Use input watts, not suction language
The bill reflects electrical energy drawn from the outlet. Air watts, pascals and other suction descriptions address performance in different ways and should not be entered as electrical watts unless the documentation explicitly identifies them as input power.
Find rated input on the product label or manual. For variable-power equipment, measure a representative whole cleaning session with suitable equipment rather than relying on the highest mode alone.
For cordless models, the charger’s wall energy across a complete recharge is the relevant bill input. Battery voltage and amp-hours can describe stored energy, but multiplying them does not account for charging losses or dock standby on its own.
Convert minutes into hours
A 1,000 W input is 1 kW. Thirty minutes is 0.5 hour, so the session uses 1 × 0.5 = 0.5 kWh and costs $0.09 at $0.18/kWh. Four such sessions cost $0.36.
A 700 W vacuum used for 45 minutes consumes 0.525 kWh, costing about $0.09 at the same rate. The lower wattage does not guarantee a lower session cost if cleaning takes longer.
For monthly planning, count realistic sessions rather than assuming daily use. Note whether stairs, furniture attachments or maximum mode add time. The best comparison keeps the floor area and acceptable cleaning result similar instead of rewarding a shorter but incomplete task.
Compare a complete cleaning task
To compare two machines, measure the same suitable area and note passes, power mode and time. One short spot-cleaning result should not be presented as a whole-apartment average. Battery vacuums should be measured at the charger across complete recharge cycles.
Do not double-count battery capacity and wall charging energy. If the meter reports wall kWh, that figure already includes conversion and charging losses for the observed cycle.
Keep maintenance and performance visible
Filters, bags, brush condition and blockages can affect usefulness and the time needed to finish. Follow the manufacturer’s maintenance directions instead of assuming a wattage change proves efficiency.
For buying decisions, electricity may be small compared with the purchase price and replacement parts. Compare the cost of completing the task, not just one large number printed on the box.
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.