{"id":81360,"date":"2024-02-08T07:50:55","date_gmt":"2024-02-07T22:20:55","guid":{"rendered":"https:\/\/www.solarquotes.com.au\/blog\/?p=81360"},"modified":"2024-02-08T07:50:55","modified_gmt":"2024-02-07T22:20:55","slug":"explaining-kw-kva-power-grids","status":"publish","type":"post","link":"https:\/\/www.solarquotes.com.au\/blog\/explaining-kw-kva-power-grids\/","title":{"rendered":"Pint Glasses to Power Grids: Explaining kW and kVA"},"content":{"rendered":"

\"beer<\/h3>\n

Electrical devices have many different ratings, but one of the most confusing distinctions for the average consumer is between kilowatts (kW) and kilovolt-amperes (kVA).<\/p>\n

<\/p>\n

Kilowatts vs. Kilovolt-Amperes: Decoding the Jargon<\/strong><\/h2>\n

Half of humanity confuses the relatively easy-to-explain kilowatt-hours<\/em> with plain kilowatts (you’ll find some good references<\/a> here for kWh vs kW<\/a>).<\/p>\n

But hold onto your hat, because the concepts I’m explaining below are a bit more abstract.<\/p>\n

The classic trade-school explainer on kVA and power factor involves a pint of beer. The useful part is the glorious amber liquid you can drink \u2014 that’s active power. But on top there is always that white foam; simultaneously useless and indispensable \u2014 that’s reactive power.<\/p>\n

If you’re now confused and<\/em> thirsty, don’t worry. I assure you most apprentices are too. But bear with me while I try to draw a picture with words.<\/p>\n

(And if you’re an electrician, retired engineer or similar pedant, please go easy in the comments section. We’re here to help the punters.)<\/p>\n

Calculating Kilowatts<\/strong><\/h3>\n

Getting a handle on kilowatts isn\u2019t too hard, we’ve run through it before with a simple ohms law calculation.<\/a><\/p>\n

    \n
  1. Take the ordinary mains supply of 230 volts (this is the pressure that drives an electrical circuit).<\/li>\n
  2. Multiply 230 by the amperes required (the measure of current, or flow of energy needed by the device).<\/li>\n
  3. For 8.7-amps, for example, the result is 8.7 x 230 = 2,000 watts, or 2kW.<\/li>\n<\/ol>\n

    This would be enough energy to run a fan heater, kettle, toaster or small, conventional hot water service. These are simple resistive loads<\/strong>, just like a bathroom heat lamp.<\/p>\n

    Other similarly heavy loads could include a pool pump, air compressor or split-system air conditioning unit. However, these are inductive loads<\/strong>. They have large inrush currents, so they’re difficult to start. They also react with, and cause distortion on, the mains supply.<\/p>\n

    That reaction or distortion has a separate rating: power factor<\/strong>.<\/p>\n

    Kilowatts (kW)<\/strong> represent the actual active power used for doing useful work.<\/p>\n

    Kilovolt-Amperes (kVA)<\/strong> refers to the apparent power. That is, the working power plus the reactive power factor \u2014 which does not do the useful work, but is necessary to maintain the voltage levels in the system.<\/p>\n

    Real-World Applications of kVA and kW<\/strong><\/h3>\n

    In practical terms, most people aren\u2019t aware of the differences between kVA and kW until they go camping and want to buy an inverter or petrol generator for power. The local tool shop will have machines rated in kVA, and they\u2019ll sensibly advise buying more than you need.<\/p>\n