PLA vs PETG for outdoor 3D prints: which handles heat and sun?
For a part that stays indoors, choosing between these two is mostly a matter of taste. It gets serious when the part goes on the porch, in the yard, in the car or next to something that gets hot. Then the number that matters is the temperature at which each plastic starts to give, and the rest (sun, moisture, stiffness and how easy it is to print) settles the cases in between.
Where each one softens, according to the manufacturers
The figure that matters for a part in the heat is HDT (heat deflection temperature): the temperature at which a test bar of the material, under a standard load, starts to bend. Manufacturers measure it under ISO 75, and the values below are for the 0.45 MPa load. They vary with the brand, the color, the formulation and even how the test bar was printed; Prusa's own datasheet notes that values depend heavily on print settings. Treat them as a range, not an exact number.
| Material | Prusament | Bambu Lab | Polymaker |
|---|---|---|---|
| PLA | 55 °C (131 °F) | 57 °C (PLA Basic) | 60 °C (PolyLite PLA) |
| PETG | 68 °C (154 °F) | 69 °C (PETG HF) | 78 °C (PolyLite PETG) |
| ASA | up to 93 °C (knowledge base) | 100 °C (212 °F) | — |
Sources: each manufacturer's technical data sheet (TDS), checked November 2026; for Polymaker, the PolyLite PETG data sheet; for Prusa's ASA, its knowledge base article.
So how hot does a car get? A 2018 study by Arizona State University and UC San Diego measured cars parked in the sun for one hour on summer days in Tempe, Arizona: cabin air averaged 116 °F (47 °C), steering wheels 127 °F, seats 123 °F and dashboards 157 °F (69 °C). In the shade, dashboards averaged 118 °F (48 °C).
What that means in practice:
- Phone mount on the dashboard, part on the rear deck: PLA will deform. PETG is at its limit, and a dark part or one under load can give. ASA is the safe pick.
- Part inside the car out of direct sun, like a clip on an AC vent: PETG usually copes; PLA may give in summer.
- Part on a porch or in the yard, in the sun: dark colors get much hotter than the surrounding air. Light-colored PETG is the minimum; ASA is ideal.
- Part indoors near a window: PLA usually works, but under constant load and warmth it can slowly sag over weeks (creep).
Sun, rain and moisture
Sun is not just heat: ultraviolet light ages plastic. Prusa says PLA "degrades under UV light" and is not suited to outdoor use. For PETG, Prusa says it works for mechanical parts both indoors and outdoors; in practice it handles the outdoors much better than PLA, but in direct sun for a long time it can fade and lose strength. ASA is the material Prusa recommends for outdoor use precisely because of its UV and temperature resistance.
Rain is not a problem for a finished part in either material. Moisture matters earlier, on the spool: PETG absorbs water from the air and, when wet, prints with strings, bubbles and a dull surface. Polymaker recommends drying PETG at 65 °C (149 °F) for 6 hours, and Bambu Lab says PETG HF must be dried before use. The step by step is in the guide to drying wet filament.
Stiffness or toughness
PLA is stiffer: a PLA shelf bracket flexes less. But when it fails, it snaps all at once, without warning. PETG is tougher: it bends before it breaks, takes knocks and is better for clips, snap fits, living hinges and parts that get bumped. PETG's layer bonding is usually good too. For a part that has to stay straight and still, PLA wins; for one that has to flex and take abuse, PETG does.
Printing PETG takes more care
| PLA | PETG | ASA | |
|---|---|---|---|
| Nozzle (Prusa's recommendation) | 210–215 °C | 230–240 °C | 260 °C |
| Bed (Prusa's recommendation) | 60 °C | 85–90 °C | 105–110 °C |
| Ease of printing | The easiest | Stringing and adhesion need tuning | Warps; needs an enclosure |
| Smell | Low | Low | Strong; ventilate |
| Sun (UV) | Degrades, per Prusa | Handles moderate outdoor use | Made for sun |
| Food contact | Avoid | Prusa does not recommend it | Avoid |
Other brands give similar ranges: Polymaker, for example, lists 230 to 260 °C at the nozzle and 70 to 80 °C on the bed for PolyLite PETG. Follow the label on your spool.
The three things that make the most difference with PETG:
- Stringing. PETG oozes more than PLA. Prusa suggests more retraction and a cooler nozzle; dry filament helps a lot. All of that is in the guide to PETG stringing.
- Too much grip on smooth PEI. PETG bonds so hard to smooth PEI that it can tear chunks out of the surface. Prusa advises against using its smooth PEI sheet with PETG, or applying glue stick first; Bambu Lab also calls for glue on its smooth plate for filaments other than PLA. Here the glue is not there to stick better but to release: it works as a separation layer. On textured PEI it is generally not needed.
- A first layer that is not squished. With the nozzle too close to the bed, PETG builds up on the nozzle and drops blobs on the part. A first layer slightly higher than for PLA usually fixes it.
What each part costs
PETG is a little denser than PLA (1.27 vs 1.24 g/cm³), so the same part weighs about 2% more. With both at $20/kg, an 85 g PLA part ($1.70) becomes 87 g in PETG ($1.74). PETG profiles tend to print slower, and the extra time costs money too: with the calculator's US starting values (120 W at $0.17/kWh, a $600 printer with a 6,000-hour useful life and $0.05/h for maintenance), machine time comes to about $0.17 an hour, so each extra half hour adds about $0.09. The difference is small: choose by what the part has to do, not by price.
When to switch to ASA
If the part will sit in the sun all year (an antenna mount, an exterior car part, a porch planter, a sensor box), ASA is the material made for it: Prusa highlights its UV resistance and temperature resistance up to 93 °C (199 °F), and Bambu Lab's datasheet lists an HDT of 100 °C (212 °F). The catch is printing it: it warps, needs an enclosure for larger parts, a bed above 100 °C and ventilation, because it gives off fumes. If your printer is open-frame, read the guide on how to choose a 3D printer before you buy a spool.
Frequently asked questions
Can I leave a PLA part in my car?
Out of direct sun and with no load, it sometimes survives; on the dashboard or the rear deck, no. The Arizona State University study measured dashboards at 157 °F (69 °C) after an hour in the sun, above the HDT of PLA from every manufacturer in the table. For any car part, go with light-colored PETG or ASA.
Does annealing PLA or PETG improve heat resistance?
Annealing (heating the finished part in an oven, below its melting point) can raise the heat resistance of some PLAs, but the part shrinks and may warp, so dimensions change. Bambu Lab advises against annealing PETG HF: its datasheet says the gain is small and that parts with more complex shapes can deform.
Can PLA or PETG prints go in the dishwasher?
PLA, no: the hot water in many cycles gets close to the range where it softens. PETG handles more, but it can still deform on hot cycles, and layer lines trap residue. Hand-wash in warm water.
Why is neither one recommended for food?
The issue is not just the plastic. The gaps between layers hold food residue and bacteria, pigments and additives vary by brand, and the filament passes through a nozzle and extruder that are not made for food. Prusa notes that PETG is used in the food industry but still does not recommend printed parts for it.
Does a light or dark color matter in the sun?
Yes. A dark part absorbs more light and gets much hotter than the surrounding air, while a light one reflects part of it. For outdoor parts, white, light gray or other light colors give you extra temperature headroom, and they fade less visibly too.