What an hour of 3D printer time really costs

Almost everybody who sells 3D prints charges by the part but thinks in hours: “that one is five hours of printer time”. The odd thing is that hardly anybody knows what one of those hours costs.

It costs 38 cents, plastic included. Without the plastic, just for having the machine running, 13 cents.

And there is a trap inside that number that catches almost everyone who prints occasionally. Before getting to it, it is worth seeing what that hour is made of, because it is not the same hour for everybody.

The four things an hour is made of

An hour of printing, with this site's reference part, eats 10.9 grams of filament. That is enough to break the hour down:

You can check it in the calculator with one hour and 10.9 grams, with no labour, which is exactly the part that does not depend on the clock.

Look at the electricity: under two cents an hour. It is what worries every beginner most and it is, by a long way, the cheapest thing on the list. The machine works out six times more expensive than the power it draws.

What the printer costs you per year

Multiply that hour by how much you print and you get the yearly spend. With the reference part (5 h 30 each):

The power column deserves a moment. Printing two hundred parts a year, which is eleven hundred hours of machine time, the electricity comes to 19.80 €. Per year. Less than one spool costs.

If anyone has ever told you a 3D printer “sends your power bill through the roof”, there is the number. The full breakdown of the consumption is in the electricity cost calculator.

Your hour is not my hour: the grams

The 38 cents come from a part that uses 10.9 grams an hour. Since material is 57% of the bill, the moment the grams change everything changes.

And they change a lot. A thin-walled vase-mode print can run at 5 grams an hour; a solid part with high infill sits at 40 without breaking a sweat.

Between the first row and the last there is a fourfold difference, and in both the machine has been running for exactly the same time.

Getting your own number is immediate: the slicer tells you the grams and the time for any print; divide the grams by the hours and there are your grams per hour. To sharpen it, do it with three or four of the parts you actually print and take the average.

What if the printer cost three times as much

The other half of the number is what you paid for the machine. Those 11 cents of depreciation assume a 400 € printer; with a 1,500 € one the sum is a different sum.

A 3,000 € machine makes the hour nearly three times more expensive than a 400 € one. That does not make it a bad buy: if it prints twice as fast, every part goes through half the hours and the sum comes out much the same. But that belongs in the field, not in your head.

What is a bad combination is an expensive machine used rarely, because the two effects multiply. A 1,500 € printer in the hands of somebody making twenty parts a year depreciates at 2.82 € an hour, and the reference part lands at 21.48 € of cost and 32.22 € of price.

That is worth seeing before you buy, not after.

What about printing at night?

The third variable is your power tariff, and it is the weakest of the three, even though it is the one people ask about most.

Between the cheapest tariff and the dearest, the hour moves by three cents. And going from an average tariff to a night rate, printing two hundred parts a year, saves 9.24 € a year: half a spool.

So yes, printing at night is slightly cheaper, but not enough to organise your week around. If you want the detail of the consumption it is in the power calculator; if you are worried about the spend, look at the grams first, because they cost twelve times what the power does.

The trap: depreciation assumes you will wear the machine out

Here is the problem, and it is a criticism of this very calculator's default value.

Those 11 cents of depreciation come from splitting 450 € — the printer plus the maintenance — across 4,000 hours of service life. The arithmetic is right, but it only holds if you actually reach those 4,000 hours.

And 4,000 hours is 727 parts of 5 h 30. If you give the machine five years of use, that is 146 parts a year, nearly three a week, every week, for five years.

Print less than that and you will never use the service life up: the printer will go out of date, or break with no spares available, or you will simply stop using it. And then the 11 cents are fiction.

At twenty parts a year, the machine hour does not cost 11 cents but 82: seven times more.

What that does to your price

The difference is not academic. With the corrected depreciation, the reference part goes from carrying 62 cents of machine to carrying 4.50 €:

84% more. If you sell now and then and charge 7.66 € for that part, you are not making 2.55 €: you are losing 1.72 €, because the machine is wearing out faster than you are charging for it.

You can see it yourself in the calculator with the service life set to 550 hours.

What to put in the service life field

The fix is not to change the formula: it is to put an honest number in that field. And the honest number is not what the machine can take, it is the hours you are going to give it.

It is a one-line sum: hours you print a year × years you expect to keep it, capped at the 4,000 hours of real life.

• You print now and then, around 20 parts a year: put 550.
• You sell a little, around 50 a year: put 1,375.
• You sell seriously, around 100 a year: put 2,750.
• You are near 150 or above: leave the 4,000, that is already realistic.

If you do not know how many hours you print, most slicers keep count, and if yours does not, look at how many spools you get through in a year: every kilo of PLA is around 92 hours of printer time with this part.

And if the number comes out ugly, do not dress it up. A price that does not cover the machine is a price that is quietly eating your printer.

Why a long print works out better per hour

There is one thing that does not change with the length of the print: you. Taking the part off, removing supports and packing it are the same fifteen minutes whether it took one hour or two days.

Spread across machine hours, those fifteen minutes do this:

The same machine hour, counting your time, costs seven times more on a one-hour print than on a forty-four-hour one.

Two pieces of advice come out of that, and they are worth more than any slicer setting: batch small parts onto one plate instead of printing them one by one, and do not be afraid of long jobs, which are the ones that make the best use of both the machine and your time.

Why charging by the hour almost never works

Once you know what an hour costs, the temptation is to charge by the hour, like a workshop. It rarely works out, and the first table explains why.

Of the 38 cents an hour costs, 57% is material, and the material does not depend on the clock, it depends on the part. Two five-hour prints can take 10 grams or 300 depending on how solid the part is, and charging the same for both means losing money on one and scaring the customer off on the other.

And your labour does not follow machine hours either, which you have just seen: the same quarter of an hour is worth 3.00 € an hour on a short print and 7 cents on a long one. For that same reason twice as big costs four times as much, not eight.

The hourly cost is for something else, and it is genuinely useful: deciding what goes on the machine. When you have to choose between two jobs, the one that leaves more profit per printer hour is the one that should go first, and that is what the break-even point works out.

What this hour does not include

Three things stay outside the 0.38 €, and it is worth keeping them in mind before you use that number for anything serious.

Your time. Deliberately: the fifteen minutes of handling are not per printing hour, they are per part, and folding them in here would give a number that changes with how long the print takes.

One-off spare parts. The 50 € of maintenance in the calculator is an estimate for nozzles, belts and build sheets across the life of the machine. If your printer gives you trouble, raise that field: it goes into the depreciation and pushes the hourly cost up.

The space you keep it in. If the printer takes up a room you pay for, that is a fixed monthly cost and it does not go by the hour. It belongs in the division done by the break-even point, next to your subscriptions.

The whole formula, so you do not have to take my word for it

None of the above is magic. The hour is four sums and one multiplication, and it fits on a napkin:

• Material: grams per hour ÷ 1,000 × what a kilo costs you.
• Power: watts ÷ 1,000 × your tariff per kWh.
• Machine: (what it cost + maintenance) ÷ hours of service life.
• Failures: multiply the three added together by 1.10 if you allow for 10% of prints going in the bin.

With this article's numbers: 10.9 ÷ 1,000 × 20 = 0.2180 of material; 120 ÷ 1,000 × 0.15 = 0.0180 of power; 450 ÷ 4,000 = 0.1125 of machine. They add up to 0.3485, and times 1.10 that gives 0.3834 €. The 38 cents from the opening.

If your result does not match the calculator's, it is nearly always one of three things: the hours of service life, the grams per hour, or the failure percentage. Never the power tariff.

Do it with your own numbers

Three numbers and you have it.

One. What the printer cost you, plus what you reckon you will spend on spares while you own it.

Two. The hours you are really going to give it: hours a year times the years you expect to keep it, capped at its real life.

Three. Your power tariff, which is on your last bill and which almost never changes anything.

Put the three into the cost calculator and compare the result with what you have been charging. If it comes out higher, it is not that the calculator exaggerates: it is that the machine was being paid for out of your own pocket.

More tools and guides

• How much does 3D printing cost: 20 parts with real numbersThe real cost of 20 typical 3D printed parts: keyring, planter, phone stand, gear and more, with their grams, their hours and a link to recalculate.
• Why 3D prints fail and what it really costs youA failure halfway through costs 2.96 €, and only 32% of that is material. The four causes in order, with the real annual cost of each failure rate.
• How long does a 1 kg filament spool lastHow many metres and how many parts you get from a 1 kg spool, by material and diameter. Tables for PLA, PETG and ABS, and how to gauge what is left.
• 3D printing cost calculatorWork out the real cost and selling price of a 3D printed part: material, power, machine wear, failures and markup. Free, no sign-up, nothing uploaded.
• How much to charge for a 3D printed partPrice your prints properly: real cost, your labour and your markup. Generates a quote you can copy and send straight to the customer.
• How much electricity does a 3D printer useWork out your 3D printer's power use and what it costs per month on your own tariff. With the average wattage of the most common models.

Tools Guides