5.4: readings should be at least as frequent as billing and at least quarterly. Gaps at the start or end may be closed with manual meter readings (evidenced by a time-stamped photo of the meter face) treated as taken on the first or last day of the billing period, a practice NABERS has flagged will be restricted in a future update. Gaps inside the period with valid readings on both sides are calculated exactly (for gas, reading difference times the correction factor, from the estimated bill, adjacent bills or the utility in that order, times the heating value, from the utility, the period's bills, or the state default of 37.5 to 40 MJ per cubic metre) and are acceptable data. Unresolvable gaps are interpolated from adjacent bills' daily averages and added in full to the potential error; extrapolation is never allowed and a building without a continuous 12 months cannot be rated. Estimated remote-read interval bills need the utility's written confirmation and weekday interpolation of missing days, added to potential error.
The graph holds this control, the 0 it maps to, and the evidence behind each claim, over MCP and REST.