Difference between Power (kW) and Energy (kWh)
Posted: 25 Oct 2019
Power and energy, synonyms, right? Wrong! Especially when it comes to shopping around for a solar system or solar battery storage. The two words while interchangeable in some circumstances have two very different meanings and knowing the difference between the two will greatly assist you through the research and purchase stage of a solar system or the addition of solar battery storage.
In simple terms power is how fast work or energy is performed per unit of time or the amount of energy used per unit of time.
For example, a high-powered tap will gush out water fast, at a high pressure filling a bathtub quickly. A low-powered tap may dribble out the same amount of water but over a longer period, meaning you’ll have to wait for your desired soak in the tub.
The power of a solar system is the amount of electricity generated at a given moment. When mentioned in reference to solar or battery storage, power is measured in Kilowatts (kW), 1kW equalling 1000 Watts. This means a 5kW solar system has the capacity in peak weather conditions to push out 5kW of electricity. In not so peak conditions like morning, evening or overcast it may only push out 2kW at a given moment in time.
In reference to battery storage the kW power rating would be how much power can flow into or out of the battery in any given moment.
It’s important to note that a power rating does not cover the storage capacity of a solar system or battery, but only the instantaneous output.
Energy is the volume that electricity has been generated, stored, or consumed over time. When referred to in the solar industry, energy is measured in kilowatt hours (kWh). 1kWh is equal to one hour of electricity used at the power of 1kW. So, an appliance with a power rating of 2kW would consume 2kWh in one hour.
Over one day a solar system can generate several kWh from the sun. As an example, a 5kW solar system may produce up to 22kWh over an entire day. How many kWh were produced each hour would vary depending on weather conditions, shading and time of day however the accumulative for the day could be 22kWh.
You’ll notice your electricity bill will state the units of electricity used per day or quarter as kWh. This is helpful when trying to decide how much energy you will need from a solar system to cover the majority of your energy usage.
When referring to a solar battery, kWh are the quantity of energy a battery can store.
Energy and Power For Solar
Being able to distinguish the difference of kW (power) and kWh (energy) when speaking to solar providers and looking at solar systems or battery storage will be extremely beneficial in helping ensure you get the size system or battery required for your electricity usage needs.
These simple dot points will assist you in recalling the differences between the two;
- The maximum amount of power a system generates at a given moment is referred to as kW. So, a 5kW solar system can produce a maximum of 5kW at any one moment.
- The energy production of a system is referred to in kWh, so you may ask an installer how much energy they would estimate your 5kW solar system to produce or generate in a day, which they would respond in kWh.
And finally, this equation will hopefully makes calculating your household appliance usage much simpler!
kW (power) x time = kWh (energy).
Now that you understand the difference between Energy and Power you may be interested to see the estimated annual production of kWh that different sized solar systems can produce. Comparing this with the average energy usage on your electricity bills will assist you in finding the right size solar system for your household.
See our Residential Solar System Size page to view estimated prices and annual production or start speaking to accredited installers local to your area who can assist!
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