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Part 2 of 4: What is 1 and 3 Phase? And No! We’re not talking phases of the moon!

In this 4-part series of articles Greg Shaw, Managing Director, Solar Shop Hua Hin, explains by KISS (Keep it Simple): The difference between DC and AC power; The difference between 1 and 3-Phase; How do Solar PV Panels Work?; and What is a solar inverter? Stay tuned as there will be more articles to come to help you (and our customers at Solar Shop Hua Hin) understand solar systems. If you take the time to read this 4-part series you will be rewarded with a real-life practical conclusion which you will more fully understand. And that will brighten you day because knowledge is power!

PART 2: What is the difference between 1 and 3 Phase?

written by: Greg Shaw, Managing Director, Hua Hin Solar Co., Ltd.

One of the first questions we ask of customers interested in solar systems is, ‘Is your property 1 Phase or 3 Phase?’ Most house, development or business owners reply, “That’s a good question. I’ll get back to you!”

But wait! What is 1 and 3 Phase anyway?

Both 1 and 3 Phase power systems are used throughout the world. 1 Phase or “single phase” is a two-way AC power circuit. Single-phase systems in Thailand use alternating current electric power in which the voltage and current flow changes in magnitude and direction in a cyclical fashion, typically 50 times a second or 50Hz. 1 Phase systems power lights and other household appliances such as TV, electronics and kitchen appliances. In the United States, 1 Phase power is 120V and in other countries (such as Thailand) around the world, it is often 220V as standard. It is important to note that in 1 Phase power systems all the loads run off a single phase power line. As current flow is higher in single phase lines the wires are physically bigger than three phase wire lines.

3 Phase is three-way AC power circuit. In three-phase systems, the power circuit combines three alternating currents that vary in phase by 120 degrees. The 3 Phase arrangement is equivalent to three 220V single-phase power circuits on 3 wires with a 4th wire (Neutral to Ground) present. New housing developments and businesses therefore use a 3 Phase 4 Wire 380V/50Hz because of its superior power carrying capability and flexibility all at a reduced cost. Three-phase systems can power low-power loads (lights), medium-power loads (water heaters) and high-power loads (heating, ventilation and cooling).

Moreover, appliances/devices (single phase) can be supplied by just 1 of the 3 Phase lines. If you spread the loads on the 3 Phase lines electricians would say that you are effectively “balance” the electrical system supplying power to your property – and that is a good thing. Finally, it should be noted some motor-type devices and heaters only run on 3 Phase.

A closing question: What are the main benefits of three-phase verses one-phase systems?

One of the main benefits 3 Phase systems is that the cost to install and maintain them is lower. This is because the systems use less conductor material – about 25 percent less for the same amount of power delivered. Three-phase systems deliver more power over a given time period than one-phase systems and the power delivered is almost constant, making them ideal for power grids, transmission lines and data centers.


Hua Hin Solar Co., Ltd., is Hua Hin’s largest and most dependable solar energy company. We provide exceptional products and services at affordable prices and we offer long-term customer care. Our Team is committed to using green solar and wind energy to help our retail customers and residential/business partners make the necessary transition towards energy independence. “We design and install affordable solar systems with the highest yields. For your free consultation contact us today at huahinsolar@gmail.com. If you have anything less than a great experience with Solar Shop Hua Hin please call my cell.” Greg, Managing Director, +66(0)89 824 1963.