Filament dryer power calculator: kWh and cost per drying run

The formula

A dryer’s heater runs flat out while the box warms up, then switches on and off to hold the temperature. Over a whole run it averages a fraction of its rating.

average W      = rated watts x average share
kWh per run    = average W x hours / 1000
cost per run   = kWh per run x price per kWh
cost per spool = cost per run / spools in the run
cost per month = cost per run x runs per month

The average share is the one number the rating cannot tell you. It depends on the temperature you set, the room temperature and how well the box holds heat. A smart plug energy monitor measures it directly: enter its average reading as the rated power and set the share to 100%.

Where the defaults come from

The defaults are a real measured run. Elegoo publishes a reference consumption for its H1 HT dryer: 0.386 kWh over 8 hours at 85 °C, at 220 V in a 25 °C room. Its rating at 220 V is 150 W. An 8-hour run at 150 W would use 1.2 kWh, so the measured run averaged 32% of the rating. The calculator applies that 32% to the H1 HT’s 110 V rating of 130 W.

The electricity price is the U.S. Energy Information Administration (EIA) average residential price for July 2026, 18.31 cents per kWh. Four runs a month is a placeholder for your own use.

How much electricity does a filament dryer use?

Single-spool filament dryers are rated from 48 to 170 W, and four-spool models from 300 to 360 W. Each one averages well under its rating once it reaches temperature. Elegoo measured 0.386 kWh for an 8-hour run at 85 °C on its 150 W H1 HT, an average of about 48 W.

Rated power by dryer

From each maker’s own page. These are the calculator’s presets.

Dryer	Rated power	Spools	Highest temperature
SUNLU FilaDryer S2	48 W	1	70 °C
Polymaker PolyDryer	68 W	1	73 °C
Bambu Lab AMS 2 Pro, drying	80 W	4	65 °C
Elegoo H1 HT	130 W at 110 V	1	85 °C
Creality Space Pi	145 W	1	70 °C
Bambu Lab AMS HT, drying	170 W	1	85 °C
SUNLU FilaDryer S4	300 W	4	70 °C
SUNLU FilaDryer E2	325 W	2	110 °C
Creality SpacePi X4	360 W	4	85 °C

Some makers publish two figures for the same dryer, and the calculator uses the rated input:

• SUNLU S4. The specification lists 300 W rated power, and the product copy describes a 350 W heater.
• Creality Space Pi. The store lists 145 W rated power, and Creality’s blog describes an 80 W heater.
• Bambu Lab AMS HT. The wiki lists 170 W while drying, and the store lists 150 W average power.

What testers measured

Test	Conditions	Measured	Average draw
Elegoo, H1 HT reference figure	8 h at 85 °C, 220 V, 25 °C room	0.386 kWh	48 W
CNC Kitchen, dryer not named	two PETG spools, 6 h at 60 °C	0.6 kWh	100 W
3D Print Beginner, Sovol dryer rated 48 W	conditions not stated	close to 40 W	40 W

The share varies a lot. The Elegoo run averaged 32% of its rating, and the Sovol reading came close to 83% of its 48 W. Treat the 32% default as one measured case, and measure your own dryer when you can.

How much does it cost to dry a spool of filament?

Usually a few cents. At the US average of 18.31 cents per kWh, the default 8-hour run on Elegoo’s H1 HT uses 0.33 kWh and costs about 6 cents. CNC Kitchen measured 0.6 kWh to dry two PETG spools for six hours. That comes to 11 cents, or 5.5 cents a spool.

Worked example with the defaults

1. Average draw: 130 W x 32% = 41.6 W.
2. Energy: 41.6 W x 8 h / 1000 = 0.333 kWh.
3. Cost per run: 0.333 x $0.1831 = $0.06.
4. Cost per month at four runs: $0.24.

Fuller dryers cost less per spool

A multi-spool dryer costs more per run and less per spool when it is full. At the same 32% share, an 8-hour run on the 300 W SUNLU S4 uses 0.77 kWh, 14 cents for four spools, or 3.5 cents each. The 145 W Creality Space Pi uses 0.37 kWh, about 7 cents for its one spool. Run a big dryer half empty and the advantage goes.

Drying time drives the bill

Energy rises in step with hours, so the drying time you choose matters as much as the dryer. Makers’ times differ. Bambu Lab’s wiki gives 8 hours in a forced-air oven for PLA, PETG, ABS and PC. Prusa’s knowledge base gives 4 to 6 hours for most of its Prusament materials at their own temperatures. Use the time your filament’s maker gives, then check the result. The wet filament checklist lists the signs that a spool is still wet.

Measure your own dryer

Plug the dryer into a smart plug that logs energy, run a normal drying cycle and read the kWh at the end. Divide by the hours for the average watts. Enter that as the rated power with the share at 100%, and the calculator’s monthly figure becomes a measured one. The electricity cost calculator does the same for the printer itself.