Use measured power at the wall. CPU TDP and graphics-card power ratings are not measurements of a complete PC’s electricity consumption.
Method and limits
Find the energy charge and currency on your own bill. This tool does not provide a regional tariff. Enter zero deliberately if you are evaluating a zero marginal energy charge; an empty rate is not treated as free electricity.
Formula: watts × daily hours ÷ 1,000 = kWh per day. Multiply by the entered rate. The 30-day and 365-day totals assume the same usage every day. Fixed connection charges, tax and tiered tariffs are excluded unless you account for them yourself.
For a PC with different idle and gaming power, calculate each period separately and add the results. A measured average is more useful than assuming the power supply’s maximum rating is its normal consumption. Include the monitor only if your meter measured it too.