Is a second-hand iMac still a sensible buy?
An iMac is one of the few computers that holds up well on the used market. The screen is the expensive part, Apple kept the same basic shape for years, and a desktop that has sat on one desk has usually led an easier life than a laptop that has been in and out of bags. If you want a big, sharp display for study, admin, photos or working from home, a refurbished iMac often makes more sense than a laptop you would leave plugged in anyway.
The catch is that the name covers machines that are very different inside. Two iMacs can look identical from the front and be years apart in speed, and the slowest configuration Apple ever sold is also a common one second-hand. This guide walks through the three sizes, the Intel to Apple silicon switch, the storage trap to avoid, and what to check before you pay.
What is the difference between the 21.5-inch, 27-inch and 24-inch iMac?
Three screen sizes cover almost everything you will see listed in New Zealand.
- 21.5-inch (replaced by the 24-inch in 2021). The small Intel iMac came in two very different versions: a 4K Retina model, and a cheaper non-Retina model with an ordinary 1080p display. The non-Retina version usually shipped with a spinning hard drive, and it is the one to be most careful about. If the listing does not say Retina or 4K, assume it is the basic one and ask.
- 27-inch (sold until 2022). The big Intel iMac, always with a 5K Retina display. It is the only iMac where you can add memory yourself, it has the most ports, and the 2020 version was the last new Intel Mac Apple released. For anyone who wants screen space, this is the sweet spot of the used market.
- 24-inch (2021 onwards). The thin, colourful Apple silicon iMac that replaced the 21.5-inch. It has a 4.5K display, a far better camera and speakers than the 2017 and 2019 Intel machines, and it runs cool and silent. It also drops the USB-A ports and the SD card slot, and nothing inside it can be upgraded later.
There is no 27-inch Apple silicon iMac. If you need that much screen on an Apple chip, the route is a Mac mini or Mac Studio with a separate display, which is a different budget and a different conversation.
Which iMac year should you buy: Intel or Apple silicon?
The year tells you which of two eras you are buying into, and the dividing line is 2021.
Intel iMacs (2017, 2019 and 2020) are the models you will see most often. The 2017 machines use seventh-generation Intel processors, 2019 moved to eighth and ninth-generation chips with up to eight cores on the 27-inch, and the 2020 27-inch brought tenth-generation processors, solid-state storage on every configuration and a proper 1080p webcam. For email, documents, browsing, video calls and photo libraries, any of these with an SSD is still a comfortable machine. Where they fall behind is fan noise under load, power draw, and how many more macOS releases they have ahead of them.
Apple silicon iMacs (2021 onwards) start with the M1 and have since moved through M3 and M4. The jump from Intel to M1 is the same one we describe for laptops in our guide to which MacBook year to buy: much faster for everyday work, no fan noise, and a much longer runway for software updates. Older Intel-only apps run through a translation layer called Rosetta 2, and almost everything mainstream now runs natively. The trade-off is that Apple silicon Macs cannot boot Windows directly through Boot Camp.
A practical rule: if your budget stretches to a 24-inch M1, buy it and stop thinking about processors. If it does not, a 2019 or 2020 27-inch with an SSD gives you more screen for the money and will still feel quick. Only go older than 2017 if the price reflects it and you know exactly what you are getting.
Apple publishes which Macs each macOS release supports, so check your target year on apple.com before you buy rather than relying on a rule of thumb.
Why does the storage type matter more than the processor?
This is the single most important question to ask about an Intel iMac, and most listings do not answer it.
From 2012 until 2020 Apple sold many iMacs with a Fusion Drive: a conventional spinning hard drive paired with a small amount of flash storage that the system uses as a cache. On the standard 2017 and 2019 configurations that flash portion was tiny. Once it fills, the machine behaves like a hard-drive computer, which on a modern macOS means long boot times, a spinning beachball when you open apps, and a general sense that a perfectly good processor is being held back. The basic 21.5-inch non-Retina model was worse again, with a plain hard drive and no flash at all.
An Intel iMac with a genuine SSD is a completely different experience, and a 2017 model with an SSD will feel faster day to day than a 2019 model with a Fusion Drive. Every 2020 27-inch has an SSD as standard, which is one reason that year is worth paying more for. Every Apple silicon iMac has fast internal flash storage, so the question disappears from 2021 onwards.
How to check: open the Apple menu, choose About This Mac, then Storage. It will say Flash Storage, Fusion Drive or Hard Disk. If you are buying from photos alone, ask the seller to send that screen.
Can you upgrade the memory in a used iMac?
Only on one of the three sizes.
The 27-inch Intel iMac has a small door behind the stand hinge with four memory slots, and adding memory takes a few minutes with no tools. That makes a low-memory 27-inch a reasonable buy, because you can fix it yourself for little money. The 21.5-inch Intel iMac has no door; its memory sits inside the sealed case behind the glued-on display, so treat it as fixed. The 24-inch Apple silicon iMac has unified memory built into the chip and cannot be changed at all.
Storage is the same story on every size: none of these machines has storage a buyer can swap, and an external drive is the practical answer if you run out. So on a 21.5-inch or a 24-inch, buy the memory and storage you will actually need, because the configuration you buy is the one you keep.
How do you check which iMac a listing is actually selling?
Sellers often list an iMac by screen size alone, which hides the year, the processor and the storage type. Two checks sort it out.
If the machine is switched on, open the Apple menu and choose About This Mac. The first line reads something like iMac (Retina 5K, 27-inch, 2019), and the same window shows the processor, the memory and the storage. If you only have the machine in front of you, tip the stand over: the model number, a capital A followed by four digits, is printed on the underside of the foot. Apple's identify your iMac model page maps that number to the exact year and configuration.
Once you know the exact model, compare like with like. See current prices on the model pages in our refurbished iMac and desktop range, and if a laptop would suit you better after all, the MacBook collection and the wider laptop range are the places to compare.
What should you check before paying for a second-hand iMac?
- The display. Look at a plain white screen and then a plain black one for dead pixels, bright patches and faint ghost images. On older 27-inch models check the lower corners especially.
- Fan noise. Open a few heavy browser tabs and listen. A loud fan on a machine that is otherwise idle can mean dust or a tired fan, both fixable, but worth knowing before you agree a price.
- Ports and camera. Try every port and run a quick video call. Intel iMacs have four USB-A ports, two Thunderbolt 3 ports, an SD card slot and Ethernet; the 24-inch has two or four USB-C ports depending on the configuration, with Ethernet built into the power brick on the higher models.
- Account locks. The machine must be signed out of iCloud and erased, with Find My turned off. On the 2020 27-inch and every Apple silicon iMac, Activation Lock applies just as it does on an iPhone, and a locked Mac cannot be set up by the next owner.
- What is in the box. A used iMac without its original keyboard and mouse is common. Any Bluetooth keyboard and mouse will pair, but budget for them if they are missing, and make sure the power cable is included.
Every iMac we list is tested and graded in Auckland, the cosmetic grade is described against our condition guide, and each one comes with a 12-month warranty, 15-day returns and free NZ-wide delivery. If an older Mac is what you are replacing, you can put it against the new one through trade-in.
