Energy cost calculator

Field use cases

Use this calculator when a load has a defined kW value and the project needs a transparent running-cost estimate. Typical Australian work situations include a workshop compressor, a retail lighting row, a pump or small plant load, a tenancy fit-out allowance, a temporary site load, or a maintenance note where the user needs to understand the cost impact of operating hours.

The result is most useful when it is tied to a specific load boundary. A "7.5 kW compressor" record is more useful than a generic "workshop load" record because the reviewer can check the schedule, the operating pattern and the tariff value later. A lighting row, pump duty estimate or equipment group should be named in the same way a load schedule names it.

This page does not estimate the full electricity bill. It only multiplies entered load, operating time, duty factor and entered energy tariff. That narrow boundary is deliberate. It keeps the arithmetic visible and prevents demand charges, time-of-use bands, fixed supply charges, retailer discounts, solar export credits and GST treatment from being hidden inside one number.

Tariff input checklist

The tariff field is a manual input. Treat it as a documented estimating value, not as a value discovered by the calculator. For small customers, the AER and Australian Government Energy Made Easy are useful public source categories for understanding retail plan context. For commercial, industrial or embedded-network work, the project may have a retailer contract, site-specific tariff schedule or internal estimating rate.

Keep the tariff basis with the result. Record whether the c/kWh value came from a current retailer plan, a previous bill, a comparison record, a client-provided assumption, an internal estimating rate or a project-specific schedule. If the tariff has peak, shoulder and off-peak bands, this simple calculator can still be used for one band at a time, but it does not model the split automatically.

What the result can decide

The primary result is an estimated energy cost for the entered period. The secondary results keep the daily energy, period energy, entered tariff and average daily cost visible. Those values are useful for quick comparisons: one lighting row against another, a longer operating period against a shorter one, or a high duty factor against a more realistic cycling assumption.

The result can support an estimating note, a maintenance discussion, an operating-cost comparison or a project record. It cannot decide whether the site is on the best retailer offer. It cannot interpret a bill. It does not include demand charges, time bands, fixed supply charges, solar export credits, controlled-load arrangements or network tariff details unless the user has already converted those into a simple entered c/kWh value for the specific comparison.

Review process flow

Start by defining the load. If the equipment is a motor, pump, compressor or fan, decide whether the entered kW is the electrical input load for the condition being estimated. Do not mix shaft output, rated motor size and measured input without recording the basis. If the kW value comes from a schedule, keep the schedule revision with the estimate.

Next define the operating period. A 30-day retail lighting estimate, a 22-working-day workshop estimate and a 14-day pump duty estimate are different questions. The calculator does not know the business hours, production pattern, occupancy schedule or control logic. Those assumptions belong in the hours, days and duty factor fields.

Then enter the tariff. If the site has a flat energy rate, enter that rate directly. If the site has time-of-use pricing, run separate estimates for the relevant bands or keep this page as a single-band approximation. If the site has demand charges or fixed supply charges, record those outside this calculator.

Worked Australian examples

A workshop compressor is entered at 7.5 kW. It is expected to operate for 6 hours per working day across 22 days, but the compressor is not loaded continuously, so the duty factor is entered as 0.65. With an entered energy rate of 32 c/kWh, the daily energy is 29.25 kWh/day and the period energy is 643.50 kWh. The estimated energy cost is $205.92 for the entered period, or $9.36 per day on average.

The useful part of this example is not only the dollar figure. The duty factor is visible, so a reviewer can challenge it. If the compressor is short-cycling, leaking air or running after hours, the estimate can be rerun with different hours or duty factor. If the tariff came from a general assumption rather than a site-specific record, the result should be treated as an estimating line rather than a bill comparison.

A retail lighting row totals 2.4 kW and is reviewed across 10 hours per day for 30 days with duty factor 1.0. At 28.5 c/kWh, the period energy is 720.00 kWh and the energy-only cost is $205.20. This is useful when comparing lighting schedules or control assumptions, but it does not assess lighting quality, emergency lighting, controls commissioning or tenant billing.

A small pump estimate uses 5.5 kW for 24 hours per day across 14 days with duty factor 0.45 and an entered rate of 34 c/kWh. The long-hours warning is intentional: it asks the reviewer to confirm whether the duty factor is a real operating assumption or just an optimistic allowance. For pumps, compressor loads and process equipment, that distinction often matters more than the last decimal place in the cost result.

Scenario matrix

Energy-cost estimates are often used as quick comparisons. Change one assumption at a time so the comparison remains clear. If the tariff changes at the same time as the operating hours and duty factor, the user may not know which assumption drove the difference.

Related tools

Use the load current calculator when the entered kW needs to become current for a cable, switchboard or protection review. Use the kVA, kW and power factor calculator when the available project value is kVA and power factor rather than kW. Use the cable cost and quantity calculator when the question is material estimating instead of running energy. Use the power factor correction calculator when the cost discussion is connected to a documented power-factor issue.

FAQ

The page FAQ is limited to the energy-cost worksheet boundary: where the tariff input should come from, why duty factor is separate, what the calculator excludes and what should be checked after the result. Questions about retailer comparison, bill interpretation, demand charges or time-of-use modelling belong outside this simple kWh cost calculation.

Stop points

Stop before relying on the result if the load value is not an electrical input kW value, if the duty factor was guessed without any operating basis, or if the tariff value is not tied to the relevant site, retailer, plan or project assumption. Stop if the energy rate is only one part of a more complex billing structure and the decision depends on the full bill.

For Australian project records, keep the entered values with the estimate: load reference, kW, hours per day, days, duty factor, tariff source and date or revision where available. The export is a calculation record for discussion. It is not a retailer comparison, a bill interpretation or a promise that changing one load will produce the same dollar movement on a real bill.