Did you turn off your PC last night? Because if you didn’t you are certainly not alone.

According to a new report this week from educational charity the National Energy Foundation (NEF) a whopping 18 percent of work PCs are never turned off at nights and weekends, with a further 13 percent left on some nights. Both rates tend to be higher still for larger companies.

The resulting wasted energy costs UK firms £115m a year and results in 700,000 tonnes of completely unnecessary CO2 emissions. That equates to 200,000 small family cars.

More pertinently for IT directors this means that a large office-based company with 20,000 staff has roughly 2,500 PCs left on unnecessarily each night, costing the firm £175,000 in electricity and increasing its carbon footprint by almost 1,000 tonnes per annum.

So what can be done? Well, according to the report, there are two options, one low tech and one high tech.

The first is to make staff fully aware of the financial and environmental repercussions of not shutting down PCs. This is of course sensible, but has a couple of major pitfalls. Firstly some IT departments actually request PCs are left on overnight so they can patch and update. And secondly power saving campaigns are notoriously ineffective – we all know our TVs should not sit on standby all night and yet very few of us get off the sofa and turn them off.

So that leaves the high tech option, namely automated software capable of turning PCs off and booting them up again from a central location.

Cynics will note that the NEF's study was commissioned by 1E, a Windows management software specialist and vendor of exactly this type of solution. However, that shouldn't make firms discount it completely, because both 1E's NightWatchma n suite (for turning Windows PCs off) and its SMSWakeUp suite (for turning them back on again) are interesting solutions to the problem.

According to Sumir Karayi, chief executive of 1E, NightWatchman is installed as a service on the desktop and can be set to turn off the machine at a certain time. At this point the software checks if the PC is logged on or not and if it is not shuts it down immediately. If the person is logged on it sends a message to the user and if after a set period there is no response it automatically saves all files and turns the machine off.

This solves the problem of people being too forgetful or lazy to turn off their PC, but does little to tackle the problem of IT administrators insisting PCs are left on in order to carry out updates.

To get round this 1E's SMSWakeUp solution exploits the fact that even when fast asleep PCs can keep one eye open. Apparently modern PCs feature something called wake-on-LAN functionality that ensures that when the machine is off (assuming it is not unplugged) it still uses up a few watts per hour keeping the network interface ticking over looking for something called a "magic packet".

SMSWakeUp can send out secure versions of these magic packets so that as soon as the PC detects them it powers up the motherboard and turns on the machine. And, hey presto, the administrator can patch away from a remote location to their heart's content.

So, given the amount of energy firms are wasting should IT managers rush out and deploy these types of solutions?

Well it is certainly an option that large firms wasting thousands of pounds a year through always on PCs should be aware of and it is worth noting that HSBC has recently confirmed it is rolling out NightWatchman in its offices as part of the bank's plan to go carbon neutral.

However, while the environmental gains of these types of solutions are indisputable IT chiefs that have to justify such an investment from a purely cost perspective will need to carry out extremely thorough ROI calculations.

Karayi says 1E's pricing model aims to deliver ROI after roughly three months. He told me that means that given you expect to save around £50 a year by turning off a PC when not in use the NightWatchman software is priced at roughly £9 per seat.

But if you are rolling out the software for every PC in your company that means you are also putting it on the four fifths of PCs that the NEF report suggests are turned off most nights. According to my back of an envelope calculations that means you could be paying £50 for a £50 saving in electricity costs.

Although, as we say, you have to be careful with your ROI calculations. As the report suggests larger firms have a higher instance of always on PCs and there are also those 13 percent of PCs that are left on for a few nights of the week. That means that for a company with a 40 percent rate of PCs being left on 1E suddenly becomes a hugely cost effective proposition - and that's before you consider the hidden costs of PCs that are never logged off, such as the fact they often sit for months without receiving updates that would make them more secure.

Either way PC management tools are an interesting solution to the growing problem of always on PCs and it is one IT chiefs at large firms should be considering.