How we calculate your saving

1. What we read from your bill

Your postcode and network, the billing period, your usage (split into peak, shoulder and off-peak if your bill splits it), controlled load, solar exports, and your current rates: each usage rate, the daily supply charge and the feed-in rate. We also read the dollar amounts the bill prints for usage, supply, solar credit and discounts, and the total of new charges for the period. We never use the amount due, which can include past balances.

The same file always gives the same reading. The reader is an AI model, and AI models can answer slightly differently from one run to the next. So the first reading of a file is kept, and uploading the same file again returns exactly the same figures. You can also correct any figure before it's used.

2. Proving we read it right

Before showing any saving, we rebuild your bill for its own period: usage × your rates, plus days × your supply charge, plus controlled load, minus solar credit and discounts. Then we compare that with the total printed on the bill.

• Within 6%: we say we reproduced your bill, and show both figures.
• More than 6% out: we say so, show the gap, and ask you to check the figures. We never adjust a rate to make the sum close; a reading that adds up only because a number was changed would be worse than one that doesn't.
• Solar bills net a large credit against large charges, so the total can be small and a few dollars can look like a big percentage. We judge those in dollars as well.

3. Your year of usage

We add up every bill you've given us for the same home from the most recent 12 months. Bills for a different address are left out, and so are bills whose dates overlap (a quarterly bill and the monthly bills inside it would count the same power twice). The result is scaled to exactly a year: usage × 365 ÷ the days covered.

If you've given us one bill, it's that bill scaled to a year, which overstates a winter bill and understates a summer one. Your comparison always says how many bills the figure rests on, and adding more bills improves it.

If your usage changed sharply, say after a battery or solar went in, we compare on the bills since the change and tell you, with a button to use all your bills instead.

4. Pricing every plan

Plans come from the regulator's published plan data (the same source as the government's Energy Made Easy site), refreshed every night, for your distribution network. Each plan is priced on your year of usage:

• UsagekWh in each time band × that band's rate
• Supply charge365 days × the daily rate
• Controlled loadits kWh × its rate, plus its daily charge
• Solar creditexported kWh × the feed-in rate, by time band where the plan pays that way
• Discountsguaranteed discounts taken off; conditional ones only on the “best price” view
• Feesongoing plan or membership fees added

GST: the regulator publishes prices without GST. We add 10% to usage, supply and controlled load, as your bill does, and not to the feed-in credit.

Time-of-use plans on a single-rate bill: a single-rate bill can't say when you used power, so we apply a standard daily pattern. This is the biggest source of uncertainty for single-rate homes. Smart meter data, where you share it, replaces the guess with your real half-hours.

5. Which price we rank on

By default we rank on the guaranteed price: what you'd pay with no pay-on-time or direct-debit discount. Retailer sites usually lead with the discounted price, so their figure can look lower than ours for the same plan. You can switch the ranking to the best price (every discount earned) or the first-year cost (sign-up credits and one-off fees included).

6. The saving

Your bill for a year (your bill totals × 365 ÷ the days they cover) minus the plan's cost for a year on the same usage. If you've told us about a battery that went in after your bills, we don't credit the battery's effect to switching plans; we compare plans on the same battery-adjusted usage instead, and say so.

7. Plans we leave out

Plans you can't join aren't savings, so they're removed rather than shown: plans needing solar, a battery, an EV, a smart meter or a VPP you haven't told us about, minimum-usage plans you're under, and plans restricted to members, seniors or a particular sales channel. You control these in your account.

Why your own sum might not match ours

• Discounts: we lead with the guaranteed price; a retailer usually leads with the discounted one.
• The year: we use a year of your bills; a single bill scaled up gives a different number.
• The date: plan prices change, and we re-price every night.
• GST: a figure without GST is about 9% lower than one with it.
• Time of use: on a single-rate bill, the peak/off-peak split is an estimate.

If you still can't make a figure match, use “Is this right?” on the plan and attach your bill. Reports come to our accuracy review, and a confirmed error is fixed for everyone.

Check us yourself

1. Open “Check our working” above your results for the usage, bill and price basis everything rests on.
2. Open any plan for its line-by-line sum: quantity × rate = amount, for every charge.
3. Each plan shows the regulator's plan ID. Look it up on Energy Made Easy to check the rates against the official record.
4. Download the working as a spreadsheet and check every line offline.

How accurate it is

We measure how often we rebuild a bill to within 6% of its printed total. When we last measured, 58 of the 100 bills customers had uploaded rebuilt to within 6%. Many of the rest were read before our October 2026 improvements to reading bills from every retailer, and new uploads use the improved reader. When a bill doesn't rebuild, the customer is told and the saving is worked out from the bill's printed total. We publish this figure because we'd rather you knew.

Last measured 29 October 2026.

The detail

• How plans are actually rankedThe full costing model: every component priced against your own usage, and nothing else in the ordering.
• The reproduction check: proving we read your bill correctlyHow every bill is verified against itself, why it is allowed to fail, and what a failure means.
• Why some cheap plans never appear for youEligibility filtering: how plans you cannot actually buy are removed instead of dangled.
• How solar and batteries are modelledFeed-in bands, self-consumption, arbitrage, and the honesty limits applied to battery claims.
• How this differs from Energy Made Easy and commercial comparatorsAn honest account of what the free government tool does well, and where a paid tool earns its keep.
• What actually moves your bill (and why solar + battery flips it)How to work out which rate is worth shopping for on your own usage — and why the usual advice inverts once you have a battery.

Questions