How Long Should a Refrigerator Run? Cycle Times

Short answer: A healthy full-size refrigerator should run roughly a third of the time, about eight hours across a day, delivered in cycles of roughly fifteen to forty minutes, with thirty to fifty percent covering most units across a year. A new fridge, one recovering from a power cut, or one just loaded with groceries runs near continuously for a while. Constant running signals a fault only when the box also fails to hold its setpoint.

How long should a refrigerator run? For a healthy full-size unit in an ordinary kitchen, the usual answer is roughly a third of every hour, which lands somewhere near eight hours across a day, and it arrives as a run of separate cycles rather than one long block. That is a planning figure and not a specification, because run time is not a fixed property of a machine. It is the result of the room, the setpoint, the door traffic, the state of the coils and the seal, and what went into the box that day. Two identical fridges in two different kitchens will honestly report two different answers.

These notes set out what normal looks like, in minutes per hour and in hours per day, and then give you a way to check your own fridge with nothing but a clock. They cover why a brand new fridge runs almost without stopping for a day or two, why summer legitimately adds run time, which of the fan noises people count as running when the compressor is actually off, what continuous running costs per month using the same illustrative figures as our refrigerator running-cost notes, and the short list of signals that separate a long duty cycle from an actual fault. Where that line is crossed, the diagnosis belongs in the not-cooling troubleshooter rather than here. Put your own timing figures through the cost-per-use calculator to see what your duty cycle is worth in dollars.

How long should a refrigerator run each day?

The short answer is roughly a third of the time, which is about eight hours across a full day, delivered in cycles rather than in one continuous stretch. A wider band of about thirty to fifty percent of the time covers most healthy full-size refrigerators once you allow for the difference between a cool winter kitchen and a warm summer one. Compact units, second fridges in hot spaces, and older machines routinely sit above that band without anything being wrong with them, which is why the band is a starting point rather than a verdict.

It is worth being direct about why no exact number exists. Manufacturers do not publish a duty cycle the way they publish a capacity or an annual energy figure, because run time is not a property the machine owns. It is the outcome of an energy balance: heat leaks into the box through the walls, the door seal and every opening, and the compressor runs for however long it takes to move that heat back out. Change the room, the setpoint, the load or the condition of the coils, and the same fridge honestly produces a different number.

That is also why the annual kilowatt-hour figure on the yellow label is a more portable number than any run time. The label already blends the on periods and the off periods across a whole year of standard conditions into one figure, which is the basis for the running-cost arithmetic in our refrigerator running-cost notes. Run time is the thing you can observe at home; the label is the thing you can compare between machines. Use each for what it is good at.

Duty cycle in plain terms: minutes per hour

Duty cycle is simply the share of time a machine spends running, and for a fridge the easiest unit is minutes per hour. Twenty minutes of compressor time in an hour is a duty cycle of about 33 percent, which multiplies out to roughly eight hours a day. Thirty minutes an hour is 50 percent, or twelve hours a day. Forty-five minutes an hour is 75 percent, or eighteen hours a day. Sixty minutes an hour is continuous running, and the fridge never gets a rest.

The arithmetic in both directions is worth having in your head. To convert minutes per hour into a percentage, divide by 60 and multiply by 100. To convert a percentage into hours a day, multiply by 24 and divide by 100. To convert either into an energy figure, remember that energy use rises almost in step with the duty cycle, because the compressor is what draws the power and it draws roughly the same amount whenever it runs. A fridge running twice as much uses close to twice the energy.

One caution keeps this honest. The compressor does not draw a constant figure the entire time it runs, and the fans, the control board and the automatic defrost heater all add their own smaller draws on their own schedules. So duty cycle is a very good proportional guide and a rough absolute one. It tells you reliably whether this month is worse than last month; it does not replace a label figure or a meter. The cost-per-use calculator will turn a timed duty cycle into an illustrative yearly figure for your own electricity rate.

What a normal compressor cycle sounds and feels like

Knowing what you are listening for makes the timing exercise far easier. A compressor start is usually a soft click from a relay followed by a low hum that settles within a second or two into a steady, fairly quiet drone. While it runs, you can generally feel a faint vibration if you rest a hand on the lower back or the lower side of the cabinet, and the air coming off the coils at the back or underneath is warm, because that is heat being rejected from inside the box.

A shutdown is quieter than a start. The hum fades, and a few seconds later many fridges produce a gurgling or trickling sound as refrigerant pressures equalise. That gurgle is one of the most misread noises in a kitchen, because it happens after the compressor stops rather than while it runs, and people who hear it assume the machine never rests. Occasional pops and creaks from the plastic liner expanding and contracting as the temperature swings are also normal and are unrelated to the compressor.

Cycle lengths vary more than most people expect. Somewhere between about fifteen and forty minutes of running, with a comparable or longer rest, describes a great many healthy fridges, and plenty sit outside it in both directions. The pattern matters more than the individual cycle: run, stop, rest, run again is healthy at almost any cycle length, whereas starting and stopping every few minutes is short cycling and is a genuine problem worth chasing.

Why a new fridge runs almost constantly for the first day or two

A new refrigerator arrives at room temperature and has to cool everything about itself before it can hold anything at a setpoint. The cabinet walls, the liner, the shelves, the drawers and the air inside are all warm, and the moment you load it, so is the food. Pulling all of that down from a room temperature start is the single biggest cooling job the machine will ever be asked to do, and it is entirely normal for the compressor to run close to continuously for the first day, sometimes into a second.

The same thing happens for the same reason in three other situations. After a power cut of any length, the fridge restarts against a box that has warmed up and runs hard until it recovers. After a manual defrost, or after any period with the door propped open for cleaning, the recovery run is long. And after a large grocery delivery, when a warm load lands all at once, the fridge runs extended cycles until that load reaches temperature. None of these is a fault, and all of them look identical to the fault from the outside if you only listen.

The test that separates them is time plus temperature. Leave the fridge alone for a full 24 hours with the doors mostly closed, then put a thermometer in a glass of water in the middle of the fridge compartment and read it after a few hours. If it is at or near the setpoint and the machine has begun cycling on and off, the long run was pull-down and it is finished. If the box is still warm after a couple of days of continuous running in a normal room, that is the point at which the not-cooling troubleshooter becomes the right place to look.

Normal run time by season, and why summer is longer

A refrigerator does not make cold. It moves heat from inside the box to the room, and the difficulty of that transfer depends on how warm the room is. In a cool kitchen, the coils shed heat easily and each cycle is short. In a hot kitchen, the same coils have less temperature difference to work with, the compressor has to run longer to move the same heat, and the duty cycle climbs. Nothing about the machine changed; the job got harder.

That is why the same fridge can look untroubled in February and alarming in August. Run time rising with the season is expected behaviour, and a fridge that runs a third of the time in a cool kitchen may well run half the time or more in a hot one. The practical consequence is that comparing your current run time against your memory of last winter will mislead you almost every time. Compare against the same season, or better, against a timed reading you took in a comparable week.

Two related effects amplify it. Kitchens are hot rooms by construction, and an oven, a dishwasher on a heated dry cycle, or a stovetop running for an hour will raise the air around the fridge well above the rest of the house. And humidity adds its own load, because moist air entering the box each time the door opens has to be cooled and its moisture condensed and frozen out on the evaporator, which is work the compressor pays for. A humid August day is a heavier day for the fridge than a dry one at the same temperature.

What makes a refrigerator run longer: heat, load, door use, coils, seals

Five things account for nearly all of the variation in a healthy fridge, and they are worth knowing in order because the last two are the ones you can actually fix.

Ambient heat. The temperature of the air around the machine is the largest single factor, which is why the season, the room, and the appliances beside it matter so much.

Thermal load. Warm food and drink placed into the box carry heat that has to be removed. A full grocery run, a warm pot of leftovers, or a case of room temperature drinks all buy extra run time until they reach temperature.

Door use. Every opening exchanges cold air for warm, humid room air. Frequent or lengthy openings, and a household that browses with the door open, add up over a day into meaningful extra running.

Condenser coils. The coils are how the heat gets out. When they are caked with dust, pet hair and kitchen grease they insulate instead of shedding heat, so every cycle runs longer to achieve the same result. This is the most common cause of a slow, unexplained climb in run time over a year or two, and it is fixable in twenty minutes.

Door seal. The gasket around the door hardens and deforms with age until it stops sealing at the corners or along an edge, leaking cold continuously rather than only when the door is open. A slip of paper closed in the door that pulls out with no resistance is the classic quick test.

The last two belong to maintenance rather than diagnosis, and both are covered as routine jobs in our appliance maintenance plan and, for the fridge specifically, in the refrigerator cleaning walkthrough.

Where the fridge sits: garage, sunlight, and the wall gap

Placement decides ambient heat, and ambient heat decides run time, which makes the spot a fridge stands in one of the largest variables nobody adjusts. A fridge in an unconditioned garage, outbuilding or utility space lives in whatever the weather is doing, and in a hot month that means a duty cycle far above anything a kitchen unit would show. It is the same reason the old second fridge is usually the most expensive cold box in a house, a pattern our refrigerator running-cost notes and the freezer running-cost notes both trace out in dollars.

Direct sunlight through a window onto the cabinet does the same thing on a smaller scale, as does standing immediately beside an oven, a range, a dishwasher that vents steam, or a heating vent. None of these is dramatic on its own and all of them are cumulative.

The wall gap is the placement issue people most often get wrong, because it is invisible once the fridge is in place. The condenser needs air to move across it, and if the machine is pushed hard against a wall, boxed into a tight cabinet surround, or has its top vent covered by stacked items, the warm air it rejects gets recirculated straight back through the coils. The machine then runs longer to reject the same heat, exactly as if the coils were dirty. Manufacturers specify a clearance for this reason, and it is one of the few numbers genuinely worth reading in the manual for your own model rather than taking from a general figure. If you cannot find it, giving the back and top a comfortable gap and keeping the area clear costs nothing.

Illustrative run time and what it costs per year

Because energy use rises roughly in step with duty cycle, run time converts into money with very little arithmetic. The chart below takes a modern full-size fridge that would use around 500 kilowatt-hours a year at a normal duty cycle of about a third, and scales it up through progressively longer run times to continuous running, pricing each at an illustrative 16 cents per kilowatt-hour.

Read the chart as a proportional map rather than a price list. The labels attached to each row are the usual explanations for a duty cycle of that size, not a claim that dirty coils always produce exactly 60 percent. What the chart does establish is that the difference between a fridge behaving well and a fridge running flat out is roughly a threefold difference in energy, worth something like $160 a year on these illustrative numbers, and that the intermediate cases are proportionally intermediate. Enter your own timed figures and your own rate in the cost-per-use calculator to place your machine on this scale.

An illustrative day for a healthy fridge

The second chart splits a single day rather than a year, showing where the 24 hours go on a fridge running at about a third duty cycle in a normal kitchen. It is the same machine as the top row of the chart above, viewed by the clock instead of by the bill.

The useful thing about seeing the day laid out is that the idle share is the biggest one. A fridge that genuinely never rests has lost roughly two thirds of its day, and that is why continuous running is both a diagnostic signal and a cost problem at the same time. It also shows why counting fan noise as running time distorts the picture so badly: the fans can be turning through much of that 62 percent slice, and if you count them, a normal fridge looks like a broken one.

Frost-free defrost cycles: the running you should not count

Almost every modern fridge is frost-free, which means it periodically warms a small heater near the evaporator coil to melt off the frost that would otherwise build up and choke the airflow. That cycle runs on its own schedule, lasts a matter of minutes rather than hours, and while it happens the compressor is normally off. The melted water runs down a drain channel into a shallow pan near the compressor, where the warmth of the machine evaporates it away.

Two things about defrost confuse people who are timing their fridge. The first is that it produces noises: hissing, ticking, faint sizzling as water hits a warm surface, and dripping or trickling as the water finds the drain. Those noises can easily be mistaken for the machine running hard, when in fact the compressor is resting. The second is that the interior temperature drifts up slightly during a defrost and then recovers afterward, which means a temperature reading taken at exactly the wrong moment can look like a problem that is not there.

The energy defrost uses is already inside the annual figure on the yellow label, so there is nothing to add to your arithmetic for it. What is worth knowing is that a defrost system which fails leaves frost to build on the evaporator, airflow drops, and the fridge responds by running longer and longer while cooling worse. Heavy frost or ice on the back wall of the freezer compartment, on a fridge that is supposed to be frost-free, is one of the clearer pointers toward a defrost fault rather than a heat load problem.

Temperature settings and the run time they buy

The setpoint is the one variable in this entire piece that you control directly with a dial, and it is the one most often set badly. Commonly cited targets are around 37 to 40 degrees Fahrenheit for the fridge compartment and near 0 degrees for the freezer, cold enough for safe food storage without asking the compressor for extra work. Every degree colder than needed is bought with additional run time, permanently, for no benefit to the food.

Two practical notes make the setting reliable. Many fridges have a numbered dial from one to five or one to nine rather than a temperature, and those numbers are relative positions rather than degrees, so the only way to know where you actually sit is to put a thermometer in a glass of water in the middle of the compartment and read it after several hours. And the fridge and freezer controls on many single-compressor designs are not independent: the cold is generated in the freezer section and shared to the fridge section through a damper, so turning the fridge colder can push the freezer colder too, buying run time in both.

How full the fridge is, and why an empty one runs more

The thermal mass argument is real but smaller than folklore suggests. Food, drink and anything else cold in the box holds its temperature when the compressor stops, which buffers the interior against the warm air that arrives when the door opens and smooths out the cycling. An almost empty fridge is mostly air, air holds very little heat, so opening the door dumps the cold out quickly and the compressor has to make it back.

The reverse effect matters more in practice. A fridge that is packed to the ceiling can block the internal vents through which cold air circulates, usually at the back wall and near the top. When that happens the cold stops reaching parts of the box, the thermostat sees a warmer reading than the machine is actually producing, and it calls for more cooling, so run time rises while some shelves stay warm and others freeze. Full but not jammed, with the vents clear, is the target that satisfies both effects.

Do not go out of your way to fill an empty fridge with containers of water to add mass. On a modern, well insulated unit the saving is small enough to be hard to notice, and the extra volume comes with its own handling nuisance. If you have a fridge that is genuinely mostly empty most of the time, the honest question is whether it needs to be running at all, which is the same question our refrigerator running-cost notes put to the second fridge in the garage.

Ice makers, water dispensers, and door alarms

An automatic ice maker is a small freezer within a freezer, and making ice is work. Each harvest cycle fills a mould with water at supply temperature, freezes it solid, and then usually warms the mould briefly to release the cubes, which is heat added back into the compartment on purpose. A household that empties the bin daily is asking for meaningfully more run time than one that barely touches it, and a fridge that has just had its bin emptied into a cooler will run hard for hours refilling it.

A through-door water dispenser adds a second, smaller load, because room temperature water entering the tank has to be chilled, and because the dispenser recess in the door is a weak point for both insulation and sealing on some designs. This is one of several reasons the through-door ice and water assembly gets singled out in our refrigerator lifespan notes as the most service-prone system on the machine, and it is worth weighing when you are choosing one, a decision covered in the refrigerator buying walkthrough.

Door alarms deserve a mention on the other side of the ledger. A fridge that beeps when a door has been left ajar for a minute or two is doing something genuinely useful for run time, because a door that has not quite latched is the single fastest way to turn a healthy duty cycle into a continuous one. If your fridge has the feature, leave it enabled. If it does not, a habit of glancing back at the door is worth more than most of the settings in this piece.

Run time by fridge type: top-freezer, side-by-side, French door, compact

Type changes run time less than people expect, and considerably less than age or placement do. In broad terms, a simple top-freezer design has the least door area and the fewest openings into the cold space, a side-by-side has two tall doors and often a through-door dispenser, and a French door design puts the fridge compartment at eye level behind two smaller doors with a freezer drawer below, which usually means less cold spilling out per opening than one full-height door would. Those differences are real, but they are differences in door behaviour rather than in the fundamental machine.

Compact and mini fridges are the genuine outlier, and they usually run a higher share of the time than a full-size unit. Thinner insulation, a smaller compressor, and a much smaller thermal mass inside mean the box warms faster when the door opens and cools faster when the compressor runs, so cycles tend to be shorter and more frequent. That is normal for the format, and it is why a mini fridge is only the frugal choice when it replaces a need rather than adding one.

The comparison worth avoiding is the one against a neighbour, a relative, or an internet stranger. Different types, different ages, different rooms and different setpoints make cross-fridge comparison close to meaningless. The only comparison that carries information is your own fridge against your own fridge, timed twice in comparable conditions.

The fan noises people mistake for the compressor

Most fridges have at least two fans, and both are quieter and lighter than the compressor but far more noticeable if you are listening for something. The evaporator fan sits inside, usually behind the freezer back wall, and circulates cold air through the compartments. The condenser fan sits at the bottom or the back near the compressor and pulls air across the coils to help shed heat. On many designs one or both can continue running after the compressor stops, and on some they run in a low mode much of the time.

That is why a fridge that “sounds like it never stops” so often turns out to be a fridge whose fan never stops. The distinguishing features are useful: a compressor is a lower, heavier, steadier hum you can usually feel as a vibration in the cabinet, while a fan is lighter, airier, sometimes with a faint whirr or flutter, and it starts and stops without the relay click that precedes a compressor start.

Two fan noises are worth noticing rather than dismissing. A rhythmic ticking, scraping or chirping from inside the freezer often means the evaporator fan blade is catching ice, which points at frost or a defrost problem. And a fan that has stopped altogether, on either side, will drive run time up sharply while cooling gets worse, because heat can no longer move where it needs to. If a noise changes character, that is more informative than the noise itself.

When constant running is a fault, not a duty cycle

This is the handoff point rather than a second troubleshooter, so keep it short. Three conditions together turn long running from a duty cycle into a fault: the room is ordinary rather than hot, the box is failing to hold its setpoint measured with a thermometer, and the pattern has persisted for days rather than hours with no pull-down event behind it. Any two of those without the third usually has an innocent explanation somewhere above in this piece.

If all three are true, the causes to work through are the coils, the door seal, the two fans, the defrost system and finally the sealed system and compressor, roughly in that order of likelihood and cost. That sequence is exactly what our not-cooling troubleshooter walks through cause by cause, so there is no reason to repeat it here. Start there, work cheapest cause first, and treat a sealed system diagnosis as a professional job rather than a home one.

What constant running costs you per month

Put the top and bottom rows of the earlier chart side by side in monthly terms, because a monthly figure is the one people actually feel. On the illustrative figures used throughout, a modern full-size fridge at a normal duty cycle uses around 500 kilowatt-hours a year, which is about $80 a year at 16 cents per kilowatt-hour, or a little under $7 a month. The same machine running continuously moves toward 1,500 kilowatt-hours, roughly $240 a year, near $20 a month.

The gap is therefore something like $13 a month, or about $160 a year, for a single fridge. That is not catastrophic and it is not trivial either. It is comfortably more than most of the small savings people chase on a power bill, it recurs every month until the cause is fixed, and on a second fridge in a hot garage the same gap can be larger still. Set against a twenty-minute coil cleaning or a replacement door gasket, the arithmetic favours the repair by a wide margin.

Two honest caveats. These are illustrative planning figures at a typical rate, and your own rate may be half or double the one used here, which moves every number in the same proportion. And a fridge that is running constantly because the room is hot is not wasting the money in the same sense as one running constantly because its seal has failed; the first is buying cold you are getting, the second is buying cold that is leaking away. Run your own figures through the cost-per-use calculator, and see the wider bill context in our notes on lowering an electric bill.

How to check your refrigerator run time without special tools

The whole measurement needs a clock and some patience. Pick an ordinary day, not the day of a big shop and not a day when the kitchen has been running an oven for hours. Note the time when the compressor starts, note it again when it stops, and keep doing that across a window of two to three hours. Add up the running minutes, divide by the total minutes in the window, and multiply by 100 for a duty cycle percentage. Multiply that percentage by 24 and divide by 100 for an approximate hours-per-day figure.

Identifying the compressor by hand is easier than by ear for most people. Rest a palm on the lower rear or lower side of the cabinet: a running compressor produces a faint steady vibration that a fan does not. If you can safely see the back, warm air coming off the coils means the machine is rejecting heat and therefore running. Do not count the gurgle after a shutdown, and do not count fan noise.

Two refinements are worth the trouble if you have them. A plug-in energy monitor between the fridge and the socket shows power draw rising and falling directly, which removes all the guesswork and also gives you a real kilowatt-hour figure over a week. And repeating the exercise once in a cool month and once in a warm one gives you the seasonal shape of your own machine, which is the only baseline that will tell you anything reliable next time you wonder whether it is running more than it used to. Our appliance wattage and running-cost reference covers how to read that draw once you have it.

A worked example: timing a fridge over one evening

Work one through end to end with illustrative numbers. A household times its five-year-old French door fridge on an ordinary weekday evening, across a window from 7pm to 10pm, which is 180 minutes. The compressor runs from 7:04 to 7:31, from 8:12 to 8:39, and from 9:26 to 9:54. That is 27, 27 and 28 minutes, for 82 minutes of running out of 180.

Eighty-two divided by 180 is about 46 percent, which multiplied by 24 gives roughly 11 hours a day. That sits above the healthy third but inside the wider band, and the evening window is the busiest part of the day for a kitchen fridge, with cooking heat, door traffic and leftovers all landing in it. So the honest read is not alarm; it is that the sample was taken during the heaviest hours and probably overstates the daily average.

The household repeats the timing on a Sunday morning from 9am to noon and records 58 minutes of running out of 180, about 32 percent, or roughly 8 hours a day. Averaging the two windows and leaning toward the quieter one gives a working figure near 38 percent, or about 9 hours a day. On the earlier chart that sits between the first and second rows, so an illustrative annual figure somewhere near 570 kilowatt-hours and roughly $91 a year at 16 cents. The verdict is a normal fridge in a busy kitchen, with the coils worth cleaning before next summer. Every figure here is an illustration of the method rather than a measurement of any machine.

Common mistakes when judging run time

The errors that send people looking for a fault that is not there are consistent enough to list.

• Judging in the first 24 hours. A new fridge, or one recovering from a power cut or a defrost, is supposed to run almost continuously. Give it a full day before you form an opinion.
• Judging in a heatwave. Ambient heat is the largest variable there is. A duty cycle recorded in the hottest week of the year is not comparable to one recorded in February.
• Counting the fans. The evaporator and condenser fans can run when the compressor is off. Counting them can turn a normal 33 percent into an apparent 90 percent.
• Counting the post-shutdown gurgle. Refrigerant equalising after the compressor stops is the sound of the machine resting, not working.
• Timing a single cycle. One long run after the door was open for five minutes tells you nothing. Time a window of hours.
• Comparing to somebody else’s fridge. Different age, type, room and setpoint make the comparison meaningless.
• Assuming constant running always means a fault. It only means a fault when the box is also failing to hold temperature in a normal room over days.
• Assuming it never means a fault. The opposite error costs more, because a failing seal or choked coils quietly bills you every month until it is fixed.

When long run times mean the fridge is near the end

A duty cycle that has crept upward across years, rather than jumped in a week, is one of the more reliable ageing signals a refrigerator gives. Insulation degrades slowly, seals harden, the compressor loses some of its efficiency, and the machine compensates by running more of each hour to hold the same box at the same temperature. The fridge still works, the food is still cold, and the electricity bill is quietly absorbing the difference.

That is why rising run time belongs in the repair-or-replace conversation rather than only in the fault-finding one. The lifespan side of that decision, which types tend to last longest, which parts fail first, and how to weigh a repair quote against a replacement, is set out in our refrigerator lifespan notes, and the energy side is in the running-cost notes. A fridge running near continuously in a normal room, with no fixable cause, is usually near the end of the range where repair makes sense.

The one case where the arithmetic is unambiguous is the old second fridge. A lightly used unit in a hot garage combines the worst duty cycle in the house with the least usefulness, and unplugging it costs nothing and saves its entire share. If you genuinely need the second cold box, the choice between repairing an old one and replacing it with an efficient one is worth running through the energy-efficient appliance notes before you spend anything.

A short checklist for judging your own fridge

Run this in order and most run time questions answer themselves before you get to the bottom.

• Rule out pull-down. Has the fridge been installed, unplugged, defrosted, or heavily loaded in the last day or two? If so, wait and retest.
• Check the room. What is the air temperature around the machine, and is it beside an oven, a vent, or a sunny window?
• Measure the inside. Thermometer in a glass of water, mid compartment, read after several hours. Compare against the setpoint, not against the dial number.
• Time a window. Two to three hours, ordinary day, compressor only, and convert to a percentage and to hours per day.
• Look at the seal. Close the door on a slip of paper at several points around the frame and check the resistance when you pull it.
• Look at the coils. Dust, pet hair and grease on the coils at the back or underneath, and a clear gap behind and above the cabinet.
• Listen for the fans. Both running, neither ticking or scraping, and neither silent when the compressor is on.
• Check the freezer wall. Heavy frost on a frost-free unit points at defrost rather than at heat load.
• Convert to money. Put the duty cycle and your rate into the calculator and see what the difference is worth per month before deciding what to do about it.

Questions worth answering before you call for service

If the checklist has not settled it, a service call is reasonable, and it goes better when you arrive with observations rather than impressions. Have the answers to these ready.

How long has it been running like this, in days rather than in feelings? What is the actual interior temperature, measured, in both compartments? What is the room temperature around the machine? What is the duty cycle you timed, and over what window? Has anything changed recently, meaning a move, a power cut, a new setting, a big load, or a cleaning? Is there frost anywhere it should not be? Do both fans run? When were the coils last cleaned, and does the door seal pass the paper test?

Those answers do two useful things. They rule out the innocent explanations before anyone is paid to rule them out, and they let the technician arrive with a shorter list of likely parts. A fridge that is cold, cycling, and merely working harder than it used to is usually a maintenance job. A fridge that is warm and running continuously in a normal room is a repair job, and the difference between those two sentences is worth establishing before the visit rather than during it.

The bottom line

How long should a refrigerator run comes down to a range rather than a number: roughly a third of every hour for a healthy full-size unit in an ordinary kitchen, near eight hours a day, delivered in cycles of tens of minutes, with thirty to fifty percent covering most machines across a year. Longer than that is not automatically wrong, because ambient heat, a fresh load, door traffic, a low setpoint, dusty coils and a tired seal all buy extra run time honestly. A brand new fridge, a fridge after a power cut and a fridge that just took a full shop are all supposed to run close to continuously for a while.

The line that matters is temperature, not noise. If the box holds its setpoint and the machine cycles on and off, a long duty cycle is a cost question, and on illustrative figures the gap between a normal cycle and a constant one is around $13 a month for one fridge. If the box is warm, the room is ordinary, and the running has gone on for days, it is a fault, and the cheapest causes come first. Time your own fridge for a couple of hours on an ordinary day, write the number down, and repeat it in a different season. That single habit turns every future version of this question from a worry into a comparison.

A note on scope: these notes describe how refrigerator duty cycles generally behave and how to time your own, and they are written from published operating principles and running-cost arithmetic rather than from any machine we bought, tested, or took apart. Every run time, percentage, kilowatt-hour figure and dollar amount above, including both charts and the worked example, is an illustrative planning number at a typical electricity rate, not a measurement of your fridge, your room, or any specific model. Manufacturers do not publish a duty cycle specification, and normal run time varies widely with the room, the setpoint, the load and the design, so treat every range here as a starting point and your own timed readings as the real evidence. Consult the manual for your own model for clearances, setpoints and defrost behaviour. Refrigerant, sealed system and electrical repairs should be carried out by a qualified appliance technician, and opening a sealed system is not a home job.