Master Subtractive Metering Rectification

Looking at a meter

What is a Master Subtractive Meter?

A master-subtractive meter arrangement is a way of measuring your property’s electricity usage that’s no longer in use. It involves a ‘master’ meter at the point where electricity enters the property or properties, and subtractive meters further along the network. Subtractive meters are typically used to measure the usage of hot water systems, under floor heating, water pumps and sheds.

If you have a master/subtractive metering arrangement, your electricity usage is determined by deducting the reading on your subtractive meter from the reading on the master meter. The net figure is used by your retailer to calculate your energy bill.

Master sub metering diagram

What has changed in relation to Master Subtractive Metering configurations?

Under 2017 changes to the Australian Energy Market Operator rules, all electricity meters must display the actual meter reading for that premises. This means that Master Subtractive Meter arrangements are no longer permitted and must be replaced.

What is Essential Energy doing about the 2017 rule change?

Essential Energy is working to ensure all non-compliant master/subtractive meters are compliant with the 2017 ruling as soon as possible. The works required to correct the arrangement will be assessed on a case-by-case basis as the arrangement at each property is unique.

What do I need to do?

If your property has a master subtractive metering arrangement and needs to be corrected, we will contact you in writing.

Generally, the process to change your metering arrangement will follow the steps below:

  1. Essential Energy will write to you to inform you that you have a master subtractive metering arrangement that needs to be corrected, and to arrange a date to inspect your property to help determine the works required.
  2. Essential Energy will develop a method to correct your metering configuration and communicate that plan with you. If your premise is occupied under a lease arrangement, the owner of the premise will also be contacted.
  3. Works to change your metering configuration will be completed.
  4. Following completion of the works, Essential Energy will notify your retailer that your metering configuration has changed.

How will I know if my meter needs to be replaced?

Essential Energy has commenced contacting customers with a master subtractive metering configuration. Once we get in touch, Essential Energy will arrange for the site to be reviewed and the rectification works to be completed. The rectification solution will be determined on a case-by-case basis. Essential Energy has a dedicated customer liaison team for the master subtractive metering program to help customers through all aspects of the process. They can be contacted on 0265898830 or

Will I have to pay for the rectification works?

Essential Energy will fund the most suitable solution to rectify the non-compliant metering configuration. We will discuss and agree the scope of works with you before proceeding to construction.

Do I need to be onsite while the works are happening?

You do not need to be onsite for the initial consultation or when the rectification works are carried out. However, Essential Energy does require safe access to your property. You can help by leaving entry gates and meter boxes unlocked and securing dogs and livestock. If you are onsite, Essential Energy employees will maintain social distancing, in line with COVID-19 response recommendations.

How long will the process take?

Essential Energy is committed to working with customers to ensure the rectification of their master subtractive metering configuration is as simple as possible. The length of the process will be different for each site dependent on the works required.

If my meter has failed, how will I be billed?

Customers with a failed meter will receive a bill that is based on an estimated reading. Essential Energy reviews estimated bills manually before they are sent.

Can I opt out of the rectification?

Essential Energy will work with each customer to find the best rectification solution for their site. All MSM sites must be rectified to be compliant with the Australian Energy Market Operator rules.

Will there be any power outages or interruptions?

Essential Energy is committed to working with customers to ensure the rectification of their master subtractive metering configuration is as simple as possible. As with most works on the network in and around residential homes, Essential Energy will need to arrange a power outage to enable the work onsite to be carried out safely and we will be in touch with details well in advance of the outage occurring.

My meter has not failed. Do I need to do anything?

All master subtractive metering configurations need to be rectified to be compliant with the Australian Energy Market Operator rules. Essential Energy will prioritise the rectification of failed meter sites, and then commence rectifying other master subtractive metering sites. If your property has a master subtractive metering configuration and needs to be corrected, we will contact you in writing.

What options will I have for the rectification of my MSM configuration?

Essential Energy determines rectification solutions on a case-by-case basis. Our dedicated master subtractive metering customer liaison team will help you through all aspects of the process. In many cases, the simplest and most suitable solution involves removing your subtractive meters, replacing your master meter with a new Smart Meter and a time clock for off peak appliances and placing you on a Time of Use (TOU) tariff. You can learn more about TOU here. If you have any questions about the change-over process or your rectification options, our team can be contacted on 0265898830 or

What are the benefits of having a Smart Meter installed?

Advanced, or ‘smart’ digital meters with remote communications hardware can provide you with greater access to energy consumption information, and your electricity retailer with remote meter reading, connection and disconnection capability. Smart Meters are also compatible with new technologies including solar and battery storage, enabling electricity retailers to offer you innovative products and services.

If you have any further enquiries please contact us on 0265898830.