Printer ink subscription services can work out cheaper than regular ink, but it’s marginal and can be complicated to calculate. The real benefit of the system is that you get ink delivered to your door before your current ink cartridges are empty, so you won’t ever run out of ink without having a spare cartridge to hand.

Subscription services such as HP’s Instant Ink are available in page bundles, which work out cheaper on a per-page basis the more you spend. For example, £1.79 per month lets you print 10 pages, 50 pages costs £4.49 per month, 100 pages is £6.49 per month and so on. Page prices are the same whether you’re printing in colour or black and white, so it tends to be a bit better value to print in colour, because colour printing tends to be more expensive when buying cartridges normally.

You pay the monthly charge whether you print all those pages or not, so if you’re not using your paid-for allocation, the price per page increases.

You’ll also run into trouble if you go over your monthly limit. HP charges £1.50 for each set of 10 additional pages printed beyond your subscribed amount. There’s some leeway in that unprinted pages from previous months can be rolled over and form a reserve, which you can draw from when printing over your allowance. However, reserve pages expire after three months, at which point they’re wasted.