Apple has updated its iMac range, and, as with the Late 2012 iMacs, RAM is doubled from 4GB to 8GB of memory compared to older iMacs. While 8GB should be fine for most it’s not expensive to increase the iMac’s RAM to 24GB or 32GB. See: Apple iMac (Late 2012) review (21.5- and 27-inch) and Apple launches new Haswell iMacs [Updated: September 24, 2013: new 2013 iMacs. Updated November 19, 2013: steep memory price rises. ]

If you want to speed boost that comes with extra memory please read on. Do not go the expensive route of buying the extra RAM from Apple, except for the 21-inch model. You can add third-party RAM to the 27-inch iMac for a fraction of the price Apple wants to charge you. Sadly you can't add your own RAM to the 21-inch iMac – there you're stuck with Apple's base 8GB or expensive options above.

Installing extra RAM memory in the new 21.5-inch iMac is not easy – indeed for most mortals it’s impossible. You basically need to take the iMac part to get to the memory slots, and you can’t do it with a simple screwdriver. If you want more RAM you’ll need to order this at the time you buy the 21.5-inch iMac – an extra 8GB to take the iMac to 16GB will cost you £160.

Installing more RAM memory in the new 27-inch iMac (Late 2012 and mid 2013 models), however, is simple, and you don’t even need a screwdriver. And it costs a lot less than Apple charges. Update: with rising RAM prices the gap is now reduced somewhat, but it's still cheaper to buy outside of Apple, and, as we'll explain, you get 24GB of RAM not 16GB.

Apple offers you the chance to increase RAM on the new iMacs when you order one. 16GB costs an extra £160 ($200 in the US). 32GB costs a whopping £480 (US$600) from Apple.

Apple extra RAM memory costs high iMac

Don’t waste your money buying extra RAM from Apple. You'll get more memory for a fraction of that price by buying from a third-party supplier. See: Desktop Mac reviews

We purchased two compatible 8GB RAM chips (DIMMs) from Crucial, costing us a mere £65.59 (including VAT; £52.99 ex. VAT).By November 2013, however, Crucial was charging £117.59 (inc. VAT; £97.99 without VAT) owing to the rising price of memory.

There are other companies that sell memory for PCs and Macs. What we like about Crucial is its System Scanner that you download and it checks your computer to see exactly what memory is compatible with it.

(In the US these two 8GB Dimms will set you back $86 for the pair. Update: this has now in NOvember 2013 risen to $158, so watch the prices vs Apple's carefully.)

Within 5 minutes we installed that RAM alongside the standard shipping two 4GB DIMMs – giving us a total of 24GB of memory in our 27in iMac for £65 (in November 2013 this cost had risen to £117) instead of 16GB for £160 ($200) from Apple.

If you want the maximum iMac memory you need to buy four 8GB DIMMs – compared to Apple’s £480 ($600) price tag. And you could use the two Apple 4GB DIMMs you removed to add to another iMac to boost that to 16GB for free!

How easy is it to upgrade the RAM memory in a new iMac? Really easy. Here’s how.

How to: Install extra RAM in a 27-inch iMac

First buy the extra RAM, as described above to save money on Apple's exorbitant prices.

New iMac memory from Crucial

Turn off and unplug your 27-inch iMac (Late 2012 model).

Place it flat screen down on something soft (eg. a towel or blanket) to protect the screen.

27-inch iMac memory hatch door

Press the small button at the top of the power socket (shown above), and pick out the memory hatch door above it. This is quite possible to do using just ytour fingers. Try to avoid using something to help lever the door open as you might scratch your Mac. Get someone with longer, strong fingernails if that helps. You really don't need much pressure to open this door.

Open iMac memory hatch door

You'll now see the two 4GB memory DIMMs that Apple ships as standard with its iMacs.

Apple illustrates how the RAM should be fitted on the back of the memory hatch door.

27-inch iMac memory install DIMM instructions

27-inch iMac memory hatch door DIMM slots 1

Now pull out the little arms to raise the iMac RAM slots.

27-inch iMac memory hatch door DIMM slots 2

Now add your two new DIMMs in the empty slots. There's no need to remove the existing memory chips, unless you're adding four new 8GB DIMMs for the maximum 32GB memory installation.

27-inch iMac memory install DIMM slots 3

Press back the small levers so that the DIMMs are back flat.

27-inch iMac memory install DIMM slots 4

Put the door back on so that it clicks back into place. You don't need long fingernails for this!

27-inch iMac memory install DIMM door

That's it. You've just increased the performance of your 27in iMac for a fraction of the cost that Apple would prefer you paid it at the point of sale.

We added two 8GB RAM DIMMs so that we got 4GB + 4GB (as shipped by Apple) plus 8GB + 8GB (as bought by us for about £60), for a total of 24GB.

24GB RAM in 27in iMac Apple

Apple doesn't offer the 24GB memory option but charges £160 for 16GB. Do it yourself and save a hundred pounds!

About This Mac 24GB RAM 1

Easy!

About This Mac 24GB RAM 2