The rating label helps identify the appliance, but a motor output figure is not automatically its electrical consumption throughout a session. Actual running time and operating conditions also matter.
What the observation tells you
Avoid multiplying an advertised horsepower number directly by an electricity tariff or assuming the disposer consumes its maximum rated value continuously. If an estimate is needed, obtain the relevant electrical input information from the manufacturer and use realistic operating time. Do not insert an unsuitable meter or extension arrangement into a wet cabinet.
A useful next step
Treat the result as an estimate with stated assumptions. An unexplained change in performance should be assessed as a fault rather than dismissed as an energy-cost issue.
Manuals and supporting guidance
Model-specific instructions take priority. These references support the practical principles discussed here; they do not diagnose your appliance.