Which electricity price should I use when calculating wind power savings?

The short answer

Use the charges the project can actually avoid, evaluated at the relevant times. Dividing the entire bill by total kWh can include fixed and demand charges that wind may not reduce. Exported energy may receive a different value again. Start with the actual tariff and a load-generation balance, then calculate the bill with and without the wind project.

Separate the bill components

Identify energy charges, demand-related charges, fixed charges, taxes and any other items that apply. Determine which items change with imported kWh, which depend on a billing peak and which remain payable. Time-of-use energy prices require matching generation to the appropriate periods.

A first screening estimate can use an explicitly assumed marginal energy value, but it should not be labeled a complete bill-saving forecast. The final comparison needs the actual applicable contract and billing rules.

Test the average-price shortcut

Hypothetical monthly bill: 5,000 kWh at 0.20 currency units/kWh costs 1,000. Add 200 of fixed charges and 300 of demand charges, giving a total of 1,500. The average bill divided by energy is 0.30/kWh.

If wind offsets 1,000 kWh while leaving the demand and fixed charges unchanged, the energy saving is 200, not 300. Applying the all-in average would overstate this simplified saving by 50%. The assumed rates are not a current tariff or a MARSTON economic promise.

Build a realistic value range

Use separate values for self-consumed and exported electricity, and account for imports required by the wind system if they sit outside the chosen boundary. Where rates or operating schedules may change, show more than one case rather than hiding the change inside a blended number.

The rate assumption should be easy to trace to a bill, tariff document or stated scenario. Keep demand-charge benefits separate until interval analysis supports them. This helps distinguish a site with valuable wind generation from one that merely has a high-looking average electricity bill.