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Power Consumption re-emerges as a key factor in printer cost savings for business

Issue #1205 – New printer and office MFP models from Hewlett-Packard and Oki demonstrate how power consumption has again been tagged as a key area for cost savings for businesses (as well as saving the planet of course). Auto-off features are used as a means of dropping power consumption to less than 1 Watt when the device is not in use.

We are now looking at almost two decades since the first emergence of power consumption as a cost-saving element. Laser printers in the 80’s and early 90’s would run at full power while printing, typically consuming anything up to around 1200 Watts or so, then falling to a stand-by mode where consumption could typically be between 70 and 250 Watts. Warm-up time could be as long as 90 seconds.

However, Sleep mode was almost unheard of two decades ago. The first devices to introduce a Sleep (or Power Save) mode could drop consumption to as little as 20 Watts but few machines were equipped with this feature. Within a very few years though, all print devices were equipped with Sleep mode.

While today’s laser MFPs will still draw between 450 and 1400 Watts while in full operation, and Idle mode can be as low as 20 or 40 Watts, the fact remains that the range of power consumption at a time when the device is not actually printing can vary dramatically. For instance, consumption in Sleep mode on some devices can be much higher than consumption in Idle mode on other devices – Sleep mode can be as high as 75 or 80 Watts compared to the Idle ratings quoted above (a factor as high as 4x).

Considering that any printer or MFP will spend most of its time NOT printing, it is essential that the design of the device permits as efficient non-operation as possible. This is the crux of the issue with regard to the latest developments in power saving technologies.

A number of devices now have an ‘Off’ power state. But, this state has different definitions. The latest devices from Hewlett-Packard and Oki have an ‘Auto-Off’ mode, which also are subject to slightly different definitions. We use devices from these two manufacturers as examples, with no suggestion that these are the only devices offering Auto-Off features.

Firstly, Oki has created an Auto-Off function that drops the device into a very low power state, default set at 4 hours of non-operation, consuming between 0.15 Watts and 0.5 Watts depending on the type of device. The time delay to Auto-Off is user-definable in 1-hour steps from 1 hour to 24 hours.

Secondly, Hewlett-Packard has created an Auto-On / Auto-Off function that drops devices into a very low lower state as low as 0.9 Watts for a colour MFP. Hewlett-Packard does not activate Auto-On / Auto-Off by default though. Users need to go into the settings to turn it on and can set the activation time to between 1 minute and 30 minutes.

What we really have to note here is the difference between these two features. Oki’s Auto-Off implementation cuts in at a point between 1 and 24 hours – in other words, of most use to reduce overnight or over weekend power consumption. By comparison, Hewlett-Packard’s implementation is capable of cutting in almost immediately, meaning that it can reduce power consumption at almost any time of day. Furthermore, the Hewlett-Packard devices can be ready for printing again within 10 seconds, largely due to the instant-on fuser design used in its laser devices.

But – the most important difference is that while Oki’s machines need to be woken from Auto-Off manually when the machine is required again, Hewlett-Packard’s devices are capable of re-awakening themselves automatically when a print job is sensed.

Historically, devices have relied on the I/O interface being active and ‘listening’ for a newly arriving job at any time, for any kind of auto-power save mode. Hewlett-Packard has now found a way around that issue by implementing an Auto-Off power save mode that allows automatic re-awakening by letting firmware do the listening rather than the interface, thus reducing power consumption by the interface.

Clearly, this makes a huge difference to the user-friendliness of the system but also reduces the overall power consumption by allowing greater efficiency in terms of the time in which the device is allowed to go into Auto-Off mode. A rapid re-awakening means there is barely any need even for an Idle mode, let alone a sleep mode – with a 10 second ready time from Off, the device could go straight from Printing mode to Auto-Off mode, and then back again when a new print job arrives, without disadvantaging users at all.

OK. This makes the Hewlett-Packard implementation sound like it is head and shoulders above the Oki implementation. But, all is not quite as it seems.

What Oki does not really make clear to the user is that some devices have a ‘Deep Sleep’ mode, dropping the device to between 1 Watt and 3 Watts, depending on the device, which is user-definable between 1 minute and 120 minutes. In this mode, the device will re-awaken automatically, making ‘Deep Sleep’ a pretty direct equivalent to Hewlett-Packard’s ‘Auto-Off’!

So, in actuality, there is very little difference between the two implementations. The main difference lies in the rapid warm-up of the Hewlett-Packard devices – oh, and the fact that Oki devices will need to be re-woken manually each morning after dropping fully into Auto-Off and drawing as little as 0.15 Watts overnight.

Let’s briefly make a comparison between one of these new generation devices and a more typical previous generation device. Let’s suppose printers:

  • are 30ppm with 15 second warm-up
  • print 20 jobs per day, comprising 5 pages each, averaging 15 minutes between jobs
  • are set for minimum default time-out, i.e.
    • 1 minute Idle to Deep Sleep / Auto-Off for the new generation device
    • 5 minutes Idle to Sleep for the previous generation device
  • power consumption while printing is 500 Watts
  • power consumption in Idle mode is 50 Watts
  • power consumption in Deep Sleep / Auto-Off mode for the new generation device is 1 Watt
  • power consumption in Power Save mode for the previous generation device is 25 Watts
  • working day is 9 hours
  • 253 working days per year

New generation device:

Printer State Time Power used
Total time actually printing per day = 8 minutes 20 seconds = 0.694kWh
Time spent in Idle per day = 20 minutes = 0.0167kWh
Working day spent in Deep Sleep
/ Auto-Off per day
= 8 hours, 31 minutes 40 seconds = 0.00853kWh
Overnight time in Deep Sleep
/ Auto-Off per day
= 15 hours = 0.015kWh
  Power used per working day = 0.73423kWh
  Power used per working year = 185.76kWh
Non-working days per year spent
in Deep Sleep / Auto-Off
= 112 days = 2.688kWh
  Total power used per year = 188.45kWh
Cost of power per kWh = €0.2 per kWh  
  Total cost of power used per year = €37.69

Previous generation device:

Printer State Time Power used
Total time actually printing per day = 8 minutes 20 seconds = 0.694kWh
Time spent in Idle per day = 20 minutes = 0.0833kWh
Working day spent in Power Save
per day
= 8 hours, 31 minutes 40 seconds = 0.1799kWh
Overnight time in Power Save
per day
= 15 hours = 0.375kWh
  Power used per working day = 1.3322kWh
  Power used per working year = 337.05kWh
Non-working days per year spent
in Power Save
= 112 days = 67.2kWh
  Total power used per year = 404.25kWh
Cost of power per kWh = €0.2 per kWh  
  Total cost of power used per year = €80.85

Per machine, this doesn’t sound like a huge power overhead for a business. However, multiply that overhead by 500 for a large business, or even by 5,000 for a multinational corporation, and we’re talking about a massive difference in cost of power per year. Work it out for your own business!! How many laser printers do you have?

Thus, we see two things:

  • Firstly, the new generation of laser printers with Auto-On / Auto-Off or automatic Deep Sleep modes really will save businesses large amounts of money in the long term
  • Perhaps, just perhaps, laser printers should be physically switched off over night and at weekends? But, remember that there will be a slight additional overhead each working day as the device is switched on again and warms up for the first time (only around 1kWh, or 20 Euro cents, per laser printer per year!)

Think about it!

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