Start with the food, not the equipment
- Keep the door shut
Open the fridge and freezer only when needed. Food Standards Agency and Food Standards Scotland guidance gives up to four hours for a closed fridge, and longer estimates for a freezer. Those times vary with the appliance, room temperature and door opening.
- Read a fridge thermometer
Normally aim for 5°C or below. During a power cut, both UK food authorities advise keeping chilled food below 8°C. A thermometer gives more useful evidence than elapsed time alone.
- Follow current food advice
If the fridge reaches 8°C or above, food that normally needs refrigeration should be eaten within four hours or discarded, following the relevant food authority's advice. Be especially cautious for young children, pregnant people, older people and anyone with an underlying health condition.
When backup power may be worthwhile
A power supply may help when cuts are likely to last beyond the time your fridge can hold a safe temperature, when chilled food cannot be moved safely, or when the household has a specific need for reliable refrigeration. A fridge thermometer and a plan for using perishable food are useful even without a battery.
A portable power station can run a compatible fridge without engine exhaust at the point of use, but its stored energy is finite. A fuel generator can continue while safely supplied with fuel and maintained, but it creates carbon monoxide and has strict outdoor siting and electrical requirements. A power bank intended for phones is not a fridge supply.
Check the exact fridge and backup supply
- Find the fridge's electrical details
Read its rating plate and manual. Note the supply voltage and running power or current. Ask the manufacturer about compressor starting demand if it is not documented.
- Estimate energy separately
A UK fridge energy label reports annual kWh, which can give context but cannot promise a single day's outage use. A plug-in energy meter used in normal operation can show actual Wh over a representative period. Room temperature, door opening and fridge condition can change that result.
- Match both limits
Compare the fridge's starting demand with the source's stated brief surge rating, and its running demand with the continuous AC rating. For a battery, compare measured daily Wh with usable AC energy rather than the battery's nominal Wh alone. Allow for conversion losses and uncertainty.
- Try the complete setup in advance
Follow the appliance and backup-supply manuals. Confirm that the fridge starts and stays running, that cables and plugs remain in good condition, and that the temperature stays in the safe range. Record actual energy use if the equipment provides it.
Power does not reset food safety
Food safety depends on the food's temperature and how long it was warm. Check the current Food Standards Agency or Food Standards Scotland guidance for the part of the UK where you live. If you cannot establish that perishable food was kept safely chilled, do not use the battery runtime or the fact that the fridge is cold again as a safety test.
Connect and use backup power safely
Use the fridge's normal plug only with a suitable output specified in the power station or generator manual. Keep cables and connectors dry, undamaged and within their ratings. Do not improvise a connection to a wall socket or household wiring. Any fixed backup connection needs a competent electrical professional.
A fuel generator belongs outdoors, away from doors and windows, never in a garage, shed or partly enclosed space. The UK Chief Medical Officers' published emergency script specifies at least 6 metres from the building with exhaust facing away from openings. Follow the manufacturer's instructions and current local advice. A carbon monoxide alarm is an additional safeguard, not a reason to put a generator nearer the home.
What this guide cannot tell you
Different fridges cycle differently. Starting demand, room temperature, door opening, usable battery output and inverter losses affect the result. This guide does not certify a particular battery, generator, cable or food item. Refrigerated medicines and medical equipment need an individual continuity plan from the pharmacist, supplier or care team.
Products that may help
Specific options, with the limitations visible.
These are affiliate links. The recommendation is based on suitability and evidence, not commission.
EcoFlow DELTA 3 Classic portable power station
EcoFlow DELTA 3 Classic, 1024Wh, UK model EFDELTA3C-UK-CBox-L
A rechargeable 1kWh-class power station for households that need an AC output without running a fuel generator. Check appliance demand and expected duration before buying.
- Useful for
- A household that has measured its fridge energy use and confirmed the compressor start-up demand fits the station output.
- Probably not for
- A household without appliance measurements, or anyone relying on an unverified runtime for food safety or medicine.
- 1,024Wh rated capacity is relevant to a measured fridge load.
- 1800W rated AC output is higher than compact stations.
- No engine exhaust at the point of use.
- No tested runtime for the reader’s fridge.
- AC conversion loss reduces usable energy.
- Compressor start-up demand can exceed running power.
- The station still needs recharging.
Confirm the exact fridge start-up demand and daily energy use before purchase. A power station cannot guarantee food safety during an outage; follow UK food safety advice. Do not connect it to fixed household wiring.
ETI digital fridge/freezer alarm thermometer
ETI 810-210
A remote-probe thermometer that can show current, highest and lowest fridge or freezer temperatures and sound an alarm when a set threshold is crossed.
- Useful for
- A household wanting to observe fridge or freezer air temperature without repeatedly opening the door.
- Probably not for
- Anyone expecting the reading to establish that every food item is safe after an outage.
- Remote probe allows a reading without opening the door.
- Max/min memory helps show temperature excursions.
- Programmable audible alarm.
- Measures the probe location, not the temperature inside each food item.
- Manufacturer accuracy is ±1°C.
- Requires a working AAA battery and correct alarm setup.
A reading alone cannot establish food safety after a power cut. Follow current UK food safety guidance and discard food when in doubt.