How to Calculate Free Electricity Hours Savings

Use Smart Meter Data to Value Free Midday Electricity, Load Shifting, EV and Battery Charging

Last Updated: 2026-09-15

Key Takeaways

To calculate savings from free electricity hours, multiply the grid energy used inside the window by your normal rate minus the window rate.
Subtract any higher rates or higher daily supply charge that the plan adds at other times. A household that moves little use can pay more.
Smart meter data shows how much grid energy you already use inside the window, by day and by season.
Load shifting by appliance timer, electric vehicle (EV), or battery saves about each moved kWh's normal rate minus the window rate, up to any daily cap.
In a solar home, rooftop solar supplies part of midday use first, so free midday electricity applies to less energy.
The same spreadsheet sum is your own solar sharer savings calculator or midday power saver savings estimate. Only the window hours, rates, and cap change.

Calculate Savings from Free Electricity Hours

Governments run free or reduced-rate midday electricity windows in several Australian states, and the savings arithmetic is the same for each. For a general overview of which scheme applies where, see which states have free electricity hours. For a general overview of each scheme, follow its link below.

Solar Sharer Offer: a federal free window in New South Wales, South Australia, and south-east Queensland.
Midday Power Saver: a Victorian Government free window, announced but not yet in effect as at 15 September 2026.
Solar Soak Period: a Victorian reduced-rate band inside a time-of-use (TOU) tariff.

The Formula for Your Own Solar Sharer Savings Calculator

You can do this sum yourself in a spreadsheet. For your current rates, see how to interpret your electricity bill.

Window saving = energy used inside the window (kWh) × (normal rate − window rate).
Extra usage cost = energy used outside the window × any increase in the outside-window rate. Repeat this step for each TOU rate period.
Extra supply cost = any increase in the daily supply charge × the number of days.
Net saving = window saving − extra usage cost − extra supply cost.

Count energy in step 1 only up to any daily cap on free energy. The Solar Sharer Offer and Midday Power Saver each cap free use at 24 kWh a day (subject to confirmation).

Measure Midday Use with Smart Meter Data

Interval Data records grid use in short intervals, commonly every 30 minutes and sometimes every 5 minutes, so it shows the use inside any window.

Download the data: your DNSP and your electricity retailer must both supply Interval Data in the NEM12 CSV Format that AEMO defines. See how to download your smart meter data.
Select the import registers: E1, E2, and E3 are always mains-grid import registers, and E1 is almost always the main register. Count E2 only where the plan applies the window to that Controlled Load.
Mark the window intervals: 11am to 2pm covers six 30-minute intervals, and 11am to 4pm covers ten.
Total each day: sum the window kWh for each day, then average the totals by month and by weekday or weekend.

Try our NEM12 Smart Meter Data Analyzer Tool

For pivot-table steps, see how to analyse NEM12 smart meter data in a spreadsheet. For what each NMI Suffix code means, see how to interpret your smart meter data.

Try our NEM12 CSV Spreadsheet Converter Tool

Value Load Shifting with an Appliance Timer

Load shifting moves electricity use from another time into the window.

Load	How it moves	What limits the saving
Dishwasher, washing machine, clothes dryer	Appliance timer or delay start	Some models have no delay start
Pool pump	Pump timer	A pump that already runs at midday adds no saving
Electric or heat pump hot water	Built-in or electrician-fitted timer	Tank size, and whether it is on a Controlled Load
Pre-heating or pre-cooling	Reverse-cycle air conditioner timer	The heat or cool the home keeps until evening

Controlled Load hot water runs on a Dedicated Circuit with a secondary import register, typically E2, and rooftop solar cannot supply it. It often already pays a discounted Off-Peak rate, so a moved kWh saves less than one moved from an evening Peak.

Charge an EV or Battery During Free Hours

Charge EV During Free Hours

Energy moved: charger power in kW × the hours the car is home and plugged in inside the window, up to the daily cap.
Charger power: a 7 kW charger can deliver up to 21 kWh over three hours. A standard power point, at about 2.4 kW, delivers about 7 kWh.

Charge Battery During Free Hours

Where its settings allow, a home battery can charge from the grid inside the window, up to its capacity and charge power. The battery can then supply that energy to the home in the evening. Each kWh it supplies saves about the evening rate minus the window rate, less charging and discharging losses.

Solar or grid charging: grid charging in the window adds little on days when rooftop solar fills the battery. It is more likely to add value in a cool-climate winter, with less solar surplus.
Warranty terms: daily grid charging adds cycles, so check the warranty terms. For a general overview, see whether to add a battery to existing solar.

How Rooftop Solar Changes the Saving

Energy that rooftop solar supplies at midday does not come from the grid, so a free grid window does not make it cheaper. The smart meter records import on E1, E2, and E3 and export on B1, but it cannot measure self-consumption (the solar used on site).

E1 inside the window: the grid energy the window can make free, which can be close to zero on sunny days.
Loads moved onto solar: a load moved to midday uses surplus solar first, which reduces B1 export and its Solar Feed-in Tariff (FiT) credit. The window adds value only for import above the solar output.
Separate flows: E1 and B1 are two separate physical flows. Never calculate net import as E1 minus B1.

Worked Example of Free Electricity Hours Savings

This example uses illustrative rates for a household without solar (sample NMI 6200000000). The rates describe no real plan.

The Example Household and Plans

Use: 20 kWh a day, with 2 kWh already inside an 11am to 2pm window.
Current plan: a Flat Rate of 30c per kWh.
Free-hours plan: 0c per kWh inside the window, 35c per kWh outside it, and a daily supply charge 10c higher.

Without Load Shifting

Window saving: 2 kWh × (30c − 0c) = 60c a day.
Extra usage cost: 18 kWh × (35c − 30c) = 90c a day.
Extra supply cost: 10c a day.
Net saving: 60c − 90c − 10c = −40c a day, or about −$146 a year.

With 4 kWh a Day Moved by Timers

Window use: 2 kWh + 4 kWh from the dishwasher, washing machine, and heat pump hot water = 6 kWh.
Window saving: 6 kWh × (30c − 0c) = $1.80 a day.
Extra usage cost: 14 kWh × (35c − 30c) = 70c a day.
Extra supply cost: 10c a day.
Net saving: $1.80 − 70c − 10c = $1.00 a day, or about $365 a year.

In this example, the plan costs more without load shifting and saves money with it.

Which Households Gain Most from Free Midday Electricity

Households Likely to Gain More

Home at midday: retired or work-from-home households can run loads in the window on weekdays.
EV at home by day: a car parked at home at midday can use a large share of the cap.
Battery with a winter shortfall: a battery that solar cannot fill can charge from the grid in the window.

Households Likely to Gain Less

Away at midday: most use falls in the evening, where higher rates can apply.
Large rooftop solar: the panels can already cover most midday use.
Low total use: a higher daily supply charge can exceed a small window saving.

Visualise Your Own Free-Hours Usage in Smart Meter Data

To see which group your household is in, total a year of your NEM12 Interval Data inside the window for each season. Then put those totals into the formula above.

Try our NEM12 Smart Meter Data Analyzer Tool

Frequently Asked Questions

How do I calculate savings from free electricity hours? Multiply the grid energy used inside the window by your normal rate minus the window rate. Then subtract any extra cost that the plan adds outside the window or in the daily supply charge.
How do I build my own solar sharer savings calculator? Put your daily grid use inside the Solar Sharer window into a spreadsheet, then apply the formula with the plan's rates and daily cap. Your smart meter data supplies the window totals.
How can I estimate Midday Power Saver savings from my own data? Total your grid import inside the Victorian window for each day, then apply the plan's rates. Check the window hours on the plan before you count the intervals.
What smart meter data do I need to estimate free electricity hours savings? You need a year of Interval Data in NEM12 CSV from your DNSP or electricity retailer. A full year shows how midday use changes between seasons.
Which register shows the energy a free window can make free? E1, almost always the main grid import register, shows it for most homes. E2 counts only where the plan applies the window to that Controlled Load circuit.
What is load shifting? Load shifting moves electricity use from one time of day to another, such as into a free or cheap midday window. Each moved kWh saves its normal rate minus the window rate.
Which appliances can an appliance timer move into free midday electricity hours? A dishwasher, washing machine, clothes dryer, pool pump, or hot water system with a timer can often run inside the window. Some models have no delay-start setting.
Is it worth moving Controlled Load hot water into the free window? Each moved kWh saves less, because Controlled Load hot water often already pays a discounted Off-Peak rate. Rooftop solar also cannot supply that circuit.
How much energy can I charge EV during free hours? The energy is the charger power × the hours the car is plugged in inside the window, up to any daily cap. A 7 kW charger over three hours can deliver up to 21 kWh.
Is it worth it to charge battery during free hours if I have rooftop solar? Grid charging adds little on days when solar already fills the battery. It is more likely to add value in winter, when solar surplus is lower.
Does rooftop solar reduce free midday electricity savings? Yes. Energy that rooftop solar supplies at midday does not come from the grid, so the free window cannot make that energy cheaper.
What do I give up when I move a load onto midday solar? The load uses surplus solar first, which reduces B1 export. You lose the credit from the Solar Feed-in Tariff (FiT) on that energy.
How does a daily cap on free energy affect the saving? You count free energy only up to the cap each day. The Solar Sharer Offer and Midday Power Saver each cap free use at 24 kWh a day (subject to confirmation).
Can a free-hours plan cost more than my current plan? Yes. Higher rates outside the window or a higher daily supply charge can outweigh the window saving for a household that moves little use.
How do I include a higher daily supply charge in the calculation? Multiply the increase in the daily supply charge by the number of days. Subtract that amount from the window saving.
Can I find net import by subtracting B1 from E1? No. E1 and B1 record two separate physical flows, so net import is never E1 minus B1.
Does pre-heating a home in the free window save money? It can save money when it replaces evening heating at a higher rate. To check, compare evening import on pre-heated days with similar days in your smart meter data.
Do free electricity hours savings change between summer and winter? They can. Heating load and rooftop solar output both change with the season, so calculate the window total for each season.
Which households gain most from free midday electricity? Households home at midday, households with an EV parked at home by day, and households with a battery that solar cannot fill tend to gain most.
Which households gain least from free electricity hours? Households away at midday, households with large rooftop solar, and households with low total use tend to gain least.

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Glossary

30-Minute Interval Data: The standard half-hourly resolution at which Australian smart meters record electricity import and export. NEM12 CSV is typically supplied with 30 Minute Intervals.
AEMO: Australian Energy Market Operator — the body that administers the National Electricity Market and defines and maintains the NEM12 specification.
B1: In the NEM12 Format, the Meter Register code for Solar Export — electricity generated on site and fed back to the grid, typically measured in kWh.
Check Digit: The 11th digit of a full NMI — calculated from the first ten digits to detect transcription errors; some DNSP portals require it. Also called a 'Checksum'.
Controlled Load: A separately metered circuit controlled by a signal from the DNSP. These circuits typically contain a single specific appliance or type of appliance - eg. an Electric Hot Water Service (and historically Air-Conditioners or Electric Slab Heating). They are typically billed at a discounted rate and often run only during off-peak hours. They appear on a separate Meter Register on an Electricity Bill. See also: Dedicated Circuit.
CSV: Comma-Separated Values — a plain text file in which each row is a record and fields are separated by commas.
Daily Cap: The maximum amount of energy, in kWh, that a plan supplies free or at the reduced rate inside its midday window each day. Energy above the cap is charged at the rate the plan terms set.
Daily Supply Charge: The fixed amount an electricity or gas plan charges for each day a property is connected to the network, whatever amount of energy the household uses. Also called a Daily Connection Charge.
Dedicated Circuit: The physical wiring and breaker serving a Controlled Load device, isolated so the DNSP can independently control supply. See also: Controlled Load.
DNSP: Distribution Network Service Provider - the company that owns and operates the physical poles and wires of the local electricity network, and usually provides the smart meter data portal. Not the same as your Electricity Retailer. See also: Electricity Retailer.
E1: In the NEM12 Format, the Meter Register code (or NMI Suffix) for the sole/main/primary mains grid import channel — electricity drawn from the network. Where there is No (Solar) Generation on site, this is the Total Consumption. Typically measured in kWh.
E2: In the NEM12 Format, the Meter Register code (or NMI Suffix) for a secondary mains grid import channel — typically controlled-load or off-peak consumption such as dedicated hot water. Present only where that tariff exists.
Electricity Retailer: The company that sells electricity to the consumer, issues the bill, and manages the account. Not the same as your DNSP (Distribution Network Service Provider) which owns and operates the network. See also: DNSP.
Flat Rate: A single price per kWh that applies at all times of day (and all days of the week). Also called Single Rate.
Free Electricity Window: A daily block of hours, usually around midday, when grid electricity on a plan is free or charged at a reduced rate.
Interval Data: Energy readings recorded at fixed time steps — typically every 30 minutes (but sometimes 5 or 15 minutes on newer meters) rather than as a single billing total. This allows charging different Tariffs at different times of day or days of the week. See also: Time-of-Use (TOU) Tariff.
kW: KiloWatt — the standard unit of (Electrical) Power: 1,000 Watts of Power used continuously for one hour is equivalent to 1000 Watt-Hours or 1 KiloWatt-Hour of Energy. Power is not an Amount of Energy but a Rate of Energy Transfer. See also: kWh.
kWh: KiloWatt-Hour — the standard unit of (Electrical) Energy: 1,000 Watts of Power used continuously for one hour is equivalent to 1000 Watt-Hours or 1 KiloWatt-Hour. NEM12 CSV records Electricity Use in kWh. See also: kW.
Load Shifting: Moving discretionary electricity use, such as a dishwasher or an EV charge, to a chosen time of day — usually out of a peak tariff and into an off-peak tariff or sunniest solar generation hours — using timers, schedules, or habit.
NEM: The Australian National Electricity Market — the interconnected electricity grid covering Queensland, New South Wales, Victoria, South Australia, Tasmania and the ACT. Western Australia and the Northern Territory operate separate grids.
NEM12: The AEMO file format (version 12) for exchanging Interval Data from Smart Meters across the Australian National Electricity Market (NEM). NEM12 Format records the Amount of Energy per Time Interval in kWh. And also other types of data, using specific types of labelled rows or records (100, 200, 300, 400, 900) to record different types of data. This makes it a 'Semi-Structured' 'Non-Tabular' Format. See also: AEMO, NEM, kWh, Semi-Structured, Non-Tabular.
NEM12 CSV: A NEM12 File stored as comma-separated values — the form most DNSP and retailer portals distribute. See also: NEM12, CSV.
NEM12 CSV Format: See NEM12 CSV.
NMI: National Metering Identifier — the unique 10-digit identifier for an electricity connection point (11 with the Check Digit), permanent to the property. Note that the electricity connection point identified by the NMI, typically has multiple NMI Suffixes, and can have multiple Physical Meters. See also: Check Digit, NMI Suffix.
NMI Suffix: In the NEM12 Format, the short two-character code (E1, E2, E3, B1, B2, Q1, K1) identifying a specific Meter Register for recording electricity flows on the mains electricity connection identified by that NMI — also called the Meter Register or Register Code. See also: NMI, NEM12.
Non-Tabular: Data that does not fit a single consistent grid — in NEM12's case because of its semi-structure, hierarchy and mixed-record layout.
Off-Peak: The lowest-priced time period in a Time-of-Use (TOU) Tariff — typically overnight and sometimes weekends. In current usage refers to the Time electricity is imported on a Meter Register and at Other Times, the import rate on that Same Meter Register might be different. It can also currently refer to Dedicated Circuits / Controlled Loads that are only permitted to draw power at set Off-Peak times. And historically, before Smart Meters, only the latter could receive an Off-Peak Rate. See also: Time-of-Use (TOU) Tariff, Controlled Load, Dedicated Circuit.
Peak: The highest-priced time period in a Time-of-Use (TOU) Tariff — typically weekday daytime and early evening. See also: Time-of-Use (TOU) Tariff.
Self-Consumption: The share of the electricity generated by your own solar panels that your household uses on site, rather than exporting it to the grid.
Semi-Structured: A data format that follows strict syntactic rules (e.g. comma separation, defined record codes) but does not enforce a consistent column schema across all rows. NEM12 is a Semi-Structured Format. See also: NEM12.
Smart Meter Data: Electricity import and export readings recorded by a digital interval meter at regular intervals. In Australia, typically supplied in NEM12 CSV Format with 30 Minute Intervals. See also: NEM12 CSV.
Solar Feed-in Tariff (FiT): The credit paid (in cents per kWh) by your Electricity Retailer for solar electricity you export to the grid (B1 Meter Register). In Victoria, a minimum rate was historically set annually by the Essential Services Commission (ESC). However, since July 2025, the ESC no longer sets a minimum, and Electricity Retailers are free to pay a Market Rate.
Time-of-Use (TOU) Tariff: A tariff with different prices at different times of day or days of the week (Peak, Shoulder, Off-Peak).
TOU: See Time-of-Use (TOU) Tariff.

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