That's what Powerswitch does, shows you the calculations for various suppliers.

You can calculate it yourself if you want, it wasn't too hard when I done it very recently.
Find out the power usage for the period you want to calculate, multiply your usage by the rate your supplier charges per kWh (add the levy if that's separate, some suppliers include that in their unit pricing so make sure to check), add the daily charge for the days in that time period, and add GST/subtract any discounts. 

I tried Powerswitch and it doesn't do this.  What it does is calculate what it thinks your yearly charge will be for your current supplier, and various others citing the savings. 

If you want to get rates for various suppliers, it's very difficult.

Eg.  I went onto Electric Kiwi's site, and it's not clear what the various rates are. 

Did you put in the whole 12 months of usage like it recommended? It only estimates your usage if you don't provide it. 

Also re: Electric Kiwi their site seems pretty clear, click Pricing at the top, enter address, pricing is shown. Click "pricing options" below it to change between the plans and tiers. Most companies are the same. 

I tried PowerSwitch again and for my address, and for EK it says 

Anytime Variable charge:$0.2992

Daily Fixed Charge:$0.3700

I presume these include GST.

Now if I go to EK's site it says:

 

•  

   

  • Pay for what you use: $0.2733 per kWh;
  • Plus a fixed cost of: $0.3400 per day

   

   

   

   

The latter is GST inclusive and includes a 1 year commitment for a low user plan.

So, I see different pricing.

Check that the plan is the same. I just compared PowerSwitch and Electric Kiwis site and was able to get the same pricing. On ElectricKiwis site I had to select GST inclusive, lower user on 200 pay ahead plan for my case. When I re-checked power switch the same plan details was listed as well just below the supplier name/logo. 

Forgot to mention as well, just make sure you're checking the usage type as nearly all suppliers will have a lower user or standard user rate. 
In both cases the low user rate has a lower daily charge but a higher kWh cost. The standard user has a higher daily charge but a lower per kWh cost. 
If you use over 8000kWh/year you should be on a standard plan. 

Seems to be prepaying power but you get a bonus each time you "topup", and you have to prepay 200 each time from what I gather. I can't tell who they're trying to market towards with that one?

I found the best site to use is https://www.switchme.co.nz/

It is also better to use “I have my Bill” option (if you have a bill) rather than the other as the other just compares others around your area which in my case inflates the price too much.

After selecting that option just enter your ICP number and then click “Search” After your address appears enter the Usage details from your bill and click “Go”

A range of Power company prices will then appear. Just hover over the “i” to get their unit prices.

You can also hover over other “i” for other details including discounts etc.

Often if you go direct to a Power Supplier they will not give you their best price. I tried Meridian and they quoted me an “All Inclusive” (I think that was what it was called) but I already knew of their “Super Saver” plan that was cheaper. They did come back and then say they would do the “Super Saver” plan. Deceptive.

I actually made up an Excel Spreadsheet some years ago and then expanded it so I can compare up to 6 Power Suppliers after getting the Unit prices from Switchme.

You just enter the Usage, Days, Unit Price (including EA if shown in Unit Price, Discount, any Line charges (most seem to include them in the Power Company price now), Company Name and Plan, and Excel will calculate them. The results are within 1-2 cents of the price shown on the Switchme website

I found it easier then to change the Usage in the Excel Spreadsheet for different months of the year so you can contemplate, cogitate, speculate, which is the best Power Supplier for you.

I found it was not worth changing from Mercury as I was already on a valued Customer Discount (an extra 10% plus the usual 12%) though I had to threaten to walk if I did not get it as I had it for the previous 2 years and they were going to take it away from me on my new contract in February this year(no longer a valued customer BooHoo)

gchiu: What exactly is the 200 pay ahead plan??

So, the stay ahead plan seems to be 10% more expensive than the loyal kiwi plan but then they discount the payment by 10% so maybe you end up equal except you don't have to pay cc fees?

I'm going to play with the switchme site.

And switchme suggested Contact as cheapest instead of EW suggested by Powerswitch with both given the same data.

I don't understand why some providers (and I'll target Electric Kiwi since they're discussed in this thread) continue to confuse customers by advertising prices that by default excl GST. Their target market is residential users, 100% of whom have to pay GST on their electricity, and the only reason I can think of for continuing to do this is to confuse people who look at other retailers that do include GST in their pricing.

They should all follow a standardized way of reporting their pricing.  GST exclusive is bizarre.

I got caught by the non GST power pricing a few years ago.

Salesman arrived at door offering a "good deal" to shift. He said all charges were included in their price and there was a 10% discount for paying on time. Also a $50 new customer bonus. Price was better than current supplier, so took up his offer.

Changeover went smoothly with no problems.

First bill arrived and I see that GST was not included in their "special pricing". Worked out to be slightly dearer than we were paying. Rang company for explanation and was advised that GST is not included in their pricing, and I must have misunderstood the salesman.

Soon as $50 was used up I switched to Genesis, and been with them ever since. Very happy, and haven't found anyone that can beat their pricing or service.

Any salesman that is silly enough to knock on the door gets escorted to the gate and shown the bright red DO NOT KNOCK sticker on the mailbox. Now also have a sticker on the front door, and haven't been pestered since.

k1w1k1d:

I got caught by the non GST power pricing a few years ago.

Salesman arrived at door offering a "good deal" to shift. He said all charges were included in their price and there was a 10% discount for paying on time. Also a $50 new customer bonus. Price was better than current supplier, so took up his offer.

Changeover went smoothly with no problems.

First bill arrived and I see that GST was not included in their "special pricing". Worked out to be slightly dearer than we were paying. Rang company for explanation and was advised that GST is not included in their pricing, and I must have misunderstood the salesman.

Soon as $50 was used up I switched to Genesis, and been with them ever since. Very happy, and haven't found anyone that can beat their pricing or service.

 

Any salesman that is silly enough to knock on the door gets escorted to the gate and shown the bright red DO NOT KNOCK sticker on the mailbox. Now also have a sticker on the front door, and haven't been pestered since.