How much electrical energy does the printer use?

Hi people,

I was going to buy one of those energymeters that you can use to calculate the energycost of electrical devices, but before I do I wanted to know if anyone knew if there's maybe a simple way to calculate this yourself?

Thanks in advance,

Niles

The big energy consumers are the heated bed and extruder heater. Following these would be the stepper motors and the Melzi.

The heated bed is 1.2ohms so power used by it would be 12^2 / 1.2 = 120W.

The extruder heater is 5.8ohms so the power used by it would be 12^2 / 5.8 = 24.8W

The stepper motors are current limited at 1A and there are effectively 4 of them (Z motors in series count as one) so the power used by them would be 4 * 12 * 1 = 48W

These would represent a maximum of 120W + 24.8W + 48W = 192.8W

Of course the heaters are not active all the time and neither are all of the stepper motors so the real power usage would be less than this.

If you assume the heaters are operating at about 50% duty-cycle and the X, Y and Extruder motors are running continuously you could probably reduce it to:

60W + 12.4W + 36W = 108.4W

Allowing a few Watts for the Melzi and prevailing wind, I would say 112W is probably a good average figure. I wonder if your intended meter would agree

Regards,
Neil Darlow

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I try to write with consideration for all nationalities. Please let me know if something is unclear.
Printing with Mendel90 from fedora 25 using Cura, FreeCAD, MeshLab, OpenSCAD, Skeinforge and Slic3r tools.

Thanks for doing that math Neil! That sounds great! Up until now I thought a 3d printer would be much more expensive to use.

Edited 1 time(s). Last edit at 01/14/2014 06:40PM by Nilez.

The calculation will not be entirely accurate. There is obviously some warm-up time where the heaters are on full power and there is also Z-motor running, power supply efficiency and dummy loads to factor in. As a ball-park figure it will be somewhere near.

In terms of total energy usage for, say, a 28 minute PLA print (with 2 minute warm-up) something like:

2mins * 192.8W + 28mins * 108.4W = 0.03 * 192.8Wh + 0.47 * 108.4Wh = 5.78Wh + 50.95Wh = 56.73Wh or 0.05673kWh 'ish.

Perhaps a meter is a good idea

Regards,
Neil Darlow

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I try to write with consideration for all nationalities. Please let me know if something is unclear.
Printing with Mendel90 from fedora 25 using Cura, FreeCAD, MeshLab, OpenSCAD, Skeinforge and Slic3r tools.

I have one of those meters. I can run a print tonight and tell you all the figures if you like...

Sure QP, let's see some actual figures

The cost of the electricity is not significant compared to the cost of the filament.

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[www.hydraraptor.blogspot.com]

Quote
nophead
The cost of the electricity is not significant compared to the cost of the filament.

Given the exponential rises in energy prices (and the promise of cheaper filament from consumer-friendly pellet-fed filament extruders!) for how long do we think this statement will hold true?

Right, here are the figures from my print job last night.

Idle (just powered up, doing nothing): 19W, 0.13A

I have an early 2013 kit Mendel90 with Panelolu2 display, OctoPi disabled for this test, ABS print direct from SD card, no extruder fan used.
My gantry has 12V LEDs adhesive strips fitted for bed illumination which I now leave on throughout the print but current draw from these will be in the region of mW.

Bed warmup phase: 172W, 0.95A (this dropped to 146W, 0.83A when the steppers switched off, and gradually reduced to about 120W during entire the warmup process)
E target temp = 0C
B target temp = 125C
Duration = 10m
The nozzle was centred on X, moved to the front of Y and raised to Z_max at the beginning of this phase.

Extruder warmup phase: 156W, 0.89A peak (fluctuated as PIDs kicked in to maintain temps)
E target temp = 235C
B target temp = 125C
Duration = 3m
Z was lowered to just above the bed (to prevent ooze) as the E target temperatures were set, and the nozzle is at about 130C by the time the move is completed. It then waits until target temp is reached plus a further 30s stabilisation time.

Print phase: 163W, 0.87A, it's worth noting that we've only used 0.03KWH by the start of this phase, even with all that heating going on.
E target temp = 235C
B target temp = 115C (2nd layer onwards)
Duration = 2h5m

Cooldown phase (idle): 36W, 0.22A
E target temp = 0C
B target temp = 0C
Bed fan = on
Duration = 10m
Bed is moved to the back and the bed fan is switched on to accelerate cooling. If I remove the wadding at this stage then the bed can be at room temp within 10mins.

Total consumption over the entire print: 0.29KWH, which at today's already a-s-t-r-o-n-o-m-i-c-a-l* prices is still only about 5p.

So as Chris says, power consumption is negligible (though this still accounts for a lot more heat in my den - the thermostat on the wall just outside it doesn't kick in when I'm printing, which results in my wife complaining about the rest of the house being cold!)

* Why is "a-s-t-r-o-n-o-m-i-c-a-l" a banned word?!

PS - yes I know the current figures don't match the power ones, but I have to press a button to switch from A to W to KWH etc. and that gives it enough time to fluctuate. I could have taken several readings and averaged them but I got distracted (by Googling for graphing power monitors) and, err, forgot...

Those figures are lower than mine so the heating must use less power than my calculations - which I am prepared to believe.

Perhaps we should use your figures for personal costing and mine for charging customers. That way you could actually make a profit from this activity!

Regards,
Neil Darlow

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I try to write with consideration for all nationalities. Please let me know if something is unclear.
Printing with Mendel90 from fedora 25 using Cura, FreeCAD, MeshLab, OpenSCAD, Skeinforge and Slic3r tools.

Other than the theoretical maximum wattage, I think my figures are higher, aren't they?

I really should have taken multiple readings during my two hour print but I figured it was going up and down so much that actually over the course of the two hours the consumption figure would be more useful than spot figures.

My "print phase" figure of 163W is just based on watching the meter for about 5-10 minutes as the first few layers went down and averaging them in my head. I don't think it ever went up to 192.8W but it definitely went higher than 163W - this would reflect that the motors and heaters would only occasionally be on simultaneously for any prolonged period.

If you multiply the calculated figure for your half-hour PLA print by four then the result isn't far off (but still just under) my two-hour ABS print.

Remember also that the energy meter measures "at the wall", so it includes the inefficiency of the PSU. I know that the Corsair 1200AX PSU in my gaming PC is rated 90% efficient at 50% load (which coincidentally is roughly what my energy meter says it draws with all the GPU and CPU cores maxed out), and Chris keeps reminding us that these are fairly cheap ATX PSUs that come in the kit.
If you're going to factor in energy usage when charging customers then multiplying your maximum theoretical figures by the efficiency of your PSU will probably get your a much more realistic figure.

Wow guys! Thanks for digging so deep into this topic! Before I started it I really thought costs would be much higher since we're dealing with heating elements and what have you.

Edited 2 time(s). Last edit at 01/16/2014 07:35PM by Nilez.

What also gets missed out in many power consumption cost analyses is that the heat produced offsets heating costs for the room. Currently more energy efficient lights are promoted over the old warm friendly looking tunsten filament variety. If one switches to more efficient lights and one's heating is electric and the weather is cold then there might well be zero saving. The same is true for any electrical equipment - the power it uses is converted to heat.

Yes that annoys the hell out me, just as saying spending X on preventative health care will save Y lives or save money overall. Everybody dies so health care never saved a life, just lengthened it possibly and the longer you live the more likely you are to cost the health service money. And don't get me started on sustainable growth!

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[www.hydraraptor.blogspot.com]