Managing times when wholesale FiT turns negative

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This FAQ covers:

1. Why FiTs can turn negative 

2. How Amber for Batteries optimises your battery to take negative pricing into consideration

3. How we’re working to enable solar curtailment during periods of negative FiT

4. How we’re incentivising loadshifting to maximise solar usage 

 

1. Why FiTs can turn negative 

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. 

Currently negative FiT occurs most frequently in regions where there is a particularly high proportion of renewable energy in the grid, and during sunny, spring and summer periods in other states. 

The reality is that the wholesale price of energy dipping below zero on occasion is a curious symptom of the success Australia has had in adopting rooftop solar. While in most of the world, the energy transition is at a point where the market will take as much renewable power as you can give it, we are reaching the next stage of the transition - where the problem is often not the supply of renewables, but demand at the times when they’re being generated. 

That’s part of the reason Amber was created - to help more people shift demand to these times and to help more people store and shift the availability of renewable energy to times when people traditionally use more of it (see: Amber for Batteries and EVs). 

As renewable oversupply during mid-day periods becomes a more frequent challenge for solar homes and the grid, restricting the export of solar energy to the grid is now in demand and there’s a game of catch up going on across the industry.

Amber is excited about the role we can all play in managing this period of our energy transition, and we’re proud of the progress made so far. After all, the “future” we are living in here in Australia, where occasional oversupply of renewable energy now happens, is a reality that will become true world-wide eventually. 

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. 

 

2. How Amber for Batteries optimises your battery to take negative pricing into consideration

On days where SmartShift can tell (based on the forecasted wholesale price and your forecasted solar generation for the day) that it’s possible you may end up exporting excess solar during a negative price period, SmartShift will act in advance to reduce the likelihood that this will happen. 

This will typically involve energy being automatically exported from your battery to the grid at a lower wholesale rate earlier in the day to ensure your solar generation can be directed straight to your battery later in the day when the wholesale price dips below zero. So although it may look strange that your stored energy is being exported at a lower rate, this benefits you in the long run by making room for more solar in the battery. 

SmartShift is also always looking for this opportunity to make the most value for our customers and there is no better time to charge up your battery than when the wholesale rate is <0c/kWh. Both the Battery Booster and Earnings Optimiser modes will look to take advantage of these times to charge your battery if it has spare capacity, so you’re topped up with cheap, green energy. 

Beyond this, we’re improving our algorithm and forecasting accuracy, so that SmartShift gets even better at determining how your battery can best be optimised to deliver you more value overall. Stay tuned for more on this exciting work (with the support of CSIRO) in the not too distant future!

The good news is that even though the experience of exporting at Negative FiT can be a frustrating one, Amber’s data shows that most Amber for Batteries customers came out on top with wholesale FiTs over the past 12 months, despite sometimes exporting during negative FiT periods. 

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3. Solar curtailment during periods of negative FiT

Solar curtailment involves limiting the solar energy you export during periods when FiTs turn negative. Achieving this requires integration with every solar inverter being used by our customers. 

We’re pressing ahead by prioritising integration with the inverter brands most commonly-owned by our customers which have the potential to allow for solar curtailment during periods of negative FiT. 

i. Solar curtailment control for SolarEdge, AlphaESS and Sungrow customers

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Head to the Settings in your Amber app to enable solar curtailment if you are a SolarEdge customer with a consumption meter, an AlphaESS customer or a Sungrow customer. 

 

  • Solar Edge, SolarEdge with LG Chem, DC-coupled Alpha ESS and Sungrow battery customers with a single hybrid inverter

If you have a SolarEdge inverter and a consumption meter, a DC-coupled Alpha ESS battery, or a Sungrow battery with a hybrid inverter you will now have solar curtailment auto-enabled within the Amber app once you join Amber for Batteries.

SmartShift will look at how much you’re exporting during periods of negative FiT and reduce your solar generation by that amount, matching generation to your household consumption. So if you’re generating 10kw of solar energy, and your house is consuming 8kw and exporting two, your generation will be reduced to 8kw when you enable solar curtailment.

Solar curtailment will only see your solar curtailed during periods of negative FiT. During times when the FiT is above zero, your excess solar will be exported to the grid as usual even with solar curtailment toggled “on”. 

See the above for a screenshot of the Settings section of the app where you can enable solar curtailment.

  • Sungrow battery customers with two hybrid inverters

The “load following” curtailment described above will only work if you have a single hybrid inverter. If you have two inverters, curtailment will look more like what is described below for Tesla customers with SolarEdge inverters, or Hybrid Alpha ESS customers.

That is, during periods of negative FiT, customers with curtailment enabled will see their solar generation switched off entirely (no solar generation) rather than matched to their household energy demand.

When this curtailment occurs, there is a minor lag in restarting the inverters once the FiT is no longer in negative territory (around 2 minutes). 

  • Tesla with SolarEdge inverter, Hybrid Alpha ESS customers

Solar curtailment for hybrid Alpha ESS batteries works a little differently to how it does with those listed above. In this case, SmartShift will curtail your solar (eliminating exports during periods of negative FiT) only when your battery is fully charged. 

If your solar system is capable of generating more energy than your battery can store, and you are not able to consume all of that power within your home at the time, that excess will be exported to the grid for a negative FiT. 

For most customers this is unlikely to be a problem that will occur. For example, if you have a 5kW battery and a 5kW solar inverter, this problem is unlikely. 

However, if you have a Tesla Powerwall and a 3 phase solar system you may be generating up to 3 times more power than your battery can store at any given time and this additional energy will get sent to the grid. We are working on a solve for this issue at present, with more updates coming. 

However, once your battery is fully charged, curtailment will work as described in the section above (for Solar Edge, SolarEdge with LG Chem, DC-coupled Alpha ESS and Sungrow battery customers)

Note: If you have a Tesla Powerwall + SolarEdge inverter with SolarEdge consumption meter, enter the battery details during registration with Amber and then email smartshift@amber.com.au with the serial number of the SolarEdge inverter and request, ‘please enrol my inverter for export control.’

ii. Offgrid mode for Tesla customers

Going offgrid is an option to minimise exports during negative FiT if you have a Tesla Powerwall. Going offgrid effectively isolates the battery from the grid, making it impossible for it to export during periods of negative FiT. Offgrid mode can be enabled via the Tesla app. 

There are only certain conditions in which it’s possible and advisable to use Offgrid mode to counter solar exports during negative FiT. 

  • Your battery will only go offgrid if it is not full, as otherwise there will be nowhere for your solar energy to go. 
  • By contrast, it’s not advisable to enable offgrid mode if the battery is very low. If clouds come over, delaying your battery from charging from your solar, it’s possible you could run out of power. 
  • A single Tesla Powerwall has a max 5kw charge rate. This means if your solar inverter is more than 5kw it may not be advisable to go offgrid. If you try to charge your Powerwall at more than 5kw it will perform a reset/trip and then reset, and you will without power for a short period. For example, going offgrid may work with a 6kw inverter if you're using 1kw or more of energy at the time. 
  • Offgrid Mode only curtails solar production for a single phase solar inverter. If you have a three phase solar inverter going into off-grid mode will island the household to run off batteries, but the three phase solar inverters will continue to operate and export all solar production to the grid.

If you do want to try out Offgrid mode as a means of curtailing exports during periods of negative FiT, we recommend looking for the earliest point in time when FiTs turn negative, then enable offgrid mode. This is one way to ensure you charge up your battery and reduce your solar exports.

Offgrid mode will be automatically disabled by your Powerwall at any time that your household load exceeds what’s available from your solar and battery. 

iii. Village Energy smart plug for Fronius, SMA and Huawei customers

For those with Fronius, SMA and Huawei inverters we are offering a solar curtailment trial of a new piece of hardware being offered by our partner, Village Energy. Village Energy shares the same vision as Amber and our customers, to help communities thrive by using technology to accelerate the energy transition. They use smart automation paired with their EasyLink smart plug to limit solar exporting in line with your unique Amber pricing API.

If you’re an Amber customer with an eligible inverter, head here to register your interest to take part in the Village Energy trial.

 

EV owners

Note: Times when FITs turn negative are the best times to charge your car. We recommend temporarily disabling solar curtailment during this time and re-enabling it once you've finished. 

This is because solar-aware chargers such as Charge HQ, MyEnergy Zappi, Fronius Wattpilot and SolarEdge EV charger look for export and then match charging to that export power. If SmartShift is curtailing your solar during periods of negative FiT these charging solutions see no exports and will not charge. 

If your battery doesn’t charge 

If you turn on solar curtailment in the app and you notice that your battery isn’t charging when you have curtailment switched on, please contact Amber for Batteries support team on smartshift@amber.com.au.

In the meantime, keep an eye out for more updates on how we're helping customers reduce solar exports during periods of negative FiT.

 

4. How we’re incentivising loadshifting to maximise solar usage

Maximising consumption of your home-generated solar is an effective way to further minimise exports during periods of negative FiT, as it reduces what’s leftover to be exported to the grid.

We recommend this as a first priority before enabling curtailment since enabling curtailment basically equates to setting your FiT to zero. Your energy is usually worth more to your home than zero, because it costs more than zero to import it from the grid. 

Here’s a few ideas on how you can go about using more of your solar and reducing exports during negative price periods:

  • Consider adding more electricity use during the day by further electrifying your home. Think: electric hot water heaters, induction cookers, air fryers… or an EV!
  • Shift usage of existing energy-hungry electrical appliances like dishwashers, pool/water pumps, heating and cooling systems to the middle of the day. 
  • Take advantage of innovative tariffs, like Ausgrid’s 2-way tariff.

We highly recommend checking out this blog on Maximising Solar Usage by our Amber for Batteries partnerships manager (and SolarEdge/LG and EV owner), Tim Barson, for more tips on how you can go about this.



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Comments

5 comments
  • Great article, as I think there is a lot of concern, but when the actual numbers are looked at -ve feed in is very small.

    One correction with the Tesla Powerwall, that only curtails solar production for a single phase solar inverter (which is probably the majority).

    If you have a three phase solar inverter going into off-grid mode will island the household to run off batteries, but the three phase solar inverters will continue to operate and export all solar production to the grid (i.e. the opposite of what is desired for curtailment).

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  • Thanks Mark! Appreciate this advice - you are correct and we've updated the article to include this consideration.

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  • You advise not to use solar curtailment when using an EV smart charger as it looks for export before using solar. I'm guessing that the same applies for our Catchpower Green hot water relay, which does the same thing. If so, perhaps that could be added to the article.

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  • Any device that monitors exports will conflict with solar curtailment as it currently stands. We are working on dealing with that at the moment.

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  • I'm an Amber customer with a new Sungrow inverter and sungrow Battery. I purchased them at the recommendation of Amber's recommended supplier upowr.
    I find that the automated curtailment frequently does not cease when the feed in tarrif goes positive. Not only that at the end of the day (6-10pm) when the feed-in tarrif is at a maximum and my battery is full I cannot discharge the battery back to the grid.
    Sometimes the curtailment stops, but it often doesn't.
    I have a 14.6kWof PV, a 10kW inverter and a 19.2kWH battery which I spent 000s on last year and I'm still getting charged for purchasing electricity even though I generate and store more than enough power for my own daily use.
    Whats going on?

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