'On/off' solar curtailment - who it applies to and how it works

What is on/off curtailment?

One of the issues affecting solar homes across Australia in 2023 is negative feed-in tariffs for solar exports at times. FiTs turning negative is a price signal from the energy market that there’s a lot of renewable energy in the grid in the middle of the day, and not enough demand for it (people to use it at that time). When there’s more renewable energy trying to enter the grid than is needed at that time, negative feed in tariffs mean you get charged to export. 

There are a number of steps we’re taking to limit the impact of negative FiT for our customers - and there’s a bunch of ways you can increase your chances of ending up better off too. 

Solar curtailment is one of these options. It involves Amber limiting the solar energy you produce during periods when FiTs turn negative, to restrict the amount you export at these times. 

Who does on/off curtailment apply to?

On/off curtailment is available in the case that you have:

• Multiple Sungrow inverters
• One Sungrow inverter AND an inverter from another brand
• A Fronius inverter without a consumption meter (otherwise known as Fronius smart meter)
• An AC-coupled battery (eg Tesla, AlphaESS) paired with a Sungrow or Fronius inverter, without a consumption meter

If you have a solar inverter we can control, please enrol it via the 'Devices' tab in you Amber app. If you're already on SmartShift with your battery, enrol another device is found under 'SmartShift Settings'

As of October 2023, all new incoming SmartShift customers who have this set up will have on/off curtailment auto-enabled as soon as they onboard. 

(Alternatively, if you have a DC-coupled system listed here, you can take advantage of Load-Following Curtailment once your system is configured. Learn more about Load Following Curtailment)

How does on/off curtailment work?

If you have a setup that supports on/off curtailment, SmartShift may stop your solar production completely during periods of negative FiT. SmartShift will consider the house’s energy use (if it is available), the cost to export and the cost to buy from grid, and choose the cheapest option.

In effect, what this means is that:

• If you’re not using much energy in your home at this time, SmartShift will direct your panels to curtail (generate zero energy) and you’ll pull from the grid instead to run your home. Given that this is occurring because FiT is negative, you can be confident that your usage costs from drawing from the grid will be extremely low. 
• If you're using lots of energy at this time and SmartShift determines it would be cheaper to use your own solar, SmartShift will direct your panels to generate energy so you can benefit from using that no-cost solar to meet your energy needs. However, any excess that you can't consume at this time will go to the grid. 

SmartShift will review the status of your house's energy consumption levels every five minutes to determine whether it makes sense to curtail or allow your panels to generate energy for your home. 

Note: This curtailment will begin only once your battery is fully charged. When the wholesale grid price is <0c/kWh you will be getting paid to use power.

What if I don't have a battery?

If you don't have a battery SmartShift does not know much energy is being used in your home at any given time, so when prices are negative your inverter will be directed to turn off. 

You can disable curtailment in the Amber app at any time to turn your inverter back on. 

To learn more about negative feed-in tariffs and why they occur, head here. 

NOTE FOR SUNGROW HYBRID SOLAR SYSTEM OWNERS IN THE EVENT OF AN OUTAGE:

For Sungrow hybrid solar systems configured for on/off curtailment, we send a command to the solar and battery system to temporarily shut down when the cost to draw from grid is lower than the cost to export their solar (i.e. the FiT is negative).

However, if a grid outage occurs when the Feed-in Tariff is negative, and the last command received by the system was to shut down, then the system doesn’t know that there’s an outage and will not shift into backup mode.

In order to solve this:

• If/when an outage occurs, disable SmartShift Automation in the Amber App (Devices tab - Settings)
• Follow Sungrow reboot procedure (video here)
• Turn on optimisations again when the grid electricity outage is over.