Network-imposed solar system size limits can sometimes squash our dreams of tiny bills, but Glen from Perth has discovered a game-changing solution.
Bucking traditional constraints, he’s unlocked a brilliant strategy many haven’t considered.
Step into a future where living large doesn’t mean large bills: as we dive deep into the untapped potential of semi-off-grid appliances.
Glen’s Solution: Going Semi-Off-Grid with Hybrid Solar Appliances
Glen, a retired engineer from Perth, installed rooftop solar in 2010. Western Power permitted only a 5kW inverter at that time, distributed over three phases. To harmonise with the grid, Glen split the 5kW between a 2.0 kW inverter and a 2.8 kW inverter on separate phases.
But rules change. Now, Western Power allows just 3kVA per phase for single-phase solar inverters on a 3-phase setup. Without any updates, Glen is nearing his inverter capacity on two of those phases.
Western Power maximum basic EG (embedded generator) system capacity and export limits. Image: Western Power
Batteries First, But Glen Soon Realised: More Solar was the Answer
In 2021, Glen added a Powerwall 2 battery. Just five months later, he installed another. This meant a 2.8 kW inverter with a 13.5 kWh Powerwall on one phase and a 2 kW inverter with a 13.5 kWh Powerwall on another. Seems excessive? While Glen stands by his choice, one could argue he missed the mark.
With limited solar on each phase, an extra battery didn’t up his solar intake. The numbers for a second battery just didn’t add up. Glen’s flat rate tariff, smaller rooftop system, and daytime power usage as a retiree pointed to one solution: more solar panels.
Aware of this and nearing his limit on two phases due to Western Power’s rules, Glen faced a choice. He could add a 3kW system to the third phase or overhaul his existing setup for a new 3-phase inverter and solar arrays, fitting within the 5kW per phase rule.
Glen chose a unique path.
Solar Powered Hybrid AC/DC Air Conditioners
In his search for answers, Glen uncovered air conditioning units that run on either grid AC, or DC from a dedicated solar array. These hybrid air conditioners1, without any ability to sync or return power to the grid, neatly and legally evade DNSP grid connection rules.
Glen highlighted the appliance’s versatility with its three distinct operating modes:
- Completely off-grid, running solely based on what the solar panels produce.
- Grid-connected with an AC limiter on, drawing a capped 400W from the grid.
- Grid-connected without an AC limiter, allowing the appliance to pull extra power from the grid, ensuring it runs at peak capacity.
“Wanting to remove my old gas fire and to trial a Solar AC/DC split air conditioner in October 2021 I installed a 5kW unit in my lounge room with 7 x 370W solar panels. The unit has performed as expected so I decided to replace the conventional AC installed in the upstairs room with another 5kW Solar AC/DC unit.”
“Last summer, the two Solar AC/DC air conditioners, by leaving them off the grid, simply starting in the morning as the sun rose and shutting down as the sun set, kept my house temperature controlled. With the assistance of a wood fire, the same is generally applying this winter.”
Solar ACDC Split Hybrid Air Conditioner – no batteries needed! Image: Solar ACDC
But Glen didn’t stop there!
Solar Powered Hybrid AC/DC Heat Pump HWS And Swimming Pool Heat Pump
In his research, Glen discovered the emerging Solar AC/DC Heat Pump for hot water and the Solar AC/DC Pool Heat Pump Heater/Cooler. Both could be powered by the grid or independent solar panels—no batteries required. Taking a chance, Glen equipped his home with these innovative systems and the necessary solar panels.
“Since commissioning the HWS has not drawn any power from the grid and is now off the grid. I am extremely confident that by giving it priority use of the 14 panels it will remain off the grid even under extreme periods of low solar production.”
“The pool heat pump is also performing to expectations. In the week it has been connected (running from about 10 am to 4 pm) it has raised the 60,000 litre pool temperature by about 5 degrees. It will soon have it warm enough for exercise swimming. I am also looking forward to it keeping the pool cool enough as summer progresses.”
In just about eight months post-installation, Glen reports a mere 29 kWh drawn from the grid, while sending back 3,570 kWh.
Harnessing More Solar Within the Rules
Tapping into the potential of hybrid AC/DC systems is a clever way to maximise solar usage without breaching network constraints. The absence of a grid-tied inverter means these panels fly under the radar during capacity assessments. Ensure your switchboard and grid connection can manage the load in grid mode, and you’ve got a winning setup.
A side note: Glen’s battery usage might not be optimal, but that’s a topic for another day.
DNSP rules, though seemingly restrictive, aim to balance a transitioning grid—one adapting to varied, sporadic energy sources.
We often challenge set boundaries. With a touch of ingenuity, you can not only make the most of your solar quota but also contribute to a steadier grid during peak demands.
Footnotes
- don’t confuse these appliances with ‘hybrid solar airconditioners’ from other companies that claim they use solar thermal to improve efficiency – Finn tells me he looked into these at CSIRO and could find no efficiency improvements ↩
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