Being unable to refill your printer's ink supply before it runs out is one of life's great mysteries: you get plenty of advance warning, but somehow you still end up making that emergency trip to the nearest supermarket.

HP is looking to save consumers and small businesses the trip with a new subscription-based ink replacement service called Instant Ink.

Launched in the US in September last year, it automatically delivers ink cartridges to your door when supplies are almost dry, removing the need to re-order. And because they're larger than ones available from retail, HP says that you'll only need to order up to three of them in a single year.

Paper trail

Instead of paying for ink, you sign up to one of three tiered price plans that allows you to print 50 (£1.99), 100 (£3.49) or 300 (£7.99) pages per month. This makes it a particularly attractive proposition for those who frequently print in colour, images or high quality as you're paying for the paper rather than the ink.

Unused pages roll over to the following month; however, they can't exceed the total number of pages of the plan that you're subscribed on (e.g. for the 50 page plan you would be able to roll over 50 pages). Printed pages are taken first from the base plan of the subscription, and then from rollover pages, and roll-over pages never expire.

Additional pages can also be printed for an extra pound should you run out before the end of the month, which releases 15, 20 or 25 pages on the respective plans.

The contract can be ended online at any time (you get to keep the printer), and subscribers are free to chop and change between plans. Cancellation is effective after the last day of the current billing period.

Compatible models

The service is only compatible with certain HP printers that feature a paper-counting sensor and the ability to report ink levels back to the company over the internet.

Compatible models include HP's ENVY 4500 series, HP Envy 5530 series, HP Officejet 4630 series and HP Officejet Pro 8610 and 8620 series, which are among the first aimed at 'small and midsized' businesses (SMBs).

While HP claims that Instant Ink can save consumers up to 70% on their regular printing costs, John Lewis estimates that it could save businesses that print up to 300 pages per month £364 per year compared to using HP's XL High Yield cartridges.

HP Instant Ink is available now from Currys, PC World and John Lewis.