If you need three-phase power and only have single-phase, don't buy a transformer converter. Buy a high-power inverter. It's simpler, more efficient, and often cheaper for running the typical loads most installers and project developers deal with.

I've spent the last five years coordinating rush orders for solar and backup power systems at GoodWe. In my role, I handle everything from a leak in a commercial installation in Perth to a last-minute change order for a home battery setup in the UK. When someone calls needing a solution for a 10kW motor or a workshop tool, they're usually frantic about the 'correct' transformer. They assume a single phase to three phase transformer converter is the only path. In March 2024, a client in Canada needed to power a 3-phase CNC router in a warehouse that only had a 240V single-phase drop. Normal quote for a suitable rotary converter was $4,500, plus freight. They had 72 hours. I told them to look at a 7.2kW growatt or a power inverter backfeeding the load. It worked. The client saved $3,000.

The fundamental issue is that most people—including some wholesalers—default to a transformer because it's the 'traditional' solution. But the technology has moved on. What was best practice in 2020 may not apply in 2025. A transformer converter (rotary or static) is basically a big, heavy, 50Hz-60Hz machine that creates a synthetic third phase. It's inefficient, bulky, and has a voltage drop. A modern high-power inverter, specifically a solar hybrid or a dedicated motor drive, is an electronic device that does the same job—converts DC (from solar) or AC (from the grid) into a clean, adjustable three-phase output.

Here's the key difference: a standard 48v lithium battery price for a 5kWh system is now under $1,000. Pair that with a 5kW hybrid inverter, and you have a three-phase UPS that can handle a 50% surge. A comparable transformer that can provide a 50% surge derate is going to cost 3-4x that. I'm not saying transformers are dead. For a massive, constant load like a 100hp industrial pump, a transformer is still the heavy lifter. But for 90% of installations—a farm workshop, a small commercial kitchen, a home with a solar carport—the inverter is the better tool.

What changed was the refinement of the power inverter topology. The old generation of inverters had terrible harmonics—they'd make a motor hum and overheat. The modern ones, like GoodWe's latest series, output a pure sine wave that's cleaner than grid power. I'm not 100% sure on the industry-wide numbers, but in our testing at GoodWe, the THD (total harmonic distortion) on our 12kW three-phase inverters is under 3%. A cheap rotary converter? You're lucky to see 10%. That means your electric motor runs cooler, lasts longer, and needs less maintenance.

I still kick myself for not recommending this to a client back in 2022. They spent $6,000 on a static converter, paid $800 in installation for a dedicated 100A breaker, and still had issues with voltage sag on startup. If I'd recommended a 48 volt lithium battery price matched with a high power inverter, they could have had a backup power source for the same money. The cost breakdown in early 2023: a 10kW static converter was roughly $2,500. A 10kW solar hybrid inverter was $2,800. Adding a 5kWh battery (around $1,200 at the time) for $1,500? The inverter solution was actually cheaper for the 'whole system' benefit. And you get solar integration.

The most frustrating part: I still see installers recommending a transformer converter for a customer who has a micro on grid inverter system. It's a step backward. You're creating a new inefficiency. If you have solar, you want to use it to run the three-phase load. A transformer converter does not take DC power. You're buying a 50Hz box of wires that can't talk to your new EV charger. An inverter can.

Now, let's talk about the solar panels to run AC unit problem. An air conditioner is a motor load. It's almost always the hardest load on a system. A typical 3-ton AC compressor needs a 3.5kW run and a 10kW startup surge. Most people assume they need a massive transformer. You don't. A 7.2kW inverter with a 14kW peak for 5 seconds can handle that pullout torque with no problem. The secret is the surge capacity of the inverter vs. the derated capacity of a transformer. Transformers are oversized to handle the surge. Inverters can handle it natively. So a 7.2kW inverter can often do the job of a 15kW transformer, at half the price and one-tenth the weight.

That said, there are exceptions. If the load is a large-scale grid-tied project requiring strict grid code compliance (like in some parts of Europe where the grid code demands an isolation transformer), you'll still need a transformer. But that's a regulatory requirement, not a performance one. Also, for a perfectly sinusoidal output for lab equipment or medical devices, a top-tier inverter is still not a true line-frequency transformer. You might need a line filter, which adds cost.

I wish I had tracked the 'converter vs. inverter' savings across all our projects more carefully. What I can say anecdotally from the 50-odd projects I've coordinated: the inverter path is more reliable, faster to install (typically a 4-hour job vs. a 2-day job with a transformer), and has a lower total cost of ownership. The average cost savings in 2024 for a 10kW system was around 35-40% when you factor in labor and the battery backup benefit.

If I could redo one thing, I'd build a simple ROI calculator for our dealers. The math is simple: Transformer cost + installation + 2% efficiency loss over 10 years vs. Inverter cost + battery (optional) + solar credit. Usually, the inverter wins. Take this with a grain of salt because I'm looking at it from a solar-ecosystem perspective, not a standalone shop. But if you are in the solar business, combining a high power inverter with a 48 volt lithium battery to create a three-phase system? That's not just an alternative. It's the better standard.