Is the meter data file uploaded or saved?

No. The file is read by your browser on this page and never sent to Wattbench. The tool has no Save result, the file and its readings never go into browser storage or the address bar, and reloading or leaving the page discards them. Opening a calculator from the results passes only the figures it fills, through this tab's session storage, and the calculator deletes them as it reads them. The NMI is shown only by its last four characters and is never shared or handed on.

Which channels are counted?

E channels are grid import (energy drawn from the grid) and B channels are grid export, as AEMO's NMI Procedure defines the suffixes from the market's side. Any other suffix, or an E or B channel not in Wh, kWh or MWh, is shown as not classified and left out of the totals.

Is the peak the customer's maximum demand?

It is the highest interval-average kW: the interval's kWh × 60 ÷ its length in minutes. Instantaneous demand inside that interval can be higher, and it is not a per-phase current, so it is not a figure for sizing a supply or protection.

Why is daily import lower than the household's use on a solar site?

The meter records energy drawn from the grid. On a site that already has solar, energy that system supplied directly never passes through the meter, so it is not in the file.

How are estimated or substituted readings handled?

They are included in the figures and counted by quality flag: actual, substituted, final substituted, forward estimated, or other or missing. The share of readings that are not actual is shown, so you can judge how much of the history was measured.

How large a file can it read?

Up to 20 MB. A year of 5-minute data is read in slices, so the page stays responsive while it works.

Measured Load

NEM12 Interval Data Load Profiler

Read a customer's NEM12 meter data file in your browser for daily grid import, kWh in your own time windows, peak interval-average demand, an average day and export totals.

Sources listedReviewed September 2026Our methodology

NEM12 interval data file (.csv)One NEM12 file, up to 20 MB. It is read in this browser and never uploaded or saved; reloading or leaving the page discards it.

Time windows

kWh inside each window, in 30-minute steps. An end at or before the start runs across midnight.

Window 1 start

Window 1 end

Choose a NEM12 file to see daily import, your time windows, peak interval-average demand, the average day and export, all measured from the file.

Key takeaways

Reads the NEM12 file in your browser: nothing is uploaded or saved, and the NMI is shown only by its last four characters.
Takes each channel's interval length from its 200 record and honours the quality flags in its 300 and 400 records, counting substituted, final substituted and estimated readings.
Reports daily grid import, kWh inside time windows you set (including across midnight), an hour-by-hour average day and export totals.
The peak is the interval-average kW of each channel's highest interval, not instantaneous demand and not a per-phase current.
Hands the measured figures to the battery and system size calculators, labelled with the file's date range. Measured history, not a forecast.

How it works

The file is read against AEMO's Meter Data File Format Specification NEM12 & NEM13. The first record must be a 100 header naming NEM12; a NEM13 file (accumulated readings) or any other CSV is turned away with a message, not guessed at.

Interval length. Each 200 record states its own IntervalLength of 5, 15 or 30 minutes, and each 300 record must carry exactly 1440 ÷ IntervalLength readings. Nothing is assumed: a block with any other length is skipped and counted.
Channels. AEMO's NMI Procedure names energy flows from the market's side, so an E suffix (“export kWh” to AEMO) is energy the site draws from the grid and a B suffix (“import kWh”) is energy it sends to the grid. Any other suffix, or an E or B channel not in Wh, kWh or MWh, is shown as not classified and left out of every total.
Quality. The 300 record's QualityMethod applies to the whole day unless it is V, when the 400 records give each interval range its own flag. Readings are counted as actual, substituted, final substituted, forward estimated, or other or missing, and the share that is not actual is shown.
Daily figures. A day counts when every import and export channel has a reading for it, so the mean, median, lowest and highest day, the windows and the average day all cover the same days.
Time windows. An interval counts toward a window when it starts inside it. Windows move in 30-minute steps, which fall on an interval boundary for 5-, 15- and 30-minute data alike, and an end at or before the start runs across midnight.
Peak. The interval-average kW, kW = interval kWh × 60 ÷ interval minutes, the highest per channel. It is the average across one interval, not instantaneous demand and not a per-phase current.

Grid import is what passed through the meter. On a site that already has solar it leaves out the energy that system supplied directly, so the self-consumed share is not in the file. The figures can open the battery size calculator or the system size calculator with their fields filled and labelled; the time windows help line load up against a time-of-use tariff. Files up to 20 MB are read in slices, so a year of 5-minute data does not lock the page.

Measured history from the meter data file you choose, not a forecast, a quote or a compliance certificate. The file is read in your browser and never uploaded; this tool has no Save result, and the NMI is shown only by its last four characters.

Source ledger2 sources

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Frequently asked

Is the meter data file uploaded or saved?: No. The file is read by your browser on this page and never sent to Wattbench. The tool has no Save result, the file and its readings never go into browser storage or the address bar, and reloading or leaving the page discards them. Opening a calculator from the results passes only the figures it fills, through this tab's session storage, and the calculator deletes them as it reads them. The NMI is shown only by its last four characters and is never shared or handed on.
Which channels are counted?: E channels are grid import (energy drawn from the grid) and B channels are grid export, as AEMO's NMI Procedure defines the suffixes from the market's side. Any other suffix, or an E or B channel not in Wh, kWh or MWh, is shown as not classified and left out of the totals.
Is the peak the customer's maximum demand?: It is the highest interval-average kW: the interval's kWh × 60 ÷ its length in minutes. Instantaneous demand inside that interval can be higher, and it is not a per-phase current, so it is not a figure for sizing a supply or protection.
Why is daily import lower than the household's use on a solar site?: The meter records energy drawn from the grid. On a site that already has solar, energy that system supplied directly never passes through the meter, so it is not in the file.
How are estimated or substituted readings handled?: They are included in the figures and counted by quality flag: actual, substituted, final substituted, forward estimated, or other or missing. The share of readings that are not actual is shown, so you can judge how much of the history was measured.
How large a file can it read?: Up to 20 MB. A year of 5-minute data is read in slices, so the page stays responsive while it works.