Start with actual consumption and timing. Money spent alone can hide changes in prices, weather and household routine.
Build a simple baseline
Collect a full year of readings where possible and distinguish actual readings from estimates. Record electricity in kWh separately from other fuels. Note changes such as a new occupant, electric vehicle or a period when the home was empty.
Find patterns rather than blame
If your meter provides interval data, compare overnight use, working days and weekends. Look for sustained patterns before buying monitoring hardware. A single unusually high day may reflect a special event, not a persistent problem.
Change one thing and observe
Choose a practical adjustment, record when it starts and compare similar periods. Weather and occupancy can affect the result, so resist assigning every change to one device. Use appliance instructions and preserve ventilation, comfort and safe operating conditions.