The formula
Total cost = energy used × price per kWh + days × daily fixed charge.
A worked example
300 kWh × 0.25 + 30 days × 0 = 75.00 in your selected currency.
What this estimate includes
Use the same billing period for your energy consumption and day count. Include tax in your tariff if you want a tax-inclusive estimate. Demand charges, tiered rates and one-off fees are not modeled.
Common questions
Where do I find my electricity rate?
Look for the unit rate on your bill or tariff agreement. Convert cents or pence to currency units first: 25 cents is 0.25, not 25.
Can I use this in Europe or North America?
Yes. Enter your local tariff and select EUR, GBP, USD or CAD. Currency selection changes the label only; it does not convert rates.
Further reading
US Energy Information Administration: measuring electricity. Background reference; these tools are independent and are not endorsed by the source organization.