How cost is calculated

Most electricity comparison tools use an average annual usage figure — say, 6,000 kWh — and multiply it by the plan’s headline rate. That is fast and simple, but it produces the same answer for a household that uses power at midday as for one that uses power at 11 pm. For time-of-use plans, the difference can be significant.

Nemity works the other way. It starts from your actual half-hourly interval readings — the raw data your smart meter records — and applies each plan’s rates to each interval individually. The result is the cost for your usage pattern on that plan, not the cost for an average household.

The Victorian Government’s own comparison tool, Victorian Energy Compare, also lets you upload your actual meter data and prices it against real time-of-use rates rather than a flat estimate (at least most of the time). But it has real limits: it gives you one annual total, with no season-by-season breakdown, and no way to enter your current plan’s rates to see exactly how much you’d save by switching. Nemity can price any window you choose — a single season, or the next 3 or 6 months. A season is priced on its most recent occurrence in your data, and a forward window on the same dates one year back: the assumption is that the year ahead resembles the year you had, and a period with days missing is flagged rather than assumed complete. It can also model a home upgrade you are considering — solar, an EV or a battery — and estimate what every plan would cost with it. That estimate could be wrong; the meter has never recorded the upgraded home. But it is built from your own half-hourly usage rather than an installer’s assumed household patterns, and it works as a guide to which kinds of plans suit the upgrade — not as a forecast of a bill.

Your electricity meter records usage in 30-minute intervals, 24 hours a day. A full year of data is 17,520 readings. Nemity reads and processes all of them in your browser — nothing is sent to a server.

Supported formats include NEM12 files from all five Victorian distributors (CitiPower, Powercor, AusNet Services, Jemena, and United Energy), plus the AGL My Account, Origin and Jemena My Portal usage exports, and some other formats. Files with 5-minute or 15-minute intervals are aggregated into 30-minute intervals before pricing.

For households with solar, the meter records export intervals separately (channel B1). Nemity reads both import and export channels.

Plan data comes from the AER Consumer Data Right (CDR) Product Reference Data feed — the same source underpinning Victorian Energy Compare. It is refreshed weekly. Rates are carried at full precision (3–6 decimal places) throughout the calculation and rounded to cents only at the final output.

For each plan, the calculation adds up:

• Supply charge — a fixed daily charge, multiplied by the number of days in your comparison period.
• Usage charge — for each 30-minute interval, the import kWh for that interval is priced at the rate that applies to that time of day and season. For a single-rate plan every interval uses the same rate. For a time-of-use plan, the rate varies by period (peak, off-peak, shoulder).
• Controlled load — if your meter has a controlled load channel (channel E2) and the plan publishes a controlled load rate, those intervals are priced at that rate. Many Victorian plans publish no controlled load rate at all. Those bill the circuit as ordinary usage, so we price it at the plan’s general rate and flag it on the card — a plan with its own controlled load rate is usually cheaper for that energy.
• Stepped and block tariffs — some plans charge different rates once usage crosses a daily or monthly threshold. Nemity tracks usage against the correct reset period for each plan: daily (the most common), monthly, or quarterly.
• Solar feed-in tariff — export intervals are credited at the plan’s feed-in rate. Where the feed-in rate varies by time of day, each export interval is credited at the rate for that period.
• Conditional discounts — many plans offer a percentage discount (e.g. “12% pay-on-time discount”). Nemity takes every one off the price. Where a discount depends on something we cannot check, such as paying on time, the price is marked with a * and its note gives the price without the discount.

Some plans offer electricity at zero cost (or a deeply discounted rate) during specific hours — typically overnight or midday. Nemity identifies these windows from the plan rates and applies them correctly to the relevant intervals in your data.

If you use your current plan’s free window heavily (by running an EV, hot water or the dryer in those hours), your interval data reflects that extra usage. Tell us about that window and the “usage reduction” slider can model how much of it you would simply do without, once the power stops being free. It is a separate control from “habit flexibility”, which moves load to a cheaper time rather than removing it.

A window that was merely cheaper is not treated the same way. Nothing about a 16c rate makes a household use more than it needs, so only a genuinely free window feeds the reduction — and it is skipped entirely on a new plan that gives you the same free hours, because there is nothing for you to give up.

Some retailers file a real benefit — a sign-up credit, a bonus feed-in rate — only as prose in their CDR marketing text, not in the structured rate data Nemity reads automatically. Nemity reads and prices as many of these as possible, but with thousands of plans on the market, it will not catch every one.

Where a derived figure comes from marketing text rather than structured data, it is marked with an asterisk so you know to check it directly with the retailer.

• Demand tariff plans — these charge based on your peak demand (the highest kW drawn at any point in a period), not just total kWh. Demand-tariff plans are left out. No Victorian distributor assigns a residential demand network tariff any more, so a household cannot be put on one — and priced against real household usage, none of them wins. Victorian Energy Compare may still list them.
• Benefits that cannot be turned into a dollar figure — loyalty points, cashback schemes, or rewards programmes. Nemity says so in the plan detail rather than guessing.

Sign-up credits are included. Where a plan offers one — as filed data, or written in the offer text when that is the only place it appears — Nemity prices it. You choose whether it counts: rank by ongoing cost, or by all-in cost that includes one-off sign-up bonuses.

Other comparison sites usually count a sign-up bonus no matter when it lands, so a bonus paid after six months still flatters the total. Nemity counts a credit only for the stretch you are comparing. A bonus paid after six months does not appear in a three-month comparison at all. A bonus paid monthly over a year contributes only the payments that fall inside the period you chose. Nothing is hidden: anything outside the period is shown beside the price.

Energy plans are complex. Tariff structures, conditional discounts, time-of-use windows, and seasonal rates all interact in ways that are difficult to model perfectly. Nemity works hard to be accurate, but the estimates are not a substitute for reading the plan terms or talking to a retailer before switching. Always verify a plan’s rates directly with the retailer.

If something looks wrong — a result that doesn’t match your actual bill — please let us know. Feedback like that is how the calculation gets better.