Catch Solar Relay: Load Diversion For Local Grid Stability

Catch Solar Relay

A properly configured Catch Solar Relay can help increase your solar energy self-consumption and individually make a small contribution towards grid stability.

Australian solar owners: you now have a new option to put your self-consumption on autopilot while helping both stabilise the grid and enabling more of your neighbours to install solar power systems.

Catch Power is finally shipping its much anticipated multi-load Catch Solar Relay, so SolarQuotes caught up with the Glen Innes company’s co-founders Scott Young and Jason De Jong to chat about the device.

Catch Power is already a local success story, with 4,000 units of its Green CATCH product, which diverts excess solar energy production to water heating. Catch Power contacted us after reading about the Paldin system that uses air conditioning as the target diversion load.

The company’s first two products, Blue CATCH and Green CATCH, had the consumer in mind, but designer De Jong said the company wanted to add other loads to the roster – because that would expand households’ contribution to stabilising the grid.

The Catch Solar Relay is a unit that doesn’t focus just on water heaters, but adds appliances such as air conditioners, pool pumps, water pumps, lighting circuits, fans and underfloor heating to the list.

Catch Power’s Focus

De Jong and Young told SolarQuotes the big picture has to be the motivation for everything they do. De Jong said if the fundamental issue – decarbonising the economy – isn’t the fundamental reason they design something, the solutions aren’t right.

“What underpins every waking moment of the day isn’t the electronics, it’s the fundamental requirement to decarbonise the economy”, De Jong said.


“Our focus is making sure we can transition as fast and hard as we can.”

While there are disputes about the degree to which solar-driven voltage rise is constraining the network today (we discussed UNSW’s research into the causes of voltage rise here), there’s no doubt that it’s going to be a growing roadblock to new household solar power uptake – hence the renewed attention on using local consumption to make use of the excess power. That’s better than having consumers trying to send unwanted energy to the network and having their inverters shut down to protect the network.

Catch believes more than 80% of what’s now exported could be redirected to self-consumption, which would go a long way to relieve the pressure on the network and enabling further renewable deployment.

Catch Solar Relay

A simple approach to load diversion: the Catch Solar Relay

De Jong told us Catch Power wanted a system that could be as autonomous as possible – it should respond to a local signal rather than waiting for an instruction from some kind of centralised system.

Voltage – the notional 230V the network delivers to the household – is the obvious local signal.

“We need devices that understand more about what’s required to maintain a stable network, rather than devices that just respond to central control.”

Macro Versus Micro

De Jong said at the macro level, the important signal of network health is frequency – which is why FCAS (Frequency Control Ancillary Services) is the service that delivers such handy revenue to the Tesla-powered Hornsdale Power Reserve.

Frequency matters at the household level, but De Jong said if a household is observing significant frequency drift, there’s something seriously wrong at the macro level.

Voltage trends, on the other hand, tell you what’s going on more locally.

“Measuring and interpreting voltage seems like a simple concept, but what you’re looking for is … how is the voltage changing over time?”

If you carry out detailed monitoring at the household level, he said, the instantaneous voltage is all over the shop – but with that detailed monitoring, you can also see voltage changing over time, which is what matters in making power diversion decisions.

De Jong stated with the smarts to behave autonomously:

“unknown to each device, their actions are collectively working to support the network.”

There’s a small bit of secret sauce involved, because if all the devices responded identically and simultaneously to network conditions, there would be a huge overshoot. You don’t want 100 air conditioners (for example) starting in the same second because voltage started rising.

“So they [the Catch Relay devices – SQ] don’t all act at the same time – a single device might ramp up a load but not all devices at once.”

As well as a voltage sensor and the ability to power up different loads in the consumer’s home, the relay has a current transformer to measure import/export, also to inform decision-making.

Loading Up The Local Network

An important aspect of the Catch Solar relay, one that won’t matter to the individual but could make it attractive to network operators, is that a network of household relays “below the transformer” is effective even if not all the households have solar panels.

Taking just the water heater as the connected load, in a white paper provided to SolarQuotes the company describes the operation like this:

“CATCH Solar Relays do not rely on any form of communication to coordinate ramp up and ramp down. CATCH Solar Relay uses a combination of inherent differences in the electrical wiring between each installation, and statistically distributed ‘switch on’ and ‘switch off’ times. The combination of these two things means once an intervention event is detected the loads are gently ramped up or down.”

If Catch Power can get the relay widely deployed, Young says it could “free up” as much as 38% of the solar generation in the network.

“If you can take back 38% of all solar in the network, it means a whole lot more solar can go in,” Young said.


“That’s important for a lot of reasons – we have international obligations to meet, there’s an electorate that’s hungry for solar, and the environment needs it. Coming up with technologies that will allow more solar to go into the network is a great idea”.

And De Jong pointed out having a significant percentage of available solar power operating self-consumed loads acts as a strategic reserve for the network.

“Say there’s a failure in the system, this energy reserve is built into the NEM – so there’s frequency variation, the hot water services turn off, and flood the network with needed energy.”

About Richard Chirgwin

Joining the SolarQuotes blog team in 2019, Richard is a journalist with more than 30 years of experience covering a wide range of technology topics, including electronics, telecommunications, computing, science and solar. When not writing for us, he runs a solar-powered off-grid eco-resort in NSW’s blue mountains. Read Richard's full bio.


  1. Bret Busby in Western Australia says

    And the retail price (including installation) is?

    • Finn Peacock says

      $357.50 including GST. plus installation. Installation depends on what you are controlling.

      • It’s cool tech but I’m still struggling to see the case for installing one.

        The bill savings just aren’t there to make up the $500+ cost of having one installed, while network benefits go to the network, not the householder.

        If the network wants to install one, sure I’ll consider letting them. But my heating and cooling is going on when I need it to, not when it’s convenient for them.

        Savings for hot water are simply not there where HW off-peak rates are low (e.g. NSW). Pool pump already operates on a timer. Yes it’s a dumb timer but it also only costs $20 to get 90% of the effectiveness of smart PV diverter.

        And the network can always turn on my off-peak hot water circuit if it wants to add some daytime load…

        • Greg O'Grady says

          That sounds like the sort of self centred attitude that we need… 🙁

          • It’s not self centred, it’s pragmatic.

            I’m all for good solutions to help address peaks and troughs in grid power supply and demand. Consumers can play a part but solutions have to make sense.

            In this case it makes no sense.

            Why should people fork out $500+ to install something for which all the benefit goes to a monopoly corporation with zero accountability to consumers?

            Please enlighten us on the case for why the consumer should be the one to bend over and take it up the clacker?

      • chris king says

        I have a 6.6kw solar array with a 5kw inverter…..just converted my electric hws and oven to natural gas. Basically all i have left to run on elec. is my big lg fridge, front loading washing machine/dryer sometimes, tv, computer and dishwasher, also new Daiken split system aircons, which i only use now and again, as i live alone. I have also replaced ALL my lighting with LED lights. I live in Horsham Victoria. I only moved into this place mid Januay 2021. Do you think my power bill will be somewhat less than the previous owner after what i have done?…still waiting for my first bill, and is there anything else i can do to save on electricity, such as the catch solar relay?????

        • May I ask why you converted to gas despite the big push to electrify? I myself am on gas for HWS and stovetop and am saving up to convert to elec.

  2. Great, congratulations to all at CP, especially Scott Y for pointing out that “we” have international obligations, that devices like this have the potential to allow your local energy service providers to assist home owners and small business to better manage their overall energy usage and hence carbon footprint?
    Dennis Pont
    Solar Energy Options

  3. Peter Newman says

    I am considering installing a Derby-style Heat Bank as a background heat source for our well-insulated home in the Clare Valley. We have a Redback Series 2 hybrid inverter and – currently – 4.8 kWh of batteries (hope to upgrade to the full 9.6 kWh soon).
    I understand that the Redback inverters have up to 4 (four) controlled outputs from the inverter.
    Do these do the same job as these Catch Solar Relays?
    Peter Newman

  4. Sorry but why should I spend that money? Are there any benefits for me? I don’t get it.

  5. But how do we collectively help to supply daylight base power so that snowy 2 can pump that water up hill. Or do we have to build a Nuclear ( or is it ‘New cue la’ like JW Bush called it) power station to supply those pumps?

    • Erik Christiansen says

      Listen closely, and we hear quite a few Americans pronounce nuclear as ‘New killer’; after Chernobyl and Fukushima, the term is profoundly accurate.

      Mind you, “New killer” is also the most expensive form of electricity generation, even when the shutdown and containment costs are socialised. It’s more expensive than coal, which is dead meat as sustainable generation saves cost, not just lives and civilisation.

      The energy transition is happening too slowly, though. The full extra cost of dragging our backsides will yet exceed all the wars we’ve had, even if extinction is avoided. (In the short term, it is more profitable for fossil merchants not to. 😉

      • What I was getting at is that if the daytime power is to be used locally what power supply is the system going to use to pump all that water back up the 24 km 10 metre pipe to where it was some 700 metres up the hill for later?

        • Peter Marsh says

          Dear Trevor, It’s all down to economics. If you look at charts for your costs for electricity you see an expensive block around sunrise, cheap around midday, expensive late afternoon and real cheap at night-time. Well, pumping of water will start at the cheap times and release at the expensive times. Aim: to maximize money generation by the electricity generators. It’s not that complicated.

  6. Stephen Helm says

    I have a tesla 13kwh battery installed with my 10 kw panels and having 2 inverters connected the software that came with the tesla battery makes sure the power producded during the day is used by the house first and any left over kw’s are then sent to the battery than any extra kw’s are then diverted to the grid sometimes all happening at once on a really sunny day as I am lucky all my panels are facing the sun and no shade to interfere with production. The app that came with the battery even lets you set the minimum % battery level for blackout, the battery has a reserve for when the the grid goes down so why would I want to spend the extra money for another device that does the same as I already have?

  7. Larry Gray says

    Renewables isn’t going to cut the mustard. Nuclear or coal/gas fired stations are needed.

    • Erik Christiansen says

      If the road to Hell is paved with good intentions, then the road to extinction is paved with rampant delusions. It is a researched and documented fact that a modest fraction of Australia’s existing exploitable pumped hydro sites is sufficient for _all_ of our energy storage needs, allowing wind and solar to completely replace both climate destroying, and self destroying radioactive, generators. How much CST there will be in the mix is a commercial matter; maybe useful, but not essential for 100% renewables with existing technology.

      Even that gas pipeline in WA has just had its viable life expectancy cut from 2090 to 2063 by the owners. Observers note that it will most likely be put out of action by 2050, requiring even faster write-down. With gas on the way out, it abundantly clear that the very best carbon sequestration method is shutting down all coal mines pronto. Renewables can employ more than the few coal miners we have – out in healthy fresh air and sunshine. It is only the corporate parasites who stand in the way.

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