What a battery actually earns on a spot plan: a year of real Tasmanian numbers

Most articles about spot pricing and batteries are written by people selling one or the other, and they tend to quote the good months.

We have a full year of actual bills for a Tasmanian house on a wholesale plan, reconciled line by line against what the same energy flows would have cost on a standard Aurora tariff. This article reports what that showed, including the parts that don’t flatter the idea.

The headline that surprised us

Over the 2025-26 financial year, the house paid $1,601.79 on the wholesale plan. The identical energy flows on Aurora’s Tariff 93 would have cost $1,361.15.

The standard tariff was about $240 cheaper over the year.

That is the opposite of the result you would expect from anyone promoting spot pricing, and it’s worth sitting with before we explain it. A wholesale plan is not automatically cheaper. For much of that year, it wasn’t.

Why, and what changed it

Two things explain the gap.

Season. Tasmanian wholesale prices are strongly seasonal. Through the winter of 2025 the Tasmanian region averaged $118–125/MWh — well above the fixed off-peak rate on a standard tariff. Spot pricing lost badly in those months. In spring it reversed: September to December saw wholesale averages of $24–40/MWh, and a large share of the year’s negative-price hours. Any comparison run over a few weeks is measuring a season and nothing else.

Management. The months where the wholesale plan won are the months where the battery was being actively managed against prices. Looking at the same house month by month:

Month	Wholesale plan vs standard tariff
June 2026	$24.17 ahead
July 2026	$78.85 ahead
August 2026	$52.94 ahead

Across the 2026-27 financial year to date, the wholesale plan is $131.79 ahead. Same house, same retailer, opposite result — because the battery is now doing something with the price signal rather than just sitting on a market plan and hoping.

That’s the actual finding: the plan doesn’t save money. The plan plus something that responds to it saves money. A spot plan on its own is just exposure.

The number that matters more than either

Here is the part that gets buried in retailer comparisons, and it’s the most important number in this article.

In the same modelling, the no-battery baselines came out at roughly $3,132 and $3,211 depending on retailer. With a battery, both options landed near $2,400–2,500.

So:

Choosing between retailers moved the bill by roughly $90–240 a year.
Having a battery at all moved it by roughly $700 a year — on either retailer.

The battery is worth around six times more than the retailer choice. If you’re weighing up both decisions at once, that ratio should tell you which one to think about first. And unlike the retailer comparison, the battery’s value doesn’t depend on which way the wholesale market happened to move this season.

What good management actually looks like

The mechanism is less exciting than people expect. It isn’t clever trading. It’s the peak share.

Tracking what proportion of that house’s grid imports landed inside the expensive network peak window:

Month	Share of imports during peak
June 2026	24%
July 2026	6.4%
August 2026	2.21%

That progression is the whole strategy in three numbers. Buying almost nothing during the expensive hours is what produces the savings — not spotting a price spike, not trading, just not being in the market when it’s dear.

The August 2026 bill shows the effect cleanly against the year before. Same month, two years running:

August 2025: 810 kWh imported, $215.93 net — about 26.6 c/kWh
August 2026: 1,256 kWh imported, $214.00 net — about 17.0 c/kWh

The house used 55% more energy for the same money, because it bought that energy at better times. That comparison is from the issued bills, not a model.

What about selling into price spikes?

This is the part people find most exciting and it delivered the least.

Across an entire financial year, exporting into wholesale price spikes earned 67 kWh, worth $38.97. That is the total. It includes days when the market hit extraordinary prices — over $20,000/MWh on two occasions.

The reason it’s so small is structural. Spikes are brief, a home battery’s discharge rate is limited, and the system quite correctly prioritises covering the house before selling. By the time you’ve served your own load, there isn’t much left to sell, and the window has usually closed.

There’s a related finding worth stating because it’s counterintuitive: across that year, ordinary surplus solar earned more on a fixed feed-in tariff ($149) than on spot pricing ($84 plus $39 of spikes). Everyday exports happen in the middle of the day, which is precisely when wholesale prices are lowest because everyone else’s solar is exporting too.

So the advantage of a wholesale plan is on the buy side, not the sell side. Anyone pitching spot pricing primarily as a way to earn more from your exports has the mechanism backwards.

What about homes that aren’t on a wholesale plan?

We’ve run the same comparison for several Tasmanian homes still on standard tariffs, pricing their own actual consumption both ways over a matched period. Those comparisons showed the wholesale plan cheaper by roughly 5% to 10% on the energy component — somewhere between about $110 and $325 a year, depending on the household.

Two caveats we attach to those figures every time:

The window was spring, which is the season that favours wholesale pricing most. The full-year result above is the corrective.
They’re comparisons of the plan alone, before any battery management. What the battery adds on top is the larger and more reliable number.

So is it worth it?

An honest set of conclusions from a year of real bills:

A wholesale plan is not automatically cheaper. Over 2025-26 at this house it was about $240 dearer than a standard tariff.
Season dominates short comparisons. Winter favours fixed rates; spring favours wholesale. Judge it over a year.
Active management is what flips it. The managed months won; the unmanaged months lost.
The battery matters roughly six times more than the retailer. That’s the decision to get right first.
The savings come from the buy side — avoiding expensive hours — not from selling into spikes, which earned under $40 across a whole year.
On a fixed feed-in tariff, everyday exports are worth more, because your surplus arrives when wholesale prices are at their lowest.

None of this makes wholesale pricing a bad idea. It makes it a conditional one: worth it for a household that has storage and something managing it, questionable for a household that doesn’t.

The most useful thing you can do before any of this applies to you is pull out your last bill and find three numbers — your import rate, your feed-in rate, and your tariff. The gap between the first two is what a battery is worth to you on any plan at all, and it’s the number that stays true regardless of what the market does.

This guide was written by the Tasmanian solar team at Solar Generation Tasmania. Figures are from issued electricity bills and AEMO’s published Tasmanian region price data.

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Published by Solar Generation Tasmania. General information current as at publication — rebates, tariffs and prices change, so confirm current figures before deciding.