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Posted 15 Jul
When it comes to talking about electricity, many use the terms 'power' and 'energy' interchangeably, but did you know these actually represent to different elements? It is important to understand these 2 terms, especially if you're looking at investing in solar, battery storage, or electric vehicles and their charging.
To summarise the difference between power and energy, power is simply the rate of electricity, where energy represents the amount of time that power is being used.
Power refers to the rate of electricity - the amount of electricity transferred at any single point in time. Electrical power is measured in Watts (W), Kilowatts (kW), and Megawatts (MW).
The term Power is mostly used in determining the amount of energy an appliance can consume or produce at a single point in time. An example could be a 10kW solar system, which its size is determined by the amount of power it can produce at its peak. A kettle will consume around 2-3kW of power to boil water.
Energy refers to the amount of electricity used over time: Measured in Watt-hours (Wh), Kilowatt-hours (kWh),
and Megawatt-hours (MWh), energy looks at the amount of power over a period of time - in this case an hour.
Energy is used for measuring an appliance's consumption over a period of time, so using the kettle example of 3kW power, over an hour, it would consume 3kWh of energy. 3kW × 1h = 3kWh.
When comparing Kilowatts and Kilowatt-hours, you're comparing power and energy.
Kilowatts (kW), or power, is how we measure the rate of the appliance production or consumption. Kilowatt-hours (kWh), or energy, is how we measure the amount of power over time.
Using the solar example from before, the system has a 10kW power capacity, which can generate up to 40kWh daily on average. This is calculated by the system capacity (kW) x sun exposure time which we summed up to 4.
10kW (power) system x 4 hours = 40kWh (energy) per day.
Both power and energy are used for all scales of devices and appliances to accurately determine the kW and kWh specifications. Watt-hour
is generally used for small appliances like phone batteries, where kW is mostly used for home appliances and solar systems,
and GWh being used for measuring coal power station yearly electricity production.
W = watt
kW = kilowatt (1000W)
MW = megawatt (1,000,000 W)
GW = gigawatt (1,000,000,000 W)
TW = terawatt (1,000,000,000,000 W)
Wh = watt-hour
kWh = kilowatt-hour (1000Wh)
MWh = megawatt-hour (1,000,000 Wh)
GWh = gigawatt-hour (1,000,000,000 W)
TWh = terawatt-hour (1,000,000,000,000 W)
If you're wondering why we measure energy and power differently, both serve separate purposes for understanding and working with electricity. By measuring power, you can identify elements like production rates which can be important for designing and installing electrical systems.
For example, identifying the maximum power rating for a solar inverter or home appliance can mean the difference between safe operation or overloading circuits or equipment.
Measuring energy on the other hand helps identify how much electricity is being consumed or produced over time. It can also help shape what kind of system is right for you, taking into account cost, efficiency, and suitability over time.
Overall, measuring energy and power enables utility companies, electrical engineers, and customers better-plan systems to avoid safety issues, over and under supply, inaccurate bills, and energy waste and inefficiencies.
Power is used for systems like solar, EV chargers, and inverters, where energy is primarily used for energy storage, bills, and household
consumption. Here's a list of what is measured by power and energy.
POWER (kW) |
ENERGY (kWh) |
| Solar Panels |
Battery Storage |
| EV Chargers | Electricity Bills |
| Solar Inverter |
Electric Vehicle Range |
| Generator Power Output | Daily Solar Production |
| Grid Connection Limits |
Feed-in-Tariffs |
| Power Ratings | General Household Consumption |
| Battery Charge/Discharge Rate | Backup Battery Duration |
So we've looked at power and energy in appliances and solar systems, but how does power and energy relate to electric vehicles? Using EVs as an example, we're met with an abundance of places where both power and energy are used.
Firstly, every electric car battery is measured in energy or kilowatt-hours, like how the BYD Sealion 7 has an 82.5kWh battery capacity.
This is not to be confused with phrases like '390kW of power'. This isn't referring to the battery capacity, but instead the power that the electric motor can output at its peak.
When it comes to electric vehicle charging, chargers are measured by power or kilowatts that refer the amount of power the charger can deliver to the battery. Chargers can range in power outputs, depending on AC or DC, however home AC chargers are usually 7-22kW depending on if your home is single or three-phase.
Electricity bills are measured in kilowatt-hours (kWh) as it refers to the total amount of energy you consume over time - usually each quarter. Energy providers look at both the amount of power consumed, and the duration it is consumed for.
Additionally, you'll notice solar feed-in-tariffs are also measured in energy. This is to determine the amount of power you produced over an amount of time.
If you have a solar battery like Tesla Powerwall 3, it will have a total energy capacity which will in this case consist of 13.5kWh of energy, meaning if you're drawing 6.75kW of power from the battery, it will last 2 hours.
If energy providers were to determine your bill based on power consumption, they would only be able to see the amount of power you're drawing at any given moment. Using energy is essential to finding out how much power a home or business has consumed over an amount of time to accurately bill based on usage.
Both power and energy are essential to measuring electricity and component specifications throughout Australia, and can also help you understand your energy better.
Whether you're interested in getting a solar and battery system, you're a new electric vehicle owner, or just an avid reader looking to increase your electrical knowledge, you now know what the difference between energy and power is.
For more information and Newcastle and Maitland-based solar and battery installations, please get in contact with us.
Below are some frequently asked questions about power vs. energy and kW vs. kWh.
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