A demand tariff adds a charge based on the highest average power, in kilowatts, that your property draws in any single half-hour during a defined peak window, usually assessed over a monthly billing period. It sits alongside the familiar charges for energy used (kWh) and the daily supply charge. The practical consequence is simple but surprising: one busy half-hour, such as air conditioning, the oven and an EV charger all running at once, can set that part of the bill for the entire month.

How the meter measures your demand

A smart or interval meter records how much energy crosses it in short, time-stamped intervals. For demand billing, the energy in each 30-minute interval is converted into an average power figure. Because a half-hour is half of one hour, the kilowatts equal the kilowatt-hours in that interval multiplied by two. The highest value inside the charging window becomes your demand for the period. How the meter records import and export in the first place is covered in smart meters and solar.

Averaging over the half-hour matters. A kettle drawing 2.4 kW for three minutes adds only 0.12 kWh, which lifts the half-hour average by just 0.24 kW. A 7 kW EV charger running for the whole interval adds 3.5 kWh and lifts demand by the full 7 kW. Sustained loads, not brief spikes, set demand charges.

The illustrative evening below shows how one interval can dominate.

If the 5:30 pm interval falls inside the demand window, the household is billed as if it needed 10.6 kW, even though it averaged under 4 kW for the rest of the evening. Starting the car a few hours later would have cut the billed demand to less than half.

Common features of demand tariffs

Structures vary between networks and retailers, so read your plan's details rather than assuming. Most share these features:

• A charging window. Only intervals inside a set window, often late afternoon and evening on working weekdays, count towards demand. A large load at 11 am or 10 pm may not count at all.
• A rate per kW. Demand is priced in dollars per kW, applied per day or per month to your highest reading.
• A reset period. Demand usually resets each billing month, so one bad day affects one month rather than the whole year.
• Seasonal differences. Some structures charge more for demand in summer and winter, when networks are under the most stress.
• Lower usage rates. Energy charges are often lower than on a flat or time-of-use plan, because part of the network cost has moved into the demand component.

There are also two layers to keep in mind. Networks charge retailers using network tariffs, which may include demand. Retailers then decide how to package that cost into the retail plan you see, so a demand-based network tariff does not always appear on your bill in the same form.

Residential and business demand charges compared

The kVA point matters for businesses. Where demand is measured in kVA, a poor power factor from motors and other inductive loads raises the billed figure even when the real power used is unchanged, which is why power-factor correction can reduce some business demand charges.

Managing a demand charge

Because the charge depends on a single interval, the goal is to stop large loads stacking up inside the window. Useful approaches include:

1. Stagger big appliances. Run the oven, dryer and dishwasher one after another rather than together during the window.
2. Move flexible loads out. Schedule EV charging, pool pumps and electric hot water for before or after the window. Many chargers let you set a start time or a lower current.
3. Pre-cool or pre-heat. Bring the house to temperature before the window starts, then let the air conditioner hold it at a moderate setting.
4. Configure a battery for demand, not only self-consumption. A battery set to cap grid import at a threshold during the window protects the demand figure. Its continuous discharge rating in kW sets how much it can shave, as explained in how battery storage technology works.
5. For businesses, automate. Demand management systems monitor site load and shed or delay non-essential equipment as a threshold approaches.

Will a demand tariff cost you more or less?

It depends on the shape of your load, not simply on how much energy you use. A household with steady evening use and flexible appliances can pay less, because lower usage rates outweigh a small demand charge. A household with unmanaged evening spikes can pay noticeably more. The reliable way to tell is to run twelve months of your own interval data through each option, comparing a demand plan with flat and time-of-use tariffs. Your retailer or distributor can usually provide that data on request.

Next steps

For businesses, a Demand-Charge Analysis in the Blue Energy Solar market identifies which half-hours set your charge and what load shifting, a battery or power-factor correction could change, from $690. Households can start with an Electricity Bill Audit at $99, which checks tariff type, usage pattern and feed-in rate. Both prices are indicative and confirmed after a site assessment. If a battery or solar upgrade looks worthwhile, request a free assessment from Blue Energy Solar.

Frequently asked questions

Will adding solar panels lower my demand charge?

Only if the demand window falls in daylight hours. Most residential windows run into the evening, when solar output is low or gone, so panels alone rarely reduce the billed figure. For businesses with daytime windows solar can help, but a single cloudy half-hour on a busy day may still set a high reading. Pairing solar with a battery or load control gives more dependable results.

Do demand charges apply on weekends and public holidays?

On many residential demand tariffs the window applies only on working weekdays, so weekend and public holiday intervals are ignored. Business tariffs vary more, and some measure demand at any time. Check your plan's tariff description or ask your retailer for the exact window, because running heavy loads on a weekend afternoon is one of the easiest ways to avoid a high reading.

Can I move off a demand tariff if it does not suit me?

Often, but not always. Network rules determine which network tariffs are available to your connection, and some customers are assigned a cost-reflective tariff when a smart meter is installed. Retailers may still offer plans that present those costs differently. Ask your retailer which options apply to you, and compare them using your own interval data rather than an average household estimate.