Solar Excess EV Charging: How to Charge Your Car with Free Energy

If you have solar panels on your roof and an electric vehicle in your driveway, you're sitting on one of the best cost-saving combinations available to Melbourne homeowners. Solar excess EV charging lets you use the surplus power your panels generate during the day to charge your car, instead of exporting it back to the grid for a feed-in tariff that's often just 3-5 cents per kWh.

At Power Amp Electrical, we install smart EV chargers across Western Melbourne and Geelong that are specifically designed to make solar charging effortless. Here's how it works and what you need.

What Is Solar Excess Charging?

Solar excess (or surplus) charging is a feature available on certain smart EV chargers that monitors your home's solar production in real time. When your panels are generating more electricity than your house is using, the charger automatically diverts that surplus energy into your EV.

The key difference from regular scheduled charging:

• Regular charging: Draws a fixed amount of power from the grid at a set time (usually overnight on a cheaper tariff)
• Solar excess charging: Dynamically adjusts charging speed based on how much solar power is available right now, aiming to use only free solar energy

On a sunny Melbourne day, a typical 6.6kW solar system might export 3-5kW during the middle of the day when nobody's home. That's enough to add 20-35km of range per hour to your EV, completely free.

Why It Makes Financial Sense

Let's look at the numbers for a typical Melbourne household:

Even compared to off-peak charging, solar excess saves $560-$770 per year. Over the life of a charger (10+ years), that's a significant return on investment.

And with Victorian feed-in tariffs continuing to drop (many retailers now offer just 3-5c/kWh for exported solar), the opportunity cost of sending that power to the grid is minimal.

How Solar Excess Charging Works

The Basic Setup

1. A CT clamp (current transformer) is installed on your meter board's grid connection. This small sensor measures how much power is flowing to and from the grid in real time.
2. The CT clamp communicates with your smart EV charger (via wireless or wired connection).
3. When the charger detects that you're exporting solar power, it starts charging your EV. When solar production drops (clouds, evening), it pauses or reduces the charging rate.

Charging Modes

Most smart chargers offer multiple modes you can switch between:

• Eco/Solar Only: Only charges when there's excess solar. Zero grid draw. Charging speed varies with the sun, typically between 1.4kW and 7kW.
• Eco+ / Solar Boost: Prioritises solar but supplements from the grid to maintain a minimum charging rate. Good for days when you need a full charge regardless of weather.
• Fast / Grid: Ignores solar and charges at full speed from whatever source is available. Use this when you need to charge quickly before heading out.

The beauty of these modes is flexibility. Set it to Eco when you're home all day and don't need the car. Switch to Fast when you've got a long drive tomorrow.

Best Smart Chargers for Solar Excess Charging

Myenergi Zappi

The Zappi is purpose-built for solar integration and is one of the most popular choices in Australia.

• Three charging modes (Eco, Eco+, Fast)
• Works with any solar inverter (no brand lock-in)
• Built-in energy monitoring and scheduling via the myenergi app
• Available in 7kW (single-phase) and 22kW (three-phase)
• Can integrate with battery storage systems

Fronius Wattpilot

If you already have a Fronius inverter, the Wattpilot offers seamless integration.

• Direct communication with Fronius inverters for precise solar tracking
• Solar surplus mode built in
• Also works with non-Fronius systems via CT clamp
• 7kW and 22kW models available

Tesla Wall Connector with Powerwall

Tesla's Wall Connector doesn't have standalone solar excess detection, but paired with a Powerwall and Tesla's energy ecosystem, it can prioritise solar through the Tesla app's energy settings.

SolarEdge EV Charger

Designed for homes with SolarEdge inverters. Manages solar excess charging through the SolarEdge monitoring platform.

What You Need to Get Started

1. Solar System (Already Installed)

Most Melbourne homes with solar have systems between 5kW and 13kW. Even a smaller 5kW system can provide meaningful solar charging. Larger systems (10kW+) can comfortably charge an EV and run the house simultaneously.

2. Compatible Smart Charger

The charger needs to support solar excess detection, either through a CT clamp or direct inverter integration. Not all EV chargers have this feature; standard "dumb" chargers and many basic smart chargers don't. Our EV charger installation guide covers the full range of options.

3. Electrical Infrastructure

Your switchboard needs a dedicated circuit for the EV charger (minimum 32A for a 7kW charger). If your switchboard is older or already near capacity, a switchboard upgrade may be required before installation. See our switchboard upgrade cost guide for what to budget.

A single-phase home can support a 7kW charger. For faster 22kW charging, you'll need three-phase power.

4. CT Clamp Installation

The CT clamp is installed at your meter board during the EV charger installation. It's a small addition to the job but critical for accurate solar tracking.

Common Questions

Can I charge my EV with solar if I have a battery too?

Yes. Most smart chargers work alongside battery systems. You can configure priority: typically solar charges the battery first (to cover evening usage), then excess beyond the battery goes to the EV.

What happens on cloudy days?

In Eco mode, charging slows down or pauses when clouds reduce solar output. The charger automatically resumes when production picks up. On heavily overcast days, you may get minimal solar charging and can switch to grid power if needed.

How much solar do I need to charge an EV?

A rough guide:

• 5kW system: 15-25km range added per day from solar (good for daily commuters)
• 6.6kW system: 20-35km per day
• 10kW+ system: 35-55km per day

According to the Australian Bureau of Statistics, most Australians drive less than 40km per day, so even a modest solar system can cover daily driving needs.

Do I need to be home for it to work?

No. Once configured, solar excess charging runs automatically. Plug your car in before you leave for work, and it charges itself when the sun comes out. Check progress from your phone via the charger's app.

Will solar charging damage my EV battery?

No. Variable-speed charging is perfectly safe for EV batteries. In fact, slower charging (which solar excess often provides) is generally better for long-term battery health than consistently fast charging.

Installation: What to Expect

A solar excess EV charger installation typically takes half a day and includes:

1. Site assessment and switchboard check
2. Mounting the charger (garage wall, carport, or external wall)
3. Running a dedicated circuit from the switchboard
4. Installing the CT clamp at the meter board
5. Configuring the charger's solar modes and connecting to WiFi
6. Testing and demonstrating all modes

If a switchboard upgrade is needed, we'll usually complete both on the same day.

The Bottom Line

Solar excess EV charging is one of the highest-return energy efficiency upgrades available to Melbourne homeowners with existing solar. The charger pays for itself through avoided electricity costs, and once it does, you're driving on free energy from your roof.

If you already have solar and an EV (or you're about to get one), a smart charger with solar excess capability should be your first call.

Get a free EV charger quote or call us on 1300 797 267 to discuss your solar setup.