In this article
A generator costs a few thousand euro. Knowing whether you need one costs twenty minutes of arithmetic — and most kitchens that buy one didn't need it.
Sometime this winter, the power goes out on your kitchen. Maybe twenty minutes, maybe half a day. The question that actually matters in that moment isn't "how bad is this" — it's "how much time do I have before it gets serious" — and that answer is already fixed, sitting in the fridge and the freezer you loaded up this morning.
Most owners decide on a generator by feeling: one miserable night without power, and a quote lands in the inbox the next morning. That's the same mistake as buying insurance after the fire — the answer already exists, you just have to work it out before it matters.
This article does that arithmetic. Not a rule of thumb that fits everywhere and nowhere, but the two clocks that already govern your food safety, what renting costs against buying, and the insurance clause most policies quietly exclude.
By the end, you'll know whether your kitchen belongs in the "rent one for the rare occasion" camp, or the camp where a generator pays for itself within a few years.
Why this article exists
Search "restaurant power outage" and you'll find three kinds of answers: an insurance broker who wants a claim, a generator dealer who wants to sell a generator, and a government page with a rule of thumb written for a home fridge, not a full walk-in. Nobody puts the numbers that actually decide the question side by side.
The "four-hour" fridge rule is well known enough to feel like a cliché, but almost nobody knows the second number — how long a freezer holds — or that the two numbers together decide whether a generator is solving a problem you don't actually have.
And almost nobody has read their own policy for the clause that changes this whole decision: most property policies cover a walk-in that fails because of a fault in your own equipment, but exclude a power cut that starts at the utility — a street away — by default.
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Seven numbers, in the order they actually decide the question: first how long your stock survives, then how predictable your local grid is, then what backup power costs, and only then the buy-or-not decision itself.
1. 4 hours — your fridge's clock
Once the power cuts and the door stays shut, a refrigerator holds a safe temperature for roughly four hours. That isn't a manufacturer's rule of thumb — it follows the same food-safety logic used across the industry: above 5°C, the bacteria that cause food poisoning start doubling roughly every twenty minutes, and four hours without cooling is where that threshold is crossed. Smelling or tasting won't tell you — food that has become unsafe often still looks and smells completely normal.
Which means the first question in any outage isn't "do I need a generator" — it's "how long is this likely to last". Most power cuts run under an hour. Inside that four-hour window, an outage costs you, doors closed, literally nothing: no stock, no obligation to throw anything out.
2. 24 to 48 hours — your freezer's grace period
A freezer is more forgiving, but the number depends on something you control: how full it is. A full freezer holds a safe temperature for about 48 hours with the door shut, because the frozen mass keeps itself cold. A freezer that's only half full drops to about 24 hours — the air between packages warms up faster than the food itself.
That makes keeping the freezer full the cheapest backup power there is: a freezer you top up systematically instead of letting run down buys you a whole extra day of grace during an outage, for zero euro of equipment.
Green is safe, red is discard. The dot marks where the worked example below — a 6-hour outage — lands on each clock.
After 4 hours without power, perishables — meat, fish, dairy, leftovers — must go, even if they still look fine.
A full freezer holds for 48 hours; half-full only 24. As long as the door stays shut, only the hour count matters.
In the worked example below, the fridge has already crossed its limit but the freezer is still well inside its own — which is why the example further down only loses fridge stock.
3. 9 to 370+ minutes a year — what your own grid already tells you
Before you weigh up a generator, your own grid operator has probably already answered part of the question. European energy regulators publish, every year, how many minutes an average connection spends without power — the SAIDI index. Germany, with one of the most reliable grids in Europe, logged 11.7 minutes for 2024. Broader European reporting (CEER) shows a spread of roughly 9 to well over 370 minutes a year, depending on the country and the year measured.
That's a roughly 40-fold gap between Europe's most and least reliable grids — and the figure for your own country is published, free, by your national energy regulator. A kitchen in a region logging a few hundred outage-minutes a year is making a completely different decision than one logging under fifteen.
4. 15 to 30 kW — what actually needs power
Most generator quotes are sized for the whole building: heating, air conditioning, lighting, every piece of kitchen equipment. For an independent kitchen, that's overkill. What actually matters during an outage is the walk-in, the freezer, a handful of sockets and the POS — usually somewhere between 15 and 30 kW, not the 50 kW-plus a whole-building system asks for.
That difference decides not just the price of the generator, but whether it even fits in your storeroom: a compact set that keeps just the cooling and the essentials running is a different piece of equipment from one sized to replace the whole building.
5. What backup power actually costs — renting or buying
Renting a generator for one evening typically runs €80 to €200 a day for a set large enough to run a walk-in plus the essentials, before fuel and a deposit. Buying a 10–15 kW set outright usually costs somewhere between €2,000 and €6,000 for the unit itself; an electrician wiring it in permanently with an automatic transfer switch adds another €1,500 to €3,000 on top.
Which is why the real question is never "generator, yes or no" — it's "how often, and for how long", and that number decides the rest of this article.
6. The insurance clause nobody reads
Most property and business-interruption policies cover damage from fire, storm, or a fault in your own cooling equipment — often behind a separate "equipment breakdown" endorsement you have to add on purpose. What most standard policies do NOT cover is a power cut that originates off your premises: a fault at the utility, a cable that fails a street away. That exclusion isn't there to mislead you — it's simply the default, unless you specifically add a "utility services interruption" clause.
So don't ask your broker "am I covered for a power outage" — ask "does my policy cover an outage that starts off my premises". That's a different conversation, and it costs nothing to have before you need the answer.
Five causes of a disrupted service, and what a standard policy does with each.
The last row is the clause most owners never read — and the reason "I'm insured" and "I'm insured against THIS outage" are two different sentences.
7. The break-even — renting against buying
Everything above collapses into one simple comparison: what a generator costs to own, against what renting one for every outage would cost. Rent every time, and you only pay for the occasions you actually need it. Buy one, and you pay once, regardless of how often it turns out to be needed.
The break-even is simple to work out: divide the purchase price by what you'd spend renting each year at your own outage pattern. Land under about five years — roughly a generator's useful life before major service is due — and buying pays for itself. Land above it, and renting for the rare occasion costs less than a purchase that mostly sits idle in storage.
Run the numbers for your kitchen
Enter the value of your stock, how often you realistically lose power, and what renting or buying costs where you are. The slider shows what an outage of that length costs you — and for most kitchens, up to four hours, that answer is simply zero.
The numbers below are a realistic starting point for an independent kitchen; change them to match your own.
Rent or buy: run the numbers
Enter your own figures. The slider shows what an outage of that length costs you — for most kitchens, up to 4 hours, that's simply nothing.
—
Read these separately: the first tile is about food safety, the last two about money. A kitchen that rarely loses stock might still find a generator worth it to avoid missing a night of service.
Notice the break-even says nothing about food safety — that's the previous calculation. It's purely a money question: which is cheaper over several years, renting or buying.
A kitchen that rarely loses power but is reliably full on a Saturday night might still find a generator worth it — not to save stock, but to avoid cancelling a night of service. That's a different, legitimate reason to buy, and this number doesn't rule it out.
Your action plan
Three steps, from today to before the next storm season.
Today
- Call your broker and ask, literally: "Does my policy cover a power outage that starts off my premises?" Write down the answer.
- Work out roughly what your freezer and walk-in stock are worth on an average day.
- Look up your own country's SAIDI figure from your national energy regulator.
This month
- Plug your own numbers into the calculator above and see whether renting or buying wins.
- If renting wins: save the number of a local rental firm — you don't need to buy anything, just know who to call.
- If buying wins: get two quotes for a 15–30 kW set, not for the whole building.
Before the next storm season
- Keep the freezer systematically topped up instead of letting it run half-empty — the cheapest extra hour of grace there is.
- Tape a note by the walk-in with the time the power went out, so nobody has to guess how much time is left mid-outage.
The short answer
Most independent kitchens don't need a generator — they need a freezer that stays full and a policy with the right clause. Both cost nothing.
The kitchens that do need one are the ones where outages run more often than the national average, or where one cancelled night of service costs more than a year of rentals.
The difference between those two groups was never a feeling — it's seven numbers, and now you have all of them.