Australia's Wholesale Electricity Prices: Saving on the Spot Market
Most Australian households pay a flat rate or a simple time-of-use split. But a growing number are on wholesale-linked plans, where your price follows the spot price in the National Electricity Market (NEM) — the market that sets the wholesale cost of power across the eastern states. Those prices swing harder than almost anything else in the world: often negative in the sunny middle of the day, and steep on hot evenings. That’s a big opportunity, and it’s nearly impossible to chase by hand. This guide explains how it works and how to capture it automatically.
How wholesale-linked pricing works
The NEM covers five regions — New South Wales, Queensland, South Australia, Tasmania, and Victoria — and each has its own spot price that updates continuously through the day. On a wholesale-linked retail plan, your bill tracks that spot price for your region, plus the fixed network charges, your retailer’s margin, and GST.
Two things make this different from a flat or time-of-use plan:
- The price moves all day, and the swings are huge. Rooftop solar is so abundant across Australia that the middle of the day is frequently the cheapest time to use power — sometimes with negative wholesale prices, where you’re effectively paid to consume. Then, as the sun sets and solar drops off, evening prices can spike hard.
- It’s regional. A hot afternoon in South Australia and a mild one in Tasmania produce very different prices, so your region’s curve is its own.
That “solar sponge” in the middle of the day, paired with a steep evening ramp, is the shape automation is built to exploit.
Where the savings are
Because the cheapest hours shift day to day — and often sit in the middle of the day rather than overnight — the wins come from reacting to each day’s price curve:
- EV charging during the cheap (or negative-priced) solar hours around midday, or the overnight trough, instead of the evening ramp.
- Pre-cooling or pre-heating ahead of the evening spike, so your air-conditioning coasts through the most expensive hours.
- Water heating and battery charging timed to soak up the cheap midday solar and avoid the peak — the classic “solar sponge” move.
On a flat plan, none of this matters; you pay the same either way. On a wholesale-linked plan, when you use power is most of the bill.
How to capture it: by hand vs. automatically
By hand, you’d watch your region’s spot price and forecast through the day and manually kick off the EV charger, air-conditioner, and hot water when prices dip — while dodging the evening spike. Nobody realistically does that around the clock, and the negative-price windows are often short.
Automatically is the whole point of a plan like this. Hungry Machines pulls the forward price forecast for your NEM region, combines it with tomorrow’s weather plus a custom model of your home, then builds an optimised schedule. It charges the EV and heats water during the cheap solar sponge, pre-cools just enough to skate past the evening spike, and keeps big loads out of the peak. Because the plan is rebuilt against the latest forecast, it catches the deep midday troughs — including negative prices — that a fixed timer sails right past.
Common questions
Is a wholesale-linked plan risky?
Your rate follows the National Electricity Market, so a spike costs more in that interval. The NEM’s market price cap is high — into the thousands of dollars per MWh — so retailers offering wholesale pass-through typically apply their own caps, and it is worth reading exactly what yours is before signing up.
The exposure concentrates narrowly: a handful of hot summer evenings when demand peaks and generation is tight. In exchange you pay genuine wholesale cost the rest of the year, including the many midday intervals where abundant rooftop solar pushes prices to zero or below.
The honest version is that these plans reward flexibility and punish its absence. If you cannot shift load away from a 6 p.m. summer spike, a fixed or time-of-use plan is the safer choice.
Why are prices sometimes negative?
Because Australia has more rooftop solar per person than anywhere else, and on a mild sunny day it generates more than the grid needs. Large thermal generators cannot switch off and on cheaply, so at times they would rather pay to keep running than shut down and restart — which pushes the spot price below zero.
Negative pricing is now routine in the middle of the day across most NEM regions, particularly in spring and autumn when solar output is high and neither heating nor cooling demand is.
For a household on a wholesale-linked plan this is a genuine opportunity rather than a curiosity: it is the one time you are paid to consume. Running the dishwasher, charging the car or heating water at midday turns a grid problem into a credit on your bill.
Do I need solar or a battery to benefit?
No, though both raise the ceiling. The savings on a wholesale-linked plan come from when you draw from the grid, and the midday trough is available to every customer whether or not there are panels on the roof.
In fact the negative-price hours are arguably more useful to a household without solar, since a solar home is already self-supplying at exactly those times and has less grid draw left to shift. A battery helps most of all, because it can buy at negative prices and discharge into the evening spike.
The real determinant is how much of your consumption is time-flexible. Air conditioning, pool pumps, hot water and EV charging are all movable; lighting and refrigeration are not. A home with several of the former captures most of the opportunity with no new hardware.
Next steps
Australia’s spot market is the wholesale cousin of the hourly markets elsewhere — see how the same idea plays out in ComEd’s hourly pricing in the US and Octopus Agile in the UK. For the wider picture, start with our guide to time-of-use electricity rates. For the software side of it, see our guide to home energy management systems.
To let your home react to the spot market automatically, see how Hungry Machines works and sign up now.