Put a cost on one source of waste
Leaving it on once may cost little.
Leaving it on every night is another story.
Suppose an unnecessary 2 kW load runs for an extra 12 hours on 20 days each month, at an assumed electricity rate of CNY 1 per kWh.
If that operation is genuinely unnecessary and you eliminate it, you can reduce the associated consumption costs. The meter does not save energy by itself; it helps you find where to act.
Illustration using Chinese yuan and an assumed rate, not customer data or a savings guarantee. Changes to fixed charges are excluded; essential loads are not treated as waste.
Illustrative calculation / Avoidable extra consumption
2 kW × 12 hours × 20 days
480 kWh / month
480 kWh × CNY 1 / kWh
CNY 480 / month
Use your own equipment power, unnecessary run time and tariff to estimate the opportunity at your premises.