Why a bigger box costs less per litre
Every freezer has to hold a cold box against a warm room, and that job is done by two things: the insulated shell keeping heat out, and the compressor pumping out whatever heat gets through anyway. Neither one scales in step with capacity. A small freezer has proportionally more shell surface for the amount it stores, the classic surface-area-to-volume problem, so more heat leaks in per litre; its compressor and motor also tend to be a smaller, less efficient unit. A university energy-efficiency program's freezer buying guide puts the underlying mechanism plainly: “Smaller freezers have higher energy intensity… This is due to their larger surface area to volume ratio and smaller, less efficient compressors and motors.” The same physics applies whether the freezer is running a laboratory or a garage.
The government's own registration data confirms it holds for the 378 chest and upright freezers on the Australian market. Chest freezers under 150 L (101 models, median capacity 142 L) carry a median 200 kWh a year, working out to 45.6¢ per litre of capacity on NSW's rate. Chest freezers from 500 to 1,000 L (53 models, median capacity 533 L) carry a median 404 kWh a year, just 24.6¢ per litre, despite using more than double the raw electricity. Uprights show the identical pattern on a smaller scale: a ~88 L unit runs 61.1¢ per litre against a ~168 L unit's 41.7¢.
What this costs, state by state
Registry medians by size band, at each band's own median capacity. Chest and upright are different classes to begin with, so compared separately.
| State | Rate | Small chest, ~142 L | Large chest, ~533 L | Small upright, ~88 L | Large upright, ~168 L |
|---|---|---|---|---|---|
| New South Wales | 32.4¢ | $64.80 | $131 | $53.78 | $69.98 |
| Victoria | 29.8¢ | $59.60 | $120 | $49.47 | $64.37 |
| Queensland | 31.2¢ | $62.40 | $126 | $51.79 | $67.39 |
| South Australia | 38.1¢ | $76.20 | $154 | $63.25 | $82.30 |
| Western Australia | 33.6¢ | $67.20 | $136 | $55.78 | $72.58 |
| Tasmania | 28.9¢ | $57.80 | $117 | $47.97 | $62.42 |
| Australian Capital Territory | 27.4¢ | $54.80 | $111 | $45.48 | $59.18 |
| Northern Territory | 31.7¢ | $63.40 | $128 | $52.62 | $68.47 |
Reference rates for 2026–27. Your row is highlighted once you set your location.
What this means when you're actually shopping
Per litre of storage, the small chest freezer in the table above costs 1.9× what the large one does to run, and the small upright costs 1.5× what the large upright does. That has two practical consequences for the running-cost side specifically (purchase price is its own separate decision, and this data doesn't cover it the same rigorous way). First, if the actual need is a genuinely large amount of frozen storage, one big freezer beats two or three small ones covering the same total litres on the electricity bill, since each small unit pays its own small-unit running-cost premium rather than sharing one larger, better-insulated shell. Second, don't oversize out of habit: a small household buying a small freezer isn't being penalised for it in dollar terms, since the per-litre premium only matters once it's multiplied across genuinely large capacity.
Common questions
Does a bigger freezer really cost more to run?
In raw kilowatt-hours, yes. But per litre of storage, a bigger freezer of the same type is cheaper to run, not more expensive: the government registry shows a large chest freezer running at roughly half the per-litre cost of a small one, and a large upright at roughly two-thirds.
Why are small freezers less efficient per litre than big ones?
A smaller freezer has proportionally more insulated shell surface for the amount it stores, so more heat leaks in per litre, and its compressor and motor tend to be smaller and less efficient too. Both effects shrink as the freezer gets bigger, which is why the per-litre running cost falls as capacity rises.
Is it cheaper to run one big freezer or two small ones for the same total capacity?
One big freezer, generally. The per-litre running cost drops as capacity rises within a freezer type, so splitting the same total storage across two or three smaller units means paying that small-unit premium on the electricity bill more than once.
Does the same registry-digging approach turn up anything for an old spare fridge?
Yes. Our second fridge cost guide runs the identical government registration database for a 20-plus-year-old garage fridge against a dedicated bar fridge, and finds age costs more than this page's size gap does, roughly 668 kWh a year for doing the identical job.
Sources
Per-model kWh-per-year and litre capacity for the size-band comparison: the same energyrating.gov.au registration database (July 2026 snapshot) our freezer running cost calculator's own model finder uses, filtered to the 378 currently registered chest and upright models. Surface-area-to-volume and compressor-efficiency mechanism: University of Minnesota Technical Assistance Program (MnTAP), Freezer Best Management Practices (written for laboratory ultra-low freezers, but the physical principle it describes applies to any freezer type). Electricity rates: AER Default Market Offer and each state's regulated reference tariff, current for 2026–27. All fetched July 2026.