Build one row per billing period
Record start date, end date, number of days, kWh, variable charges, fixed charges and credits. Note estimated readings and corrections. Use contiguous periods without gaps or overlaps, and keep electricity separate from gas or other billed services.
Where your utility provides downloadable history, preserve the original file and verify its totals against statements. A payment history alone may not represent current consumption charges, particularly under budget billing.
Compare both totals and daily averages
Imagine one 365-day period uses 3,600 kWh and the next 366-day period uses 3,660 kWh. Their daily averages are about 9.86 and 10.00 kWh, respectively. The total increased by 60 kWh, but the extra day explains part of that difference.
At an illustrative flat $0.18/kWh, 3,600 kWh represents $648 in variable electricity cost. That repriced estimate excludes fixed fees and does not reproduce historical spending if rates changed during the year.
Annotate household changes
Mark moves, additional occupants, extended trips, a new home-office routine and equipment replacements. Note whether heating or cooling had an unusually long season. Those observations do not fully normalize weather, but they prevent an overconfident claim that a small annual difference proves one appliance paid for itself.
For a specific improvement, retain a more targeted comparison alongside the annual overview. Whole-home totals can hide a small saving behind a larger change elsewhere.
Keep history and forecast separate
Use actual charges to answer what you spent. Use observed kWh and an explicitly chosen tariff scenario to estimate a future year. A simple flat-rate forecast is a planning approximation if your tariff includes tiers or time-of-use periods. Save the rate date, assumptions and expected household changes. This produces a budget you can update without rewriting the past or mistaking a one-time credit for a permanent reduction in running cost.
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.