Power Units Explained: Watts, Kilowatts, Megawatts and Their Conversions

Solar power, battery storage, and other home energy solutions empower people to take control of their energy consumption and slash electricity bills. However, as you explore and exploit these systems, you may come across a variety of key terms that measure the quantities of power such as Watts (W), Kilowatts (kW), and Megawatts (MW). 

Understanding the meaning behind these power metrics as well as how they can be converted unlocks the full potential of your energy efficiency strategy, leading to bigger savings and greener footprint. 

What are Watts, Kilowatts, and Megawatts

Watts

A watt is a power unit that measures how fast energy is consumed or generated. Think of it as a speedometer for energy consumption. For instance, a light bulb rated at 10 watts burns through 10 joules of energy per second to light up your space (1 W=1 J/s). This means the higher the watts, the more energy it takes to power the device, which translates to more electricity consumption at a given period of time.

A typical LED light bulb might use 10 watts, whereas a traditional 60-watt incandescent might guzzle much more energy to produce the same level of brightness.

Kilowatts

1 kilowatt is equivalent to 1,000 watts. It’s usually used to describe the power of larger electrical appliances or systems. For example, a home water heater rated at 5 kilowatts draws 5,000 watts of power when it’s running. In practical terms, kilowatts help us compare the power needs of devices, assisting in making smarter, energy-efficient choices, like switching from an old 2000-watt clothes dryer to 1200-watt heat pump dryer, saving both power and energy over time.

kW vs kWh

While kilowatts (kW) and kilowatt-hours (kWh) look almost identical, they are entirely different in what they measure. 

Kilowatt measures power, or how fast electricity is being used or generated in the moment. You can draw an analogy between Kilowatt and the "speed" at which energy flows. On the flip side, kilowatt-hour tracks the total energy you’ve used over a period, typically for billing purposes. It’s like measuring how far your car has traveled. If you run a 1 kW device for one hour, it will consume 1 kWh of energy. So kW vs. kWh is about immediate energy demand to run a device vs. cumulative consumption. 

Scale up the Unit to Megawatts and Gigawatts

Megawatts (MW) and Gigawatts (GW) quantify power on a much larger scale, far beyond the level of a household.

Megawatts (1,000,000 watts) are typically used to measure the output of small to medium power plants or large renewable energy installations like solar or wind farms. 

Gigawatts (1,000,000,000 watts) are often used to describe the capacity of large power plants or national energy grids.

The Mammoth Solar project in Indiana, set to become the largest solar farm in the US, for example, will have a capacity of up to 1.65 GW. The first phase, Mammoth North, includes a 400 MW capacity which produces enough energy to power 275,000 homes.

kW to MW Conversion and Vice Versa

The conversion from kW to MW is a simple math. To get MW, simply divide the kW value by 1,000, and to get the vice versa, multiply the value of MW by 1,000. For example, a 500 kW solar installation would generate 0.5 MW of power, a more appropriate unit to describe large scale energy production. 

kW to MW Quick Conversion Table

How Many Kilowatts Does A House Use?

To determine the number of kilowatts your house is using, you’ll need to know the number of kilowatts it takes to power your home gadgets. Here’s a breakdown of how much power, in kilowatts (kW) you need to keep your appliances humming along. 

Kitchen Power-Hungry Essentials

• Microwave: 0.6 to 1.0 kW
• Refrigerator: 0.3 to 0.8 kW
• Oven/Stove: 2.0 to 5.0 kW

Living Room—Low Energy, Big Comfort

• TV: 0.05 to 0.2 kW
• Light Bulbs: 0.01 to 0.06 kW

Heating & Cooling—Biggest Energy Hogs

• Heat Pump: 0.545 to 7.5 kW
• Space Heater: 1.5 kW
• Central AC: 3.0 to 4.0 kW
• Window AC Unit: 0.5 to 1.4 kW

Laundry Power—Clean Clothes, High Wattage

• Washing Machine: 0.4 to 1.4 kW
• Dryer: 1.5 to 5.0 kW

Miscellaneous Devices—Little Helpers, Big Impact

• Computer: 0.03 to 0.07 kW
• Phone Charger: 0.005 kW
• Wi-Fi: 0.005 to 0.02 kW
• Hair Dryer: 1.5 to 2.0 kW
• Electric Vehicle Charger: 7.2 kW
• Treadmill: 0.6 to 0.7 kW
• Peloton: 0.05 kW

Note: The listed appliances are assumed essential appliances for references. The real kilowatts need for home vary depending on the size of the house.

How Many Solar Watts Do I Need?

To figure out how many kilowatts of solar panels you need to power your home, you should first assess your household’s energy consumption, measured in kilowatt-hours (kWh). On average, a US home consumes about 10,632 kWh per year or 886 kWh per month, which means your home’s daily energy consumption is:

886 kWh/30 days = 29.53 kWh

If you’re aiming to meet all your energy needs with solar, you’ll need a solar system capable of covering that consumption.

Using an average of 4 hours of peak sunlight per day, you can estimate the size of your solar system using a simple formula:

29.53 kWh/4 hours=7.38 kW

This means you’d need a solar system that produces 7.38 kW power to support electricity needs.

Note: The calculation is based on average household values. If your home includes high-power loads such as EV, you may need to refine your estimates by factoring the additional consumption.

How Many kWh Battery Do I Need for Home?

If your house is equipped with solar panels, it can cover around 50-70% of your daily usage. Except for 24-hour backup, a home battery often needs to cover one-third of the daily energy consumption, which, according to the average daily consumption mentioned earlier (29.53 kWh/day), will be:

29.53 kWh/3 = 9.84 kWh

Considering that most battery systems have a conversion efficiency rate of about 90%, the required battery capacity should account for some energy loss during conversion. To meet this demand, your battery system should have a capacity of at least:

9.84kWh/0.9 (efficiency rate) =10.93kWh

This means a battery system with a capacity of around 11 kWh is ideal for covering essential loads. 

The FranklinWH aPower 2 lithium iron phosphate (LFP) battery, with a capacity of up to 15 kWh per unit, can easily meet the needs of your entire home during an outage, peak period, or when you want to be 24/7 off-grid, providing enough energy to power all essential loads without interruption. 

Final Thoughts

Optimization of energy efficiency requires high proficiency in power and energy estimation. Grasping the meaning of key power metrics helps enhance your skill of managing energy solutions such as solar system, home battery, and other more advanced systems, allowing you to make smarter decisions of load shifting or load shedding to lower energy bills based on these estimations.