Acaia Lunar 2021 Smart Espresso Scale

Before using the Acaia Lunar for the first time, place it on a stable, vibration-free, and level surface. The Lunar is sized specifically to fit on the drip tray of most espresso machines — position it so the weighing pan sits squarely under the portafilter or spout. Avoid surfaces near strong heat sources, fans, or vibrating equipment, as these will affect accuracy.

Charge the scale before first use by connecting the included USB Type-C cable to a standard USB wall charger (5V/1A output). Do not use fast-charging adapters or USB hubs delivering more than 5V/1A — these can damage the circuit board. A full charge takes approximately 1–2 hours. The Lunar has a built-in charging protection circuit: if the scale surface is hot from recent brewing, charging will not begin until the scale cools down. This is normal behavior.

To power on, press the Power button. To power off, double-tap the Power button. On first use, the scale will start in Weighing Mode, displaying [ 0.0 ]. Place the non-slip protective strips on the underside corners of the scale if desired for added grip on the drip tray, and the friction-reduction strips on the sides if your drip tray has rails.

To check battery level: with the scale off, press and hold the Power button. The display will show [ ACAIA ], then [ SEt ]. Continue holding until the battery percentage appears. Release to exit without entering settings.

To calibrate: with the scale on and in Weighing Mode (grams), rapidly tap the Tare button repeatedly until [ CAL ] appears. Place the included 100g calibration weight on the center of the weighing pan and wait until the display shows [ _End_ ]. Calibration is complete. Acaia recommends recalibrating periodically or whenever the scale has been moved or dropped.

Understanding the Six Modes

The Lunar has six brewing modes. Press and hold the Power button while the scale is on to cycle through them. The active mode is indicated by icons on the LED display.

Mode 1 — Weighing Mode

Displays weight only in grams or ounces (0.1g readability). Use for general weighing tasks. Tare Save is supported in this mode: press and hold Tare for 2 seconds to save a container weight; press and hold for 0.5 seconds to subtract that saved weight from the reading.

Mode 2 — Dual Display Mode

Displays timer (left) and weight (right) simultaneously. Tap the Power button to start, stop, or reset the timer manually. Use for any timed brew where you want to start the clock yourself. Tare Save is also supported here.

Mode 3 — Timer Starts with Flow (Droplet icon)

The timer starts automatically the moment the Lunar detects the first drip of espresso flow, and stops when flow ceases. Place a cup on the scale, tare manually with the Tare button, then pull the shot. Best for hands-free shot timing where you want to capture only the extraction time.

Mode 4 — Auto-Tare, Timer Starts with Flow (Droplet + Square icons)

When a stable weight is placed on the scale (your cup), the scale auto-tares. The timer then starts automatically when espresso flow is detected, and stops when flow stops. Ideal for workflow where you set the cup and walk away — no button presses needed.

Mode 5 — Auto-Tare, Auto-Start Timer (Triangle + Square icons)

The scale auto-tares when a stable weight is placed on it, then immediately starts the timer. Use this mode to capture the full shot time including pre-infusion. The timer stops when espresso flow stops. When the cup is removed after brewing, the display flashes the final beverage weight and average flow rate.

Mode 6 — Auto-Tare Only (Square icon)

The scale auto-tares when a stable weight is placed on it, with no timer. Pull your shot normally. When the cup is removed, the brewing summary (final weight and average flow rate) is displayed briefly.

Flow-Rate Indicator

An LED bar across the top of the display visualizes real-time espresso flow rate from 0.1 g/s (left) to 3.4 g/s (right). During a brew, a single bright LED marks the peak flow rate reached so far. When the cup is removed after brewing, the display flashes between the final beverage weight and the average flow rate for that shot. The Flow-Rate Indicator can be enabled or disabled in the Configuration menu (FLorAtE.d setting).

Tare Save

In Modes 1 and 2, you can save the weight of a frequently used vessel. Place the empty vessel on the scale and press and hold Tare for 2 seconds to store its weight. To subtract that stored weight in future, press and hold Tare for 0.5 seconds — the scale will display the net contents weight.

Configuration Menu

With the scale powered off, press and hold the Power button until the display shows [ ACAIA ] then [ SEt ]. Release. Tap Tare to navigate settings, press and hold Tare to enter and confirm a setting. Key settings include Sleep Timer (default 5 min), Brightness (1–4), Battery Saving (display dim delay), Key Sound (beep on/off), individual Mode on/off toggles, Flow-Rate Indicator style, Auto-Reset delay, Weighing Filter (Fast/Normal/High), and Bluetooth on/off. To reset all settings to factory defaults, navigate to [ rESEt.d ] and select Yes.

Connecting to the Acaia App

Download the Acaia app (iOS or Android) and enable Bluetooth on your phone. Power on the Lunar — it will broadcast automatically when Bluetooth is enabled in settings. Use the app to log brews, adjust settings remotely, update firmware, and view historical shot data.

Routine Cleaning After Each Use

Wipe the weighing pan and the scale body with a soft, slightly damp cloth after each brewing session. The Lunar has a water-resistant design but is not fully waterproof — avoid submerging it or allowing water to pool on the surface or enter the button area. Always dry thoroughly after wiping.

Cleaning Products to Avoid

Use warm water only. Do not use detergents, alcohol, bleach, or any chemical cleaners. These will damage the anodized aluminum coating, degrade the surface finish, and may compromise the waterproofing.

Weighing Pan and Protective Strips

The weighing pan can be carefully lifted off the scale body for cleaning. Rinse it under warm water, dry completely before replacing. If the non-slip or friction-reduction protective strips on the underside have come loose or become dirty, wipe them clean with a damp cloth. Replace them if they lose their grip.

Button Area

The Power and Tare buttons use a sealed touch-sensitive design. If water enters a button — indicated by [ _H2O ] or [ H2O_ ] on the display — dry the scale thoroughly with a cloth and allow it to air-dry completely before use. Do not press buttons if water ingress is suspected.

Long-Term Storage

If storing the scale for an extended period, charge the battery to approximately 50–80% first. Store in a cool, dry location away from direct sunlight. Avoid exposing the scale to extreme temperatures or humidity.

Scale Won't Turn On

Charge the scale using the USB Type-C cable and a 5V/1A adapter. Do not use fast-charging adapters. If the scale has been fully depleted, it may take a few minutes on the charger before it will power on. Check that the charging cable is properly seated — the charging indicator LED should light up.

Scale Not Charging

The Lunar has charging protection that prevents charging when the scale surface is hot from brewing. Allow the scale to cool fully and try again. Also confirm your charger outputs exactly 5V/1A — charging hubs and fast-chargers exceeding this specification will not charge the scale and may damage it.

Timer Not Starting Automatically (Flow Modes)

The flow-detection modes are calibrated for the slow trickle of espresso. Very fast or inconsistent pre-infusion may confuse the sensor. Make sure the cup is placed on the scale and tared before pulling the shot. If using Mode 3, tare manually before extraction. If using Modes 4 or 5, place the cup and wait for auto-tare to complete before starting the pump. The flow detection will not reliably trigger from a kettle pour — use Mode 2 or 3 for pour-over.

Inaccurate or Drifting Weight Readings

Place the scale on a completely flat, stable surface away from vibrations and air currents. Recalibrate using the included 100g weight (rapidly tap Tare until [ CAL ] appears, place weight, wait for [ _End_ ]). Check that the Zero Tracking setting is not set to Off — Acaia recommends leaving it at 1d or 2d for the Lunar. If readings still drift, the scale may be on a surface with vibration from the espresso machine pump; use the non-slip pads to isolate it.

Display Shows Error Code

Error 100 indicates an unrecognized access code. Errors 101 and 102 indicate hardware faults — contact Acaia support at support@acaia.co. Error 303 indicates the load cell may have been damaged by excessive force or a drop — contact Acaia support. Error 304 means calibration failed due to environmental noise; move to a stable environment and recalibrate. [ _H2O ] or [ H2O_ ] means water was detected in the button area — dry the scale thoroughly before use.

Scale Auto-Resets Too Quickly Between Shots

The Auto-Reset timer defaults to 30 seconds after the cup is removed. If this is too fast for back-to-back shots, increase the [ Auto_rES ] setting in the Configuration menu to a longer value, or set it to Off.

Bluetooth Won't Connect

Ensure Bluetooth is enabled in the scale's Configuration menu ([ bt_SEt ] = On). Force-quit and reopen the Acaia app. If the scale still doesn't appear, try resetting the Bluetooth connection in the app, or reset the scale to factory defaults ([ rESEt.d ] = Yes) and re-pair.

Warranty and Support

The Acaia Lunar carries a 2-year manufacturer warranty. For warranty claims or technical support, contact Acaia directly at support@acaia.co.