Energy is the capacity of something to do work. The technical bit for those that are interested:Įnergy: Energy is measured in Joules. If they get this wrong how on earth are they gonna understand your requirements? A lot of cold calling door knockers will fail this test in my experience. Top tip for filtering out the worst solar and battery salesmen: Ask them to explain the difference between a kW and kWh. In other words, the more power it has, the more appliances you can power with it and the more energy it has, the longer you can power those appliances.įor normal household use, you want enough energy to get you through the night and at least 5 kW of power for speedy charging.
The more energy (kWh) a battery has, the more you can store and the longer it will last, the more power it has the faster you can get that energy in or out of the battery,
#Kwh to kw conversion full#
At full power, then, it can fully discharge in under 3 hours. Its power is 5 kW, so it can charge or discharge at that rate. The battery’s energy storage capacity is measured in kWh-for example, the ‘Powerwall 2’ stores 13.5 kWh of energy. When buying batteries, you need to think about both the power of the battery and the energy storage capacity of the battery you are looking at. If you do, you may end up with a solar system that is completely the wrong size! How do kW and kWh relate to batteries? If what they actually meant was that they need one to cover an energy usage of 12 kWh per day, they really need a 3 kW solar system that costs about $3,500 at the time of writing! If a buyer has studied their energy consumption and carelessly says they need a solar power system to produce 12 kW, they might end up being quoted a 12 kW solar power system, which will cost about $10,000 at today’s prices and produce about 48 kWh per day. Well, it is actually quite important if you are buying a solar system. Yeah, yeah I know what you are thinking: Who cares? They probably really mean that they used 8 units of electrical energy yesterday, In which case they should have said It drives electrical geeks like me up the wall, especially when I read it in national newspapers and books!įor example: If someone is talking about their electricity usage and says: Most people do it all the time without noticing. It is very common for people to mistakenly interchange the terms energy and power as if there is no difference.
Why is the difference between Energy and Power important? So at the highest level: kW measures power, and kWh measures energy. “My solar system produced 4 kWh of electricity today!” The amount of electricity you use (or generate) is defined in kWhs. If your solar panels (for example) continuously output 1 kW of power for a whole 60 minutes, you will have produced 1 kWh of energy. A kWh is a measure of energy (not power). a 3 kW system can produce 3 kW of power at solar noon (when the sun is at its strongest) on a perfect solar day:Ī 3 kW solar system can produce 3 kW of power at around midday on a perfectly sunny day. Peak power defines a solar system’s size. Notice that, if you like to keep anal electrical engineers like me happy, the correct way to write it is always with a small k and a capital W. So kW means kilowatt, which is 1000 Watts. H stands for hour, which is obviously a measure of time. W stands for Watt, which is a measure of power. Let’s start with what each letter stands for. So here is my humble attempt to answer the question: What is the difference between a kW and kWh? Please excuse this post if you think I am explaining the bleeding obvious! But I think it is vital to write a post that describes these key units of electricity in a way that requires zero prior knowledge of anything electricity-related. I’ll deal with that doozy in this footnote 1. What do they stand for? What do they mean? And what’s the difference between the two? Watch the video, or read below to find out…įolks who are really confused also throw the term “ kilowatt/hour” into the mix. One of the most common sources of confusion I encounter when talking to non-electrical people about solar power is related to the terms kW and kWh.
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