Understanding Electrical Basics: Volts, Amps, and Watts

When you’re working in HVAC—especially with systems like MRCOOL’s mini splits—understanding how electricity works isn't just helpful, it's essential. Whether you're sizing up a generator, troubleshooting a unit, or explaining power needs to a customer, knowing the difference between volts, amps, and watts will give you a serious edge.

Let’s break it down in a way that actually makes sense.

🔋 Volts: The Push

Voltage (V) is the electrical pressure that pushes electricity through a wire.
Think of it like the water pressure in a hose—the higher the pressure, the harder it pushes water through.

• High voltage = more push

• Most residential systems are either 115V or 230V

• MRCOOL DIY mini splits, for example, can come in either voltage depending on the model

👉 Remember: Voltage is usually set by the power supply and not adjustable on the unit.

🔄 Amps: The Flow

Amperage (A) is the amount of electricity flowing through the system.
In the water hose analogy, this is how much water is flowing per second.

• Larger appliances (like compressors) typically draw more amps

• The more amps something uses, the thicker the wire needs to be

• Overloading a circuit with too many amps = tripped breaker or potential hazard

👉 You’ll often hear techs say things like “That unit pulls 12 amps”—they're talking about how much power it's drawing during operation.

💡 Watts: The Work Being Done

Wattage (W) is the actual power being used by the system.
It’s what’s doing the work—running the fan, compressing refrigerant, heating the air.

The formula is simple:

Watts = Volts × Amps

So, if you have a 115V system drawing 12A:
115 × 12 = 1,380 watts

That’s how much energy the unit is actually using when it’s running normally.

⚙️ Real-Life Example: MRCOOL DIY 18k BTU Mini Split

• Voltage: 115V

• Amperage: ~12A

• Wattage: ~1,380W (running)

• Surge Wattage: Could briefly spike to 2,000+W when the compressor kicks on

Knowing these values helps you:

• Choose the right circuit breaker

• Size a generator properly

• Prevent overloads

• Understand energy consumption

🔌Circuit Breaker Sizing Basics

⚠️ Breakers should typically be rated for 125% of the continuous load.
So if a unit draws 12 amps continuously, you'd want a 15A breaker minimum, often rounding up to 20A to account for startup surges.

🧯Safety Notes:

• Undersized wiring or breakers can overheat and become a fire hazard.

• Always match the wire gauge to the amp load.
  (e.g., 12-gauge wire = up to 20 amps, 10-gauge = up to 30 amps, etc.)

🧊 Power Factor

In AC systems, not all the power drawn is used efficiently. The Power Factor helps calculate real power vs. apparent power. For most residential units, it’s close to 1, so we don’t worry too much—but it matters more in large commercial setups.

🛠 Why This Matters in HVAC

• Installers need to size wire and breakers based on amps.

• Customers want to know how much power a unit uses (watts).

• Troubleshooting often involves checking if amps or volts are off.

• Generators and backup systems must account for surge wattage, which is usually higher than the running wattage.

🧠 Final Takeaway

Understanding volts, amps, and watts helps you speak the language of electricity—and that makes you a smarter, safer, and more confident technician.

So next time someone says, “How many amps does that unit pull?” or “Will this trip my breaker?”, you’ll have the answer—and the knowledge to back it up.