow
Cask ale is a live product. It is still conditioning in the container, and the yeast that does that work is temperature dependent. Push a cellar warm and secondary fermentation accelerates, the beer throws haze, the head goes, and shelf life after venting collapses from days to hours. Pull it cold and conditioning stalls, the beer goes flat and dull, and the aromatics that the brewer built into it never arrive in the glass.
Neither failure announces itself. The beer does not spoil dramatically, it just stops being good, and the first hard evidence is usually the ullage figure at the end of the month. That is the frustrating part of this. By the time a temperature problem shows up in the numbers, you have already poured away several weeks of stock.
The seven things that push a cellar off temperature
1. Summer ambient, working on the condenser
The most common cause by a distance. The outdoor half of the system rejects heat into the air around it. If that air is already hot, or if the unit is sitting in a bin store or a narrow yard where it recirculates its own discharge, capacity drops exactly when demand peaks. This is why cellar problems cluster in July and August and vanish in October, which makes them easy to dismiss as a one-off three years running.
2. The delivery
A drop arrives at whatever temperature the lorry was. Casks and kegs land warm, and pulling them down to 12°C is a genuine heat load that lasts hours. A cellar that recovers by opening time is fine. A cellar that is still catching up when the next drop arrives was never sized for the trade the site now does.
3. Door and hatch discipline
A pavement hatch propped open through a delivery, a cellar door wedged because someone is carrying crates, an internal door to a warm corridor left on the latch. Each one is a slow leak of cold air, and unlike a mechanical fault it does not show on any diagnostic. It shows as a cooler that runs constantly.
4. A fouled condenser coil
Dust, pollen, cooking grease if the unit sits near a kitchen extract. A blocked coil cannot reject heat, head pressure rises, and the system loses capacity progressively over months. Nobody notices, because the decline is gradual and the unit simply runs for longer each week. Cleaning it properly is the single highest-value thing on a service visit.
5. Slow refrigerant loss
Systems do not usually fail by dumping their charge. They weep. Capacity falls off by degrees, the cooler runs longer, and it holds temperature right up until the first genuinely hot week, when it cannot. An engineer checking superheat and subcooling catches this months before it becomes a breakdown. An engineer who looks at the unit and ticks a box does not.
6. Stratification and a badly placed sensor
Cold air falls, warm air sits at the ceiling, and a long narrow cellar can run several degrees warmer at the far end than it does at the evaporator. If the control sensor is sitting in the cold discharge stream, the system satisfies early and the casks at the back never see 12°C. We have measured six degrees of difference across one cellar where the controller was reading a perfectly comfortable eleven.
7. Heat sources that moved in
Cellars accumulate things. An ice machine relocated downstairs because it was in the way, a glycol pack, a plate chiller, cellar lights on a switch nobody turns off, a kitchen fridge condenser venting through a shared wall. Every one of them is a heat load the original calculation never included.
Is it the cellar or the dispense?
Worth settling before anybody calls an engineer, because the two get confused constantly.
- Beer is warm and the cellar reads warm. Cooling problem. That is a cellar cooling fault or a sizing issue.
- Cellar reads correct but the first pint is warm and the second is fine. Dispense problem. The line has been standing, and that is python, remote cooler or recirculation, not the cellar cooler.
- Cask is warm, keg is fine. Cellar problem, because keg is being cooled downstream and cask is not.
- Everything reads correct and the beer is still wrong. Measure again, in the right place. See below.
Measuring it so the number means something
Three rules, and they cost nothing.
Do not trust the controller display. It reports its own sensor, in one location, and that location was chosen by whoever installed it. Use an independent thermometer.
Measure at the beer, not at the air. A thermometer by the stillage at cask height tells you something useful. One on the wall by the door tells you about the door.
Log it, do not spot check it. A reading at ten in the morning proves nothing about four o'clock on the hottest Saturday of the year, which is precisely when the system is under pressure and the cellar is being opened every twenty minutes. A cheap logger left in place for a fortnight will tell you more than a year of manual readings. The argument is exactly the same one that applies to cold room temperature logging, and for the same reason: continuous data catches the excursion, spot readings catch the average.
If you are running several sites, logging is also the only way to find out which cellars are genuinely marginal and which ones just have a vocal manager. That distinction is where the avoidable call-outs are hiding.
What a properly working cellar looks like
Quiet, is the honest answer. A cellar cooling system that has been sized correctly, sited so the condenser can breathe, and serviced by somebody who cleans the coil and checks the gas, is a piece of equipment you stop thinking about. It cycles, it recovers after the drop within a few hours, and the thermometer by the stillage reads twelve whether you look at it in February or August.
Getting there is a servicing question as much as an equipment one, and it is the argument for putting cellars on a refrigeration maintenance plan rather than calling somebody when the beer goes cloudy.
There is a real satisfaction in that. The sites that never call us are not the ones with the newest equipment, they are the ones where somebody got the specification right and then left it alone. How that specification is put together is covered in our guide to specifying cellar cooling systems.
Frequently asked questions
What is the ideal beer cellar temperature?
11 to 13°C for cask ale. Cask Marque audits against a wider 10 to 14°C band to allow a little tolerance, but 11 to 13°C is what the majority of brewers recommend for dispense.
Why is my pub cellar too warm in summer?
Almost always the condenser. Either it is fouled with dust and grease, or it is sited somewhere it cannot reject heat properly and is recirculating its own warm discharge air. Both problems only reveal themselves when the ambient temperature climbs.
Can a cellar be too cold?
Yes. Below about 10°C cask conditioning stalls, the beer loses liveliness, and the flavour and aroma the brewer intended never fully develop. Dropping the cellar setpoint to try to make lager colder is a common mistake that damages the cask and does very little for the keg.
How quickly should a cellar recover after a delivery?
A correctly sized system should be back at setpoint within a few hours. If your cellar is still recovering the following day, the system is undersized for your current delivery pattern, which is a specification problem rather than a fault.
Does cellar temperature affect how much beer I throw away?
Directly. Cask ale held above the recommended range conditions too fast, hazes, and its shelf life after venting shortens considerably. Ullage figures are often the first place a slow cellar cooling problem becomes visible, well before anyone reports a fault.
How often should a cellar cooler be serviced?
At least annually, and realistically before summer rather than after it. The visit should include a proper condenser clean and a refrigerant performance check, not a visual inspection. A service that does not touch the coil is not worth booking.
If the same cellars keep drifting
One cellar running warm in August is a maintenance job. The same three cellars running warm every August is a specification problem that maintenance will never fix, and every year you spend on call-outs is a year you do not spend on the actual cause.
If you look after cellars across several sites and you already know which ones are going to be trouble next summer, talk to us about cellar cooling before the weather does it for you. We will tell you honestly which ones need plant and which ones need a coil clean and a sensor moved.
About the author: Ali Elm runs Be Cool Refrigeration & Air Conditioning, a family-run London firm that has been installing, servicing and repairing commercial refrigeration and air conditioning since 2004. His F-Gas certified team has delivered more than 2,000 projects across London and the South East.
Last updated: 19 August 2026
Written by
Ali Elm
Ali is the Head of Operations at Be Cool Refrigeration with over a decade of hands-on experience in HVAC and commercial refrigeration. He oversees every installation, repair, and maintenance project, making sure the work meets the highest standards. Ali holds full F-Gas certification and has worked across residential, commercial, and industrial refrigeration systems throughout London and the South East. When he is not on site, he writes these guides to help business owners and homeowners understand their cooling systems better.