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What does amperage mean in the electricity supply for my new home



Ok, so you’re in the process of getting all the nitty gritty sorted for your new home, and then suddenly the builder says that there’s not going to be enough electricity to power the home. Really? you say. So then you start enquiring and hit this question – ‘what does amperage mean in the electricity supply for my new home?’. Because that’s mostly where the problem will be.


Well, let’s have a crack at trying to demystify it for you. Which will be interesting seeing as we’re not electricians, but then again, it might be a good thing to put it in layman’s terms!


The first thing to understand is that electricity is made up of more than one characteristic. Without going into too much detail, there’s the voltage and the amperage (there’s also wattage, but we’ll leave that for later). 


Think about a water tank and pump – there might be a really powerful pump that provides lots of pressure, but it can’t suck enough water in for it to work properly. That would be like lots of voltage but not much amperage. Or it might have a big outlet from the water in the tank into the pump but only a tiny pump – the reverse happens, lots of amperage and not much voltage.


So voltage is like the ‘pressure’ of the electricity, whereas amperage is the sheer ‘volume’ or amount of electricity flowing.


Another analogy that some scientists have used is like a river. Steep and narrow is like high voltage and low amperage – it flows fast but there isn’t much water. It has less potential to kill you than a larger river that’s flowing slowly which is like high amps and low volts.


So the power wholesaler provides a service of supplying electricity to your property to run your home. And their service isn’t just open-ended where you can have as much power as you want – worse luck! They’re very specific in what they provide, and while you (or your electrician / builder) can discuss the needs with the power wholesaler at the initial application stage, they may not be able to provide the service you need. Why? Because they may not have the infrastructure available to carry the electricity you need – things like cables and transformers. More on this shortly.


We mentioned in the last paragraph ‘ … the service you need’. But what do you actually need? So the next step is fairly straightforward – it’s looking at the things in and around your home that need electricity. Easy. But then what items need lots of electricity? This is where the amperage comes in – the ‘volume’ of the electricity needed (we’re not talking about volts right at the moment).


Now, to drill into the detail, the first thing is to not worry about the smaller items. These are things like lights, powerpoints that are running things like computers, lamps, charging stations, etc. Focus on the big items. And in particular, focus on the things that have elements.


So what’s an element? It’s a part in an electric appliance or unit such as a heater, kettle, hot water service, or cooker which contains a wire through which an electric current is passed to provide heat. And this requires a lot more electricity than many other things. So, in principle, the big items will be your hot water service, air-conditioner, fridge and oven / cooktop / cooker. But even then, a lot of these items will be comfortably under the threshold of electricity supply to your home. So where is the problem then?


This is where you have to get a bit granular. Stick with us. Thanks.


Let’s talk data for a minute. Say your electrician says that the power wholesaler can offer a 40 Amp supply to your property. Now let’s look at your hot water service. For the purposes of this exercise, let’s say it’s a Thermann 315 litre electric unit. This is a 3.6KW unit. Ah, righto, here’s where the watts come in! 3.6kw is 3600 watts. And here’s the formula: total watts divided by the voltage = the amperage needed to run the unit. And remember that the volts available is always 220 ~ 240 (big story behind this but not for this blog). So let’s do the math:

3600 / 230 = 15.6 amps.


Ok, cool – the hot water service romps it in, well under the 40A supply for the home.


So where’s the problem then? Well, just keep looking. And you might find it in an induction cooker as an example. Take this one – a beautiful Fisher Paykel induction 900mm wide cooker unit. But! – it pulls more than 15,000 watts. Which equals well over 60 amps (67 amps to be precise) needed for the unit. So there’s the problem – that induction cooker!


But what can you do about it?


Well, there’s three things to think about.


The first is whether you can go back to the power wholesaler and ask for more power. They may have the infrastructure needed to be able to give it to you and then the problem would be sorted. Easy. But unfortunately not common, especially in rural areas. And even in newer areas, the power wholesalers are limiting the supply to 40 amps as a standard thing. So what next if they say no?


Consider a different cooker. Pretty obvious solution, but often disappointing as you’ve got your heart set on that particular unit and it was going to be so good. But you might find something out there very similar that has a lower power usage threshold and will satisfy you.


And third one is a compromise. Let’s say that you go back to the power wholesaler and they can increase it to 60 amps. Still short of the 67 amps needed for the cooker though!? But the other thing to realise is that there are 5 different elements within the cooker that are drawing on that power. So the 67 Amps is calculated when all 5 are on. Which is highly unlikely, in fact almost impossible. So 60 amps would be ok. You’d just have to realise that you can’t have the oven on, with the 4 cooking zones at the top also all turned on, because then you’d run out of power and …


Which brings us to the final comment. What we’ve explained here is fairly simplistic, and there are so many more factors to it, such as what other items are also running at the same time within the home; power fluctuations during peak times; how many phases your property supply has, etc. But you now at least get the principle of it and will be in a position to talk it through with your tradespeople to get the best outcome for you.


In fact, sometimes, you may not even know that you don’t have enough power at your property – your electrician or builder may not think about it, and may forget to tell you. So it’s a good thing – even if you don’t know of a problem – to ask them and make sure everything will stack up.


And as always, feel free to chat to us for more information.


Disclaimer. This blog is our opinion only. The information provided in our blogs is accurate and true to the best of our knowledge, but there may be omissions, errors or mistakes. The information presented in our blogs is for informational purposes only and we are not professionals, so the content we provide shouldn’t be taken as legal advice. We strongly recommend consulting with a professional before taking any sort of action. We reserve the right to change how we manage our blog and we may change the focus or content at any time.

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