{
 "id": "mcs_generation_method",
 "name": "How MCS estimates a system's annual output",
 "category": "payback",
 "value_num": null,
 "display": "Annual output in kWh = system size in kWp x the zone's kWh per kWp figure x a shade factor, which is 1.00 where nothing shades the roof",
 "unit": "formula, MIS 3002 Issue 5.0 Appendix B, the estimate every MCS installer must give in writing before contract",
 "period_start": "2023-05-10",
 "period_end": null,
 "period_kind": "page_date",
 "deadline": null,
 "source_url": "https://mcscertified.com/wp-content/uploads/2025/02/MIS-3002_Solar-PV-Systems-V5.0-Final-for-publication.pdf",
 "source_org": "MCS",
 "checked_at": "2026-09-08",
 "recheck_by": "2027-03-08",
 "history": [],
 "public_note": "This is the sum every MCS-certified installer has to give you in writing before you sign, and the standard says it must come with a warning that output \"is impossible to predict with certainty\". We use the same sum, with the shade factor at 1.00, which is the standard's own value for a roof with nothing in the way.",
 "next": null,
 "url": "https://hearthsum.co.uk/api/mcs_generation_method.json"
}