For Those About to Charge... We Salute You
If you have ever wondered what AC and DC actually mean when charging your EV, you are not alone. Most people nod along when the salesperson explains it, then Google it later in the car park. We are here to fix that.
Quick Answer
At Battery IQ, we explain AC vs DC simply: AC is what comes from your wall, DC is what batteries store. Every time you convert between them, you lose about 5% in energy (like currency exchange fees). If you have solar panels and want maximum efficiency, DC charging skips the conversion and delivers 96-97% of your solar to the car. Home DC chargers are now available in Australia as part of integrated battery systems.
What You Will Learn
- The actual difference between AC and DC (in plain English)
- Why conversion matters and how much energy you lose
- How DC technology is already everywhere in your home
- Why home DC chargers are emerging for solar owners
- How V2H works today with Sigenergy off-grid mode
- Which charger type makes sense for your situation
What Is AC? What Is DC?
Let us start with a 60-second explanation that will actually stick.
AC (Alternating Current)
The electricity that comes from your power points. It is called "alternating" because the current switches direction 50 times per second (50Hz in Australia). Think of it like a wave constantly going back and forth.
Where you find it: Wall sockets, your fridge, washing machine, air conditioner, anything plugged into the wall.
DC (Direct Current)
The electricity that flows in one direction only, like water through a pipe. This is what batteries store and what most electronics actually need to run.
Where you find it: Batteries, solar panels, your phone, laptop, LED lights, USB ports, and yes, your EV battery.
The Key Insight
Your EV battery stores DC power. Your solar panels produce DC power. But your home runs on AC. So every time power moves between these systems, something has to convert it. And conversion is not free.
The Currency Exchange Problem
Here is the easiest way to understand why AC vs DC matters for efficiency:
Imagine you have $100 AUD and you want to buy something in America. You convert your dollars to USD, make your purchase, and bring the change home. Then you convert the USD back to AUD. How much do you have left?
Not $100. The exchange desk took a cut both ways. Maybe you are left with $86-90.
This is exactly what happens with AC charging from solar:
AC Charging Path (Solar to EV)
Result: About 88% of your solar energy reaches your EV (12% lost in conversion fees)
DC Charging Path (Solar to EV)
Result: 96-97% of your solar energy reaches your EV
How Much Energy Are We Actually Talking?
Let us put real numbers on this. For a typical Australian home with solar, how much energy do you lose each year by going through the AC path instead of DC?
The Maths: AC vs DC Charging Efficiency
Starting point: 6.6kW solar system
Annual generation: ~10,000 kWh/year
(Based on 4.2 kWh per kW capacity per day, Australian average)
AC Charging Path:
10,000 kWh → Inverter (-6%) → 9,400 kWh → Car charger (-6%) → 8,836 kWh
Total lost: 1,164 kWh (11.6%)
DC Charging Path:
10,000 kWh → DC charger (-3%) → 9,700 kWh
Total lost: 300 kWh (3%)
The Difference:
DC delivers 864 kWh more per year
864 kWh is a lot of energy. But what does it actually mean in practical terms?
Sydney to Perth. Every Year. For Free.
At typical EV efficiency (5.5 km/kWh), 864 kWh equals about 4,750 km of driving.
Sydney to Perth is roughly 4,000 km. So by switching from AC to DC charging, you could drive across the country on energy you would otherwise lose to conversion.
At current electricity prices (~30c/kWh), that is $260 per year in your pocket instead of lost to heat.
Assumptions (so you can adjust for your situation)
- • Solar system: 6.6kW (most common residential size in Australia)
- • Daily generation: 4.2 kWh per kW of capacity (Australian average; varies by location)
- • Inverter efficiency: 94% (6% loss; good quality inverters)
- • Onboard AC charger efficiency: 94% (6% loss; varies by vehicle)
- • DC charger efficiency: 97% (3% loss)
- • EV efficiency: 5.5 km/kWh (mid-range; Tesla Model 3 is ~6.5, BYD Atto 3 is ~5.0)
- • 100% of solar to EV: Real-world will be lower; scale proportionally
If only 50% of your solar goes to EV charging, halve the numbers. The efficiency percentage stays the same.
DC Is Everywhere (You Just Do Not Notice)
Here is something that might surprise you: DC technology is quietly taking over your home. You just do not see it because every device hides a little converter inside.
Ever bought a ceiling fan recently? The good ones are all DC motors now. They are quieter, use 70% less power, and last longer. But they still plug into your AC wall socket. There is a converter hidden in the base.
| Device | Plugs Into | Actually Runs On | Hidden Converter? |
|---|---|---|---|
| Phone charger | AC (wall) | DC (5V) | Yes (the brick) |
| Laptop | AC (wall) | DC (19-20V) | Yes (power brick) |
| LED lights | AC (wall) | DC (12-24V) | Yes (driver inside) |
| DC ceiling fan | Hardwired to AC | DC | Yes (in the motor) |
| Solar panels | N/A | DC (native) | No |
| EV battery | AC or DC charger | DC (native) | Depends on charger |
The pattern is clear: most modern technology wants DC power. We just force it through AC conversion because that is what comes out of our walls. It is like everyone speaking English at an international conference, even though most attendees would prefer their native language.
Why Is Everything AC Then?
It comes down to one invention: the transformer. Back in the 1890s, Edison championed DC while Tesla and Westinghouse backed AC in what became known as the "War of Currents".
The challenge was transmitting power over long distances. Electricity loses energy to heat in the wires, and the higher the current, the more you lose. The solution is high voltage, low current for transmission, then step it back down for homes.
AC could do this cheaply with transformers (just coils of wire, no moving parts). DC had no practical way to change voltage back then. So AC won, and the entire grid was built around it.
The irony: Modern electronics can now convert DC voltage efficiently. We actually use HVDC (High Voltage DC) for some long-distance transmission today because it is more efficient for undersea cables. If we designed the grid from scratch now, we might choose DC. But we have 130 years of AC infrastructure already built, so we are stuck converting DC solar → AC grid → DC battery → DC devices. It is legacy infrastructure, like QWERTY keyboards.
Why Your EV Speaks Both Languages
Every modern EV has two charging ports (sometimes combined into one socket):
AC Charging Port
Uses your car's onboard charger to convert AC to DC. Limited by the size of that onboard charger, typically 7-11kW for most EVs, 22kW for some European models.
Speed: 7-22kW (home charging)
DC Charging Port (CCS2)
Bypasses your car's onboard charger completely. The charger does all the work. This is why public DC fast chargers can pump in so much power.
Speed: 50-350kW (public) / 12.5-25kW (home)
Think of it like your car being bilingual. It can accept power in either language, but DC is its native tongue. When you use DC, you are speaking directly to the battery.
| EV Model | AC Max | DC Max | Notes |
|---|---|---|---|
| Tesla Model 3/Y | 11kW | 250kW | 22kW AC not available |
| Polestar 2/3 | 11kW | 250kW | 22kW AC wasted |
| BYD Atto 3 | 7kW | 80kW | Lower AC limit |
| BYD Dolphin | 7kW | 80kW | Popular entry EV |
| BYD Seal | 7kW | 150kW | Sports sedan |
| Hyundai Ioniq 5/6 | 11kW | 350kW | Fastest DC charging |
| Zeekr 7X | 22kW | 200kW | Can use full 22kW AC |
Planning Solar, Battery, and an EV?
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Analyse My BillHome DC Chargers Are Here
Until recently, DC charging meant finding a public fast charger. Now you can have DC charging at home, and it makes a lot of sense if you have solar panels.
Sigenergy is leading this space in Australia. Their system combines a home battery (SigenStor) with an optional DC EV charger that connects directly to the same DC bus as your solar panels. No currency exchange required.
| Charger Type | Speed | Efficiency from Solar | Notes |
|---|---|---|---|
| AC Charger (any brand) | 7-22 kW | ~88% | Standalone, works with any EV |
| DC Charger (integrated) | 12.5-25 kW | 96-97% | Requires compatible battery system |
Important: Two Types of Home DC Chargers
Integrated DC chargers (like Sigenergy) connect to a compatible battery system's DC bus. They are not standalone products - you need the battery system too. The DC charger module itself is around $3,000-5,000, making this the more affordable path if you are already investing in a home battery.
Standalone bidirectional chargers (like V2Grid Numbat) connect directly to your home's electrical system. No separate battery required - your EV is the battery. The Numbat supports both CCS2 and CHAdeMO, and uniquely offers both V2H and V2G (grid export) today. At around $10,000 installed, it is a genuine option for those who want full bidirectional capability without a battery system.
Who Makes Home DC Chargers?
The home DC charger market is still emerging. Here are the main players in Australia:
- Sigenergy - Market leader for integrated solar, battery, and EV charging. Their SigenStor system includes optional 12.5kW or 25kW DC EV charger modules. If you are planning a home battery anyway, this is the most seamless option.
- RedEarth/Ambibox - Australian company partnering with German manufacturer Ambibox. Their 11kW three-phase DC charger launched in early 2026. Tested with BYD, Polestar, Hyundai, and MG vehicles.
- V2Grid Numbat - First CEC-certified bidirectional charger in Australia. Supports both V2H and V2G (grid export) today - the only charger in Australia with full V2G capability enabled. Works with both CCS2 and CHAdeMO connectors, making it compatible with most EVs. Australian-designed, 7kW output.
- Wallbox Quasar 2 - Popular in the US and Europe, but limited availability in Australia.
What About Tesla?
Tesla's Wall Connector is an AC charger (up to 11kW for most Tesla vehicles). It is a great charger, but it goes through the same currency exchange as any AC charger.
Powerwall 3 can be DC-coupled. It has an integrated solar inverter (up to 11.5kW) that connects directly to your solar panels, keeping solar as DC until it reaches the battery. However, it can also be AC-coupled with an existing solar system. The key difference from Sigenergy is that Powerwall does not offer an integrated DC EV charger, so while your battery storage is efficient, your EV charging still goes through AC conversion.
If you want a DC-coupled system that keeps solar as DC all the way to your EV, Sigenergy is currently the leading option in Australia, with an integrated DC EV charger module that connects directly to the battery's DC bus.
V2H Is Here (Your EV Can Power Your Home Today)
Here is where DC charging gets really interesting: V2H (vehicle-to-home).
Your EV battery is massive. A Polestar 3 has 111kWh of storage. A Tesla Powerwall has 13.5kWh. Your car could power your home for 3-4 days. V2H lets you actually use it that way.
What V2H Enables
- Blackout protection: Your EV becomes a backup generator. No petrol needed.
- Peak shaving: Draw from your EV during expensive peak hours (3-9pm), charge overnight when power is cheap.
- Solar storage: Your EV becomes extra battery capacity for days when you generate more than you use.
- Grid support: Eventually, V2G (vehicle-to-grid) will let you earn money by supporting the grid.
V2H Works Now (But V2G Does Not)
V2H is available today with Sigenergy via "off-grid mode". This isolates your home from the grid and powers it from your EV battery. You can use this for backup power during blackouts, or to power your home from your EV at night. The mySigen app includes a "Go Off Grid" feature, and the system automatically switches to off-grid mode during grid outages.
V2G (vehicle-to-grid) is not yet enabled on Sigenergy. This is the feature that lets you export power back to the grid and get paid for it. Sigenergy says this will be enabled via an over-the-air update once Australian standards are finalised. Note: The V2Grid Numbat already has V2G enabled if you want grid export capability today.
Compatible EVs for V2H: Sigenergy has tested with Volvo, BYD, Hyundai, Kia, VW, Porsche, and NIO. Tesla compatibility has shown mixed results in testing. The V2Grid Numbat now supports both CCS2 and CHAdeMO, so works with most EVs.
How Off-Grid Mode Actually Works
Sigenergy V2H uses "off-grid mode" which works like this:
- • Grid isolation: The system disconnects your home from the grid (critical for safety - prevents backfeeding to downed power lines)
- • EV as power source: Your EV battery discharges through the DC charger to power your home
- • Automatic switching: System detects grid outages and switches automatically (true UPS with ~20ms switchover)
- • Manual control: The mySigen app has a "Go Off Grid" feature for intentional use
This works without V2G approval because you are not exporting to the grid - you are simply powering your own isolated home. Think of it as using your EV as a giant portable generator, but without the noise or petrol.
Off-Grid Mode Limitations
Off-grid mode is designed primarily for backup power, not daily toggling. You cannot currently use it to avoid negative pricing periods or switch on/off throughout the day like a regular operating mode. For daily solar optimisation, the system uses its standard modes (Max Self-Consumption, Time-based, etc.) while your car charges normally.
When AC Is Actually Better
We have been singing DC's praises (pun intended), but AC charging still makes sense in several situations.
AC Wins When...
- ✓ You charge overnight from the grid on cheap rates
- ✓ You do not have solar panels
- ✓ You do not want a home battery system
- ✓ Budget is the priority (AC chargers start from $800)
- ✓ You rent and cannot install a battery
DC Wins When...
- ✓ You have solar and want maximum efficiency
- ✓ You are already investing in a home battery
- ✓ V2H/V2G capability matters to you
- ✓ You want one integrated system
- ✓ Long-term savings outweigh upfront cost
The Honest Truth About Grid Charging
If you charge from the grid at night (no solar involved), AC and DC are about the same efficiency. The currency exchange problem only matters when you are converting solar DC to AC and back. On a rainy day with no solar production, your AC charger works just as well.
Which Charger Is Right for You?
Let us make this simple. Answer these questions:
Question 1: Do you have (or plan to get) solar panels?
No: Get an AC charger. The efficiency advantage of DC only matters when you have solar to capture.
Yes: Continue to question 2.
Question 2: Are you planning to buy a home battery?
No: Get an AC charger with solar diversion (like Zappi or Sigenergy AC). You will still lose some efficiency, but you will prioritise solar when available.
Yes: Continue to question 3.
Question 3: Is maximising solar efficiency or V2H important to you?
No: Get an AC charger. It will work with your battery system and cost less.
Yes: Consider a home battery with good DC charging integration. Sigenergy is the leading example, with an integrated DC EV charger module that connects directly to the battery's DC bus.
Our Recommendation
For most Australians today: A quality 11kW AC charger is the sweet spot. It works with any EV, charges overnight on cheap rates, and can prioritise solar when paired with smart features.
For maximum efficiency: If you are planning a home battery, consider one with integrated DC EV charging like Sigenergy. The DC module adds cost upfront but pays back through efficiency gains over time, plus you get V2H capability via off-grid mode today (and V2G when it is enabled).
Content reviewed by Battery IQ Energy Analysts | Supply-only pricing based on Australian wholesale + retail markup, January 2026 | Sources: Sigenergy Australia, Clean Energy Reviews, Solar Choice, AEVA, V2Grid Australia | Installation costs vary by site | V2H/V2G status verified January 2026
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