Batteries for business: the demand charge, the weekday 5pm to 8pm window and the 100 kWh rebate line

What a demand charge is, and why the bill total hides it

Most people understand an energy charge: so many cents for every kilowatt hour used. A demand charge is a different animal. It is priced per kVA per month, and the kVA figure is the single highest 30 minute demand the meter recorded inside a set window during that month. One busy half hour sets the number. Every quieter half hour that month does nothing to bring it down.

It is a network charge. Energex sets it as the distributor and your retailer passes it on, so on a bill that breaks out the network components it sits with the network (NUOS, network use of system) charges rather than with the energy rates. If your bill does not show those lines separately, ask your retailer which network tariff you are on and for the demand charges itemised. Either way, the total at the bottom will not tell you how much of it came from one half hour on one evening.

Because it is measured over half hour intervals, it is sustained load that counts. A motor start lasting a few seconds barely moves a half hour figure. Several large loads running together for half an hour is what sets the peak.

Tariff 7200 in 2026/27: the windows and the rates

Energex's default network tariff for a business with a smart meter using 100 MWh or more a year is Large Time of Use Demand and Energy, tariff 7200 (written NTC7200 in Energex's documents). It has three demand windows, set out in Energex's Tariff Structure Statement for 2025 to 2030, and the 2026/27 prices come from the pricing proposal the Australian Energy Regulator approved on 22 April 2026:

Peak demand: weekdays, 5pm to 8pm. There is no peak window on weekends. The 2026/27 network price is $13.913 per kVA per month, excluding GST.

Off peak demand: 11am to 1pm, every day. The 2026/27 off peak demand price is zero.

Shoulder demand: everything else. Weekdays from midnight to 11am, 1pm to 5pm and 8pm to midnight, and weekends outside 11am to 1pm. The 2026/27 network price is $3.672 per kVA per month, excluding GST.

Two details catch people out. Energex counts a public holiday that falls on a weekday as a weekday, so a public holiday evening still sits inside the peak window. And these prices are new: Energex's network prices changed on 1 July 2026, and Energex's own pricing overview put the typical network bill on this tariff up by around 12 per cent.

Those are network prices. Your retailer may pass them straight through or package them differently in its contract, so the rates printed on your bill are the ones to use for your site. Smaller business sites can be on a demand tariff too, since Energex also has a small business time of use demand tariff. The tariff code on your bill is what tells you which one applies.

Why solar on its own cannot touch the peak demand charge

Put the peak window next to a solar generation curve and the problem is obvious. Between 5pm and 8pm the sun is low or already down. A rooftop array, however large, produces little or nothing at the moment the peak demand charge is being set.

Solar is still valuable on a commercial site. It cuts the energy you buy through the day and can pull down daytime shoulder demand. But the peak demand line is set in the evening, and only two things reach it: stored energy discharged into the window, or load moved out of it.

That is why, on a demand tariff, the battery can be the component carrying the numbers rather than the optional extra. It is also why the honest answer is not always a battery. A site whose load is almost all daytime, and which already runs light between 5pm and 8pm on weekdays, may have very little peak demand to take off, and solar on its own may be the right design. The interval data tells you which kind of site you are.

The arithmetic, and the one half hour that undoes it

The form of the sum is simple. Each kVA taken off the monthly peak is worth the peak demand rate for that month. Take the peak down by a number of kVA and hold it there, and the peak demand line falls by that number multiplied by the rate, month after month.

The catch is in the word hold. One missed half hour sets the charge for the whole month. If the battery runs out at half past seven on one busy weekday evening, the meter records that half hour, and the month is billed on it, no matter how well the battery held the peak on every other evening.

So a sound design does three things. It reserves battery charge for the window instead of letting the battery spend itself earlier in the day. It sizes the stored energy for the longest, heaviest weekday evening in the data, not the average one. And it works from a prudent estimate of the kVA reduction rather than the best case, because a best case that fails once in a month is worth nothing for that month.

There is a second trap, on the charging side. Shoulder demand is charged too, so a battery that refills hard from the grid in the afternoon or overnight can set a new shoulder peak and hand back part of what the evening discharge achieved. In 2026/27 the off peak demand price for 11am to 1pm is zero, which is one reason the charging plan matters as much as the capacity. Energy used in that window is still charged; it simply does not set a demand charge.

A worked example, in round numbers and purely illustrative: if a site's weekday evening peak is 100 kVA and a battery can reliably hold it to 80 kVA, the target is 20 kVA off the peak demand line every month, with enough stored energy to cover the full 5pm to 8pm window on the heaviest evening in the data. Whether that is worth doing is then a sum you can check yourself against the rate on your own bill.

The federal battery discount for business, and the 100 kWh line

The Cheaper Home Batteries Program is not only for homes. The Department of Climate Change, Energy, the Environment and Water says it supports batteries for residential and nonresidential premises, and that businesses can get the discount. For a commercial site, these are the rules that matter:

The ceiling is 100 kWh nominal. An eligible battery system must be between 5 kWh and 100 kWh of nominal capacity. A system above 100 kWh nominal is not partly eligible; it is not eligible at all.

Only the first 50 kWh of usable capacity earns certificates. A system between 50 and 100 kWh can still get the discount, but only on its first 50 kWh usable, and the rate tapers within that: the full factor up to 14 kWh, 60 per cent from 14 to 28 kWh, and 15 per cent from 28 to 50 kWh.

It needs solar, and it steps down. A battery that only stores energy from the grid is not eligible, and the installer must be accredited by Solar Accreditation Australia. The discount is set by the installation date, and it steps down on 1 January 2027 and every six months after that. Support is for one battery system per premises, the first time.

Check the solar size. DCCEEW's eligibility page lists solar PV systems of less than 100 kW among the conditions for the battery discount. If your site has, or is about to get, a larger array, confirm how the battery will be treated before counting on the discount.

Here is the lesson, and it runs the opposite way to most home advice. Size a commercial battery for the demand charge, not for the rebate. The discount is paid once, counts only the first 50 kWh usable and tapers hard above 14 kWh. The demand charge comes back every month. If the interval data says the evening peak needs more than 100 kWh nominal to hold reliably, shrinking the battery to stay under the line can cost far more over the life of the system than the one off discount was ever worth. If the data says the site does not need that much, staying under the line is a bonus. Either way, the load decides.

The certificate structure is explained in more detail in the federal battery rebate explained.

Commercial solar: the move to 1 MW is now law

The solar side has changed too. The Small scale Renewable Energy Scheme now covers solar systems above 100 kW and up to 1 MW, so they create small scale technology certificates instead of falling into the large scale scheme. The regulations are in place and apply to eligible systems installed from 1 October 2026, and the Clean Energy Regulator expects applications for these systems to open in mid to late November 2026. These mid scale systems get a fixed five year deeming period, and the Regulator's guidance on existing systems and extensions is still to come.

On a demand tariff site the two pieces fit together. A bigger array covers more of the daytime load and more of the energy a battery needs, and the battery covers the evening window the array cannot reach. The solar side is on our commercial solar page, and one of the commercial battery ranges we install is on our Kstar BluePulse commercial battery page.

How to check your own bill

You do not need anyone's software to find out whether this matters for your site. Take a recent bill, ideally for a busy month, and look for four things.

One: the network tariff code. Look for 7200 or NTC7200, or another tariff with Demand in its name. If the bill does not show it, ask your retailer.

Two: the demand lines. On a demand tariff you should see a peak demand charge and a shoulder demand charge, each with a kVA (or kW) figure and a rate per kVA per month.

Three: the kVA figure against the rate. Multiply the peak kVA by the peak rate and you have that month's peak demand charge on its own. Set it against the bill total. That share is the first sign of whether storage deserves a proper look.

Four: twelve months of interval data. Ask your retailer for the last 12 months of half hourly interval data in NEM12 format, the Australian Energy Market Operator's standard file format for interval metering data. It shows every half hour, so it shows which evenings set each month's peak, how long those peaks last and how much stored energy it would take to cover them. It is the most useful thing you can bring to a commercial battery conversation.

What a commercial battery proposal should be built from

When you ask for a proposal, this is the list it should be able to show its working on. If it cannot, it is a guess with a price on it.

Your interval data. Twelve months, half hour by half hour, not a monthly average and not an estimate from the roof size.

Your tariff windows and rates. The tariff actually on your bill, with its peak, shoulder and off peak windows applied to your own data, including how the battery recharges without setting a new shoulder peak. Energex also offers a storage tariff for large customers and is running a dynamic business tariff trial in 2026/27, so which tariff suits the site once a battery is installed belongs in the same conversation.

The kVA reduction it targets. A stated number, in the unit you are billed in, and how often the historical data says that target would have been missed.

Reserved state of charge. How much of the battery is held back for the 5pm to 8pm window, and what the system does on a heavy day when the site wants more.

The connection. On a three phase site the inverter capacity has to suit the supply and the switchboard, and larger systems follow a different Energex process. Energex treats systems over 30 kVA as larger systems: the application starts with an enquiry through its Electrical Partners Portal, Energex checks whether the local network can support the proposed system, and the connection is made under a connection contract, either as a basic connection on standard terms or as a negotiated connection. That takes time, and it belongs in the plan from the start.

The switchboard. Space, protection and metering for the new equipment, scoped up front rather than found halfway through. Our switchboard upgrades page covers that side of the work.

The discount, last. Whether the design lands under or over 100 kWh nominal should fall out of everything above, and the proposal should say which it is and why. For the wider checklist, see reading a battery quote.

Getting your site looked at

If your site is on a demand tariff, the useful first step is not a brochure, it is the data. Send us a recent bill and 12 months of interval data through our commercial solar page or commercial electrical page, and I will look at what is setting your peak before anyone talks about equipment. Anything that has to be measured on site is done at a design visit if one is needed, and our $299 design visit is credited back in full off the installation if you go ahead within 30 days of the visit.

The equipment comes after the numbers, and it is chosen for the site, not from a price list. If storage is not what moves your bill, I will tell you that too, along with what would.

Common questions