Measure at the wall
Battery watt-hours are stored energy, not automatically the electricity taken from the outlet. Charging losses and dock electronics mean wall energy can be higher. A dock with dust collection, washing or drying can also have short high-power phases that a basic standby number misses.
Use cumulative kWh across several complete routines when a compatible meter and the appliance instructions allow it. Record whether automatic emptying or other dock functions were enabled.
Reset the meter only at a clear starting point and note the date, cleaning schedule and enabled features. A seven-day total can be divided by seven for a daily planning average, provided that week reflects normal use.
Calculate charging and dock time
Assume one complete charge draws 0.06 kWh from the wall and occurs 20 times in a month: 1.2 kWh. If the dock averages 3 W during the remaining 187 hours, it adds about 0.56 kWh. Total electricity is 1.76 kWh, costing roughly $0.32 at $0.18/kWh.
This is a fictional schedule. Do not add a separate efficiency penalty to the 0.06 kWh if it was already measured at the wall; the measurement includes charging losses.
For a self-emptying dock, one week of cumulative energy is often more informative than a single charge. Include normal cleaning runs and maintenance cycles, then scale the weekly total cautiously. A holiday or unusually dirty floor can make one week unrepresentative.
Count cleaning functions once
If a measurement covers the full dock and robot through charging, standby and automatic emptying, it already contains those functions. Separating them can help explain the total, but their subtotals must add back to the same measured period.
Advertised runtime does not reveal wall energy. Carpet, suction level, navigation and battery condition can change how often the robot returns to charge, while the dock configuration changes its own load.
Judge value beyond electricity
Electricity is likely to be one line in the ownership cost. Replacement filters, bags, brushes, batteries and any cleaning solution should be listed separately. Use official compatible parts and maintenance instructions.
A low charging cost does not establish cleaning performance or product durability. For a purchase decision, compare fit, navigation limits, floor types, recurring supplies, privacy controls and return terms alongside the transparent energy estimate.
Choose your next step
Continue with the question that matches your next decision:
Sources & further reading
Numerical examples are illustrative unless explicitly described as measured. This guide does not claim hands-on product testing. Read the methodology and editorial disclosure.