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Solutions / Engineering guide
Wind Power Self-Consumption & Self-Sufficiency Metrics
Two useful local-energy ratios can describe different results from the same wind project. State which wind energy is used by the named loads, then keep generation and consumption as separate denominators rather than treating either percentage as a supply guarantee.
The numerator can match while the denominators differ.
Self-consumption describes use of the defined wind generation. Self-sufficiency describes the share of the defined load supplied by that wind contribution. Both need a period, boundary and accounting method.
01 / Metric definitions
Write the numerator and denominator beside each result.
For a stated period and boundary, define wind self-consumption as wind energy used by the named local loads divided by the relevant wind generation.
For a stated period and boundary, define wind self-consumption as wind energy used by the named local loads divided by the relevant wind generation. Define wind self-sufficiency as that load-serving contribution divided by the total energy consumed by the same loads. Where a denominator is zero, report the ratio as not applicable under the stated convention; undefined arithmetic should not silently become 0% or 100%.
IEA PVPS distinguishes these denominator concepts in solar-generation accounting. The definitions here concern an explicitly identified wind-energy ledger, not adoption of the report’s PV policies or commercial assumptions. State which devices, auxiliary loads and delivery point are included before reporting a percentage.
02 / Aligned intervals
Preserve when generation and consumption occur.
Use generation and load records covering the same intervals, with common timestamps and measurement boundaries.
Use generation and load records covering the same intervals, with common timestamps and measurement boundaries. Identify direct use, imports, exports and other energy paths actually represented by the system. A yearly generation total cannot establish how much coincided with local demand.
If estimates replace records, retain the curve, resource and demand assumptions and the chosen resolution. Coarse interval matching can hide changes within an interval. Avoid presenting matched annual totals as direct consumption or treating an unresolved time convention as measured simultaneous use.
03 / Arithmetic example
Show the difference with an explicitly hypothetical ledger.
Illustrative accounting only: suppose two intervals have 4 and 2 kWh of wind generation, and 1 and 4 kWh of load energy.
Illustrative accounting only: suppose two intervals have 4 and 2 kWh of wind generation, and 1 and 4 kWh of load energy. Assume the already-established direct wind contribution is 1 and 2 kWh, with no storage. Totals are 6 kWh generated, 5 kWh consumed and 3 kWh used locally.
Wind self-consumption is therefore 3 / 6 = 50%, while wind self-sufficiency is 3 / 5 = 60%. The remainder is 3 kWh of generation outside that direct contribution and 2 kWh of load needing another source. These invented quantities are not MARSTON output, an annual forecast or a billing result.
04 / Storage allocation
Define what is counted when energy moves between periods.
If third-party storage is included, identify charging sources, discharged energy and losses with their measurement points.
If third-party storage is included, identify charging sources, discharged energy and losses with their measurement points. Establish how wind-origin energy is attributed when storage can also charge from the grid or another source. Keep direct use and later delivered wind contribution separate.
Do not count battery charging and its later discharge as two deliveries to the same load. Define the opening and closing stored-energy conditions for the reporting period. No storage capability or universal compatibility is claimed here; the proposed configuration needs the applicable supplier evidence.
05 / Operating limits
Keep exports, restrictions and continuity outside the ratio label.
Record the actual treatment of surplus, export restrictions and any curtailed generation.
Record the actual treatment of surplus, export restrictions and any curtailed generation. A statement that generation was not exported does not prove it was usefully consumed: it may have been restricted, lost or sent to another defined destination. The ledger must distinguish those paths.
A high self-consumption ratio can accompany a small contribution to a large load. Even high period coverage does not establish every moment’s supply. Use the export-limit review and separate continuity assessment rather than infer control or backup functions from a percentage.
06 / Comparison record
Report absolute energy and both definitions together.
Provide the period, boundary, data resolution, generation total, local wind contribution, load total and the resulting ratios.
Provide the period, boundary, data resolution, generation total, local wind contribution, load total and the resulting ratios. Include exports, remaining demand and unresolved allocation assumptions. Keep observed results, modelled cases and hypothetical examples visibly different.
For a MARSTON enquiry, send the aligned resource or generation and load information with the proposed equipment and output boundary. Compare candidates against the same definitions. No self-consumption target, fixed bill saving, autonomous operation or guaranteed site-coverage percentage is established here.
Continue the review with Electricity Bills: Inputs for a Wind Project Assessment.
Continue the review with Wind Power Export Limits & Zero-Export Requirements.
Continue the review with AC & DC Coupling for Wind Hybrid Systems.
General background: IEA PVPS: distinct self-consumption and self-sufficiency definitions. These references explain industry concepts; they are separate from the applicable MARSTON product and project documents.
Prepare the information for this review.
Use the checklist to organise the project information. Mark unavailable items and retain document references.
| Review item | Information to provide | Purpose |
|---|---|---|
| Energy definitions | Named loads, wind-generation boundary and reporting period | Fix both denominators. |
| Interval record | Aligned times, units, resolution and quality | Identify coincident contribution. |
| Allocation ledger | Direct use, imports, exports, restrictions and losses | Keep destinations distinct. |
| Storage scope | Charging sources, delivered attribution and opening/closing state | Avoid double counting. |
| Result record | Absolute kWh, both ratios and explicit assumptions | Compare interpretable results. |
Engineering questions.
Are self-consumption and self-sufficiency the same?
No. Their generation and load denominators differ, even when the numerator is the same local wind contribution.
Does equal annual wind generation and demand establish self-sufficiency?
Not by itself. Timing, accepted contribution, restrictions and remaining supply needs must be assessed.
Do the 50% and 60% examples describe MARSTON performance?
No. They are arithmetic results from an explicitly hypothetical energy ledger.
Does zero export prove all wind energy was used?
No. Identify restrictions, losses and other destinations instead of treating every unexported kWh as useful load supply.
Can battery charging and discharge both count as load supply?
Define the accounting method and avoid counting the same delivered contribution twice.
What should accompany a percentage?
Its definition, period, boundary, absolute energy quantities, resolution and unresolved assumptions.
Technical enquiry
Bring your project information to the discussion.
Two useful local-energy ratios can describe different results from the same wind project. Share the available information and the equipment scope you want reviewed in a technical quotation.