The power-cut food maths: what a closed fridge really buys you, and the throw-out list

The fridge is the only appliance in the house whose performance you can measure in hours of standing cold, and most households spend that budget blind - opening the door to check, moving the chicken, "just taking the ice out" - then trust the nose when the power returns. The maths of this is settled, published, and simple: a closed fridge is a cooler box you already own, and the rules below stretch its hours, spend them on the right food, and tell you with a straight face what to throw out without tasting anything.

The published line, and what it actually means

Food-safety agencies converge on the same figures, and the desk quotes them with their honest unit: a closed refrigerator holds food on the safe side of cold for around four hours through an outage, a half-full freezer for about a day, a packed freezer near two - the unit being a morning's market run and a weekend, not a number to gamble past. The temperature doing the maths is four degrees: above it the bacterial clock starts, and the food's own temperature is the meter, which is why the whole strategy is one sentence - keep the door as the one asset that cannot be bought back after it is spent.

The habits that stretch the hours

• One open, one list: write what the next meal needs while the power is still a rumor you hope against; every extra door-open trades minutes of cold for curiosity. A torch aimed at the fridge shelf is the entire product this habit needs.
• Jugs of water do the heavy lifting: water holds cold better than air; keep filled jugs on the fridge shelves and in the freezer's empty corners - frozen bottles become both thermal mass and the next day's cold water, and a packed freezer outruns an expensive one with one carton in it.
• Cluster the frozen block: grouped food shares its cold mass and thaws slower than the same food scattered - move the meat, fish and ready-food into one corner of the freezer compartment, together, the way a market woman keeps ice among the fish and not beside it.
• Cool packs ride on top: cold sinks; frozen bottles or packs on the top shelf bank a real few degrees across the whole cabinet - the freezer's own trickle to the fridge below becomes this page's upgrade.

When power returns: the decision list, not the nose

Smell is a test for spoilage organisms, not the pathogenic ones, which are odourless, tasteless and entirely capable of being the reason a household spends two nights on the toilet. So the four-hour line decides, and the desk's list is blunt: leftovers, cooked food, dairy, cut fruit and soft cheeses that rode out a warm fridge go in the bin without ceremony; raw meat and poultry that lost its chill for hours go too - the money saved is a bet with a named price. The freezer's mercy clause is published and real: food that still holds ice crystals, or reads as fridge-cold, can be cooked at once or refrozen without gamble - crystals or four degrees is the whole verdict, and it is the agencies' own rule.

The generator arithmetic this page is really for

If your outages come with a plan - a gen run twice a day, an inverter with the fridge on it - the strategy changes only in confidence: brief, scheduled power is the long outage that never happens, so the fridge goes on the circuit worth its fuel before the lights do (the load-maths already on this desk's power pages), and the door discipline still saves the fuel. If there is no plan, the closed-door budget is the plan, and this page's list is what to eat before hour four and what to surrender after it.

The desk's standing rule

Four hours is the fridge's honest word; a packed freezer doubles and doubles it again; ice crystals are mercy, a warm kitchen counter is not; and the sniff test is banned from this household's protocol by this sentence - the nose has never once detected the germ that matters, and the bin is the cheapest insurance the outage ever sold.