How much of the saving comes from changing your tariff?

Start with the imported electricity

The Tasmanian regulator’s 2026–27 standing offers list Tariff 32 at 24.75c/kWh plus $1.82/day. Tariff 93 lists 36.1878c/kWh peak, 17.02c/kWh off-peak and $1.723469/day, including GST. These are reference prices, not a claim that every household pays them. Check the regulator’s current prices and your actual offer.

For a solar home, use electricity bought from the grid, not total appliance consumption. Otherwise, the comparison charges you for electricity supplied by your own panels. Keep export credits in a separate calculation.

Same 20 kWh imported, different daily cost

These invented days each import 20 kWh. The time-of-use cases change only the proportion bought at the peak rate. Supply charges are included; export credits, concessions, discounts and other fees are excluded.

• Flat rate: 20 × $0.2475 + $1.82 = $6.77.
• 25% peak: 5 × $0.361878 + 15 × $0.1702 + $1.723469 = $6.09.
• 50% peak: 10 × $0.361878 + 10 × $0.1702 + $1.723469 = $7.04.
• 75% peak: 15 × $0.361878 + 5 × $0.1702 + $1.723469 = $8.00.

Results round to cents only at the end. No battery has been added in this example. The change in cost comes entirely from tariff and timing. Your imported volume and peak share will vary, so none of these days is an annual bill estimate.

Ask for a four-case comparison

1. Current equipment, current tariff: reproduce the recent bill before modelling changes.
2. Current equipment, proposed tariff: show what switching alone might achieve, subject to eligibility.
3. Proposed equipment, current tariff: isolate the effect of adding solar or storage where that tariff can be retained.
4. Proposed equipment, proposed tariff: show the combined result and any extra metering or installation costs.

All four cases need the same dates, weather assumptions and household demand. If a case is unavailable, label it unavailable and explain why. Do not quietly assume the old tariff remains an option.

Compare the combined case with both the current arrangement and the tariff-only case. The second comparison reveals how much extra benefit the equipment provides after an available plan change. It prevents a cheaper tariff from doing all the work in a battery sales calculation.

Give winter its own check

Ask for monthly imports, exports and battery discharge rather than only an annual saving. In your winter records, look for heating use during expensive periods and whether the proposed battery has enough energy available beforehand. Then ask where that charge comes from: spare solar or purchased electricity.

If the model buys energy to charge the battery, it must count that purchase and charging losses. A full battery icon is not evidence of a free charge. Compare the winter result with summer and shoulder months; do not scale a favourable week across the year.

Keep the interval file’s time zone and daylight-saving treatment with the analysis. Get the applicable peak schedule from your retailer before classifying the readings. An hour assigned to the wrong price can distort the apparent value of storage.

What to request next

Ask the installer for the four cases, monthly energy flows and the tariff schedule used. Once the charging opportunity is clear, use the battery size guide to examine capacity rather than choosing a size from the quarterly bill alone.

Prepare your project brief to check participating installer availability. Solvetted may receive a referral fee. The examples here are arithmetic illustrations, not measured household outcomes or a recommendation to switch plans.