If you are specifying a printed part for a business, this is the only material decision you will make most of the time. PLA is the default: cheapest, crispest, most predictable. PETG is the upgrade you reach for when the part has to survive something. Everything below is written to get you to the right one first time, because the expensive version of this decision is finding out in July.
Key takeaways
- PLA softens at around 55 °C. PETG holds its shape to roughly 75 °C. That single difference decides most commercial jobs.
- Anything that sits in a vehicle, behind glass, near a motor or above a wash-down cycle should not be PLA.
- PLA is stiffer and holds finer detail; PETG bends before it breaks, which is what you want from a working part.
- Neither is a genuine outdoor material. For a part that lives outside for years, specify ASA instead.
- The filament difference on a typical 40 cm³ part is about 12p. Never choose PLA over PETG to save money.
The decision, in one question
Where does the part live, and what does it have to survive there? Not what it is for, not what it looks like: where it physically sits for the next few years, and what that place does to plastic. Answer that and the material chooses itself.
Specify PLA when the part lives indoors at room temperature, out of direct sunlight, and is not expected to flex, take impact or get wet. That covers display and retail fittings, fit-check prototypes, form models, exhibition mounts, bench jigs and anything essentially presentational.
Specify PETG when the part goes into a vehicle, a garden, a bathroom, a kitchen, a workshop or a warehouse, or anywhere it will be dropped, bent, clamped, washed or heated. Also specify PETG when you genuinely do not know where it will end up, because its temperature ceiling is 20 °C higher and its failure mode is far more forgiving.
Heat: the number that settles most jobs
PLA starts to soften at around 55 °C. PETG holds its shape to roughly 75 °C. Those two figures decide more jobs than every other consideration on this page combined, and they are the reason a perfectly good part fails six months after delivery.
The case we see most often is a vehicle. A phone cradle, a vent mount, a telematics bracket: printed in PLA, fitted in March, perfect. Then the van sits on a terminal apron in July with the sun on the windscreen, the cab passes 60 °C, and the mount does not snap. It sags. It droops slowly out of shape, taking whatever it was holding with it, and it never comes back. That is not a print-quality problem or a design problem. It is PLA behaving exactly as PLA behaves at 60 °C.
The same failure turns up in a south-facing shop window, behind a radiator, inside an enclosure full of electronics, on a bar during service and in anything that goes through a commercial dishwasher. A useful rule of thumb: if the part will ever be somewhere you would not leave a chocolate bar, PLA is the wrong specification.
How each one fails, and why that matters
This is where the folklore is worst. PLA is not weak. Measured as raw tensile strength it usually tests higher than PETG, and it is noticeably stiffer. Clamp both in a rig and pull, and the PLA sample often takes more force before it lets go.
What matters in a working part is not peak strength but what happens at the limit. PLA is brittle: it takes load, takes more load, then fails suddenly with a clean snap and no warning. PETG is ductile: it bends, whitens at the stress point and deforms visibly before it tears. As a rule of thumb rather than a specification, elongation at break for these filament classes runs in single figures for PLA and well into double figures for PETG.
For a bracket, clip, hinge or anything handled by staff, that difference is the whole argument. A PETG clip that bends and springs back is doing its job. A PLA clip that is ten per cent stronger right up to the moment it shatters is not.
| Property | PLA Basic | PETG HF |
|---|---|---|
| Nozzle temperature | 200–220 °C | 230–250 °C |
| Bed temperature | 55–60 °C | 70–85 °C |
| Softens at roughly | 55 °C | 75 °C |
| Stiffness | High | Moderate |
| Failure mode | Brittle snap | Bends, then tears |
| Overhangs and bridging | Excellent | Fair |
| Water and damp | Poor over time | Good |
| Direct sunlight | Poor | Fair |
| Density | 1.24 g/cm³ | 1.27 g/cm³ |
| Our price per kg | £14.00 | £16.00 |
Outdoors, damp and chemicals
Neither of these is really an outdoor material, and this is the part most comparisons get wrong by being too generous to PETG.
PLA outdoors is a short story. Ultraviolet attacks it, damp gets into it, and within a British year it typically chalks and becomes brittle enough to snap between finger and thumb. It is often described as biodegradable, which is true only under industrial composting conditions: a PLA part in a yard will not meaningfully break down, it will just go brittle.
PETG does much better. It shrugs off rain, tolerates a decent range of cleaning chemicals and does not soften in the sun the way PLA does, so it will give you a season or several in a sheltered position. But it is not ultraviolet-stable in the way an engineering outdoor plastic is: over years it yellows and loses toughness.
If a part genuinely has to live outdoors: a seafront fitting, a glasshouse clip, signage hardware, anything on a vehicle exterior : the honest answer is neither. It is ASA, which was formulated for exactly this and which we run enclosed at £19.00 per kilogram. Every filament we stock is listed with prices on the materials page.
What each demands on the machine
PLA prints at roughly 200–220 °C with the bed at 55–60 °C and the cooling fan flat out. That aggressive cooling is why PLA produces the sharpest overhangs and the most reliable bridges of anything we run.
PETG wants 230–250 °C, the bed at 70–85 °C and the fan turned down to between a third and a half, because the layers need time to weld to each other. Cool PETG hard and you get a handsome part that splits along a layer line the first time it is loaded. Turning the fan down costs overhang quality, so PETG parts want more generous chamfers and shorter unsupported spans: a design decision, covered in the designing for 3D printing guide.
Finish, and what it costs in labour
PLA wins on appearance, comfortably. It holds crisp edges, small text and fine surface texture better than PETG because it sets faster and moves less as it cools. Matte PLA in particular is excellent for anything a customer will hold or photograph.
PETG has a slight glassy translucency and a tendency to string. Well-tuned retraction and a dry spool control it, but on a part with many separate towers you will still see more clean-up than the PLA equivalent, and clean-up is labour, the largest line in almost every small print job.
What the difference actually costs
PLA Basic is £14.00 per kilogram here and PETG HF is £16.00. PETG is also slightly denser, so the same geometry comes out a touch heavier. Put those together and a 40 cm³ part carries about £0.69 of PLA against roughly £0.81 of PETG.
About 12 pence. On a part quoted in double figures once file checking, slicing, machine time, plate handling and inspection are counted, the material upgrade is a rounding error, filament is rarely more than a tenth of the price of a small job, as the guide to 3D printing costs in the UK sets out line by line.
Which is the real conclusion. Nobody should choose PLA over PETG to save money. Choose PLA because it is sharper, stiffer and prints more reliably. Choose PETG because the part needs to survive.
Specifying it: a checklist by environment
Indoors, room temperature, presentational: PLA. Retail display, exhibition mounts, form models, fit checks, bench jigs, anything photographed. Matte PLA if a customer will hold it.
Indoors, working, warm or wet: PETG. Front of house, kitchens, workshops, warehouses, production fixtures, anything washed down or clamped repeatedly. PETG-CF where a fixture must stay dimensionally honest under constant load.
In or on a vehicle: PETG at minimum, ASA for anything on the outside or under a bonnet. Never PLA, whatever the season when it is fitted.
Permanently outdoors: ASA. Not PETG, and certainly not PLA. This is the one case where paying more per kilogram is genuinely the cheaper option over three years.
One last practical note for anyone iterating a design: if the finished part will eventually be PETG, print the first version in PLA anyway. At that stage you are testing geometry, not durability. Switch material once the shape has stopped changing, then order the batch. Our tolerances and the work we will not take on are set out on the capabilities page.