How Do 3 Phase Meters Work with Single Phase Solar?
Installing a solar system with a single-phase inverter on a home that uses a 3-phase supply raises important questions about how energy is measured and billed. The way 3-phase meters interact with single-phase solar depends on both electrical flow and how your energy retailer calculates usage.
What Happens When You Install Single-Phase Solar on a 3-Phase Supply?
When solar panels are connected to just one phase of a 3-phase system, two types of realities occur at the same time—how electricity moves through your system and how your meter records it.
1. The Electrical Reality
If your home has a 3-phase power supply with a balanced load of 2 kW on each phase, and your solar system is connected to just one phase using a single-phase inverter producing 6 kW, here’s what happens. The solar will first supply the 2 kW demand on that same phase. The remaining 4 kW will be exported to the grid. Meanwhile, the other two phases still draw 2 kW each from the grid. The retail meter sees one phase exporting 4 kW, and two phases importing 2 kW each.
2. The Billing Reality
Even though energy flows differently across the phases, your smart meter treats them as one combined system. It nets out the total energy imported and exported across all three phases. So in this case, it adds up 4 kW of exports and 4 kW of imports and registers a net flow of zero. That means you are neither charged nor credited during that time. The billing is based on the overall balance, not individual phase flows.
3. Optimising Usage Across All Phases
To make the most of your solar generation, it helps to spread the system across all three phases. This can be done with a 3-phase inverter or with separate single-phase inverters on each line. When solar is matched to the loads on each phase, the system works more efficiently. You reduce grid interaction, avoid voltage imbalance, and minimise inverter throttling. This setup ensures more of your solar energy is used directly in your home.
What is Net Metering and How Does It Work?
Net metering is the process that allows you to receive credit for the excess electricity you send back to the grid. It plays a key role in making single-phase solar viable on 3-phase homes.
Even though your inverter sends energy to only one phase, the meter evaluates your total electricity use across all three. For instance, if you export 4 kWh on one phase and import 1 kWh each on the other two, the system nets this out. You’re not charged for 2 kWh of imports. Instead, you receive credit for 2 kWh of net exports.
This feature is what makes net metering beneficial. It ensures that all the solar energy you generate is counted toward your electricity bill, no matter which phase it is sent through.
Is It Worth Using a Single-Phase Inverter on a 3-Phase Home?
Yes, a single-phase inverter is often a cost-effective solution for homes with solar systems up to 10 kW. You save money on equipment and installation, yet still benefit from the total solar generation thanks to net metering. Your electricity bill reflects the net result across all phases, ensuring you get full value for your solar production.
For homes with higher energy demands, such as those with electric vehicle charging, pool pumps or large air conditioning units, a 3-phase inverter might be a better option. It distributes solar generation more evenly across the phases, helping to maintain balance and reduce the risk of voltage issues.
Should You Consider Spreading Solar Across All Three Phases?
If you can, spreading generation across all three phases ensures your solar production closely matches your household demand. Whether you use a 3-phase inverter or separate inverters on each phase, this approach minimises the need for grid imports and maximises self-consumption. It can also reduce technical issues like voltage spikes and inverter limitations.
How to Check if Your Home Has a 3-Phase Connection?
To find out whether your property has a 3-phase supply, check your switchboard. Look for the main switch and count the number of poles. A single-phase main switch takes up one pole width, while a 3-phase switch is three poles wide. This quick check helps you plan your solar setup accurately.
Get in Touch
Looking to compare prices or explore which inverter setup suits your home best? Contact us for a quote and more details about the benefits and considerations of using single-phase or three-phase inverters on a three-phase property. Fritts Solar has the experience to design a system tailored to your current energy use and future requirements.