Your home can only draw so much power at any moment, and that ceiling is set by the chain of equipment connecting it to the street: the service line, the service fuse, the consumer mains cable and the main switchboard. For decades most homes stayed well within that limit because gas handled cooking, heating and hot water. As households add EV chargers, induction cooktops and reverse-cycle air conditioning, the important question shifts from how much energy the home uses in a day to how much power it draws at its busiest moment. That peak, called maximum demand, is what the supply must be able to carry.

The path from the street to your switchboard

Electricity reaches a typical house through a sequence of parts, each with its own rating:

1. The network: poles and overhead wires, or underground cables and pillars, operated by the local distribution network.
2. The service line: the overhead or underground cable that connects the property to the network.
3. The service fuse: a protective device, often in the meter box, that disconnects the whole supply if current exceeds its rating.
4. The consumer mains: the cable from the point of supply, such as the connection point on the house or the pit at the boundary, to the main switchboard.
5. The meter and main switchboard: the meter records energy flows, and the switchboard distributes power to individual circuits through breakers and safety switches.

The smallest rating in that chain sets the practical limit. A generous service fuse cannot help if the consumer mains are undersized, and heavy consumer mains do not help if the service fuse is small. How modern meters record two-way flows is explained in smart meters and solar.

Amps, volts and what a fuse rating means

Power equals voltage multiplied by current. Australian homes are supplied at a nominal 230 volts per phase, so each amp of current carries roughly 230 watts. As an illustration, a single-phase supply protected by a 63 A service fuse could carry about 14.5 kW before reaching the fuse rating (63 A multiplied by 230 V). Older homes may have lower-rated fuses or consumer mains sized for the loads of their era, while some supplies have higher ratings or three phases.

Three-phase supply delivers three separate 230 V phases, roughly tripling the available capacity when loads are spread evenly across them. The catch is that each phase has its own limit, so a large single-phase appliance still draws from one phase only.

Maximum demand: the busiest moment matters

Maximum demand is the highest combined load a home is expected to draw at the same time. It is not the sum of every appliance's nameplate rating, because people rarely run everything at once and many appliances cycle on and off. Electricians calculate it using the methods in the Wiring Rules, AS/NZS 3000, which allow for this diversity, or measure it by logging actual demand over time.

The table shows typical electrical loads and the current each draws at 230 V. Figures are approximate, and actual ratings vary by model and settings.

Add the upper figures together and the total exceeds 120 A, far beyond the illustrative single-phase supply above. In daily life these loads will not all run at full power together, but a winter evening with the car charging, heating running and dinner cooking can come surprisingly close to the limit. That is the scenario designers check.

What happens when demand exceeds capacity

A service fuse protects the service line and consumer mains from overheating. If demand stays above its rating for long enough, it operates and the whole property loses power while neighbours stay on. Before that point, heavily loaded cables run warmer and voltage drops further, especially where long consumer mains run down a driveway to a rear house. Signs worth reporting to a licensed electrician include:

• the entire property losing power while the rest of the street remains supplied
• lights dimming noticeably when large appliances start
• the main switch or several breakers tripping during busy periods
• discolouration or a burning smell at the meter box, which calls for keeping clear and treating it as urgent

Ways to live within the limit, or raise it

An upgrade is not always the first answer. Smart EV chargers can measure household demand with current sensors and slow charging when the home is busy. Hot water, pool pumps and EV charging can be scheduled at different times rather than stacking up in the evening. Efficient appliances help too, since a heat pump draws far less power than a resistive element for the same hot water. How these devices can be coordinated is covered in the smart home energy ecosystem.

When the numbers still do not fit, the options include a larger service fuse where the network permits, new consumer mains with a larger cable, a switchboard upgrade, or conversion from single-phase to three-phase supply. Network approval is usually required, and in NSW work on the service line and service fuse is carried out by an Accredited Service Provider (Level 2) electrician. None of this is owner work: meter boxes and mains cables stay live even with the main switch off.

Next steps

Before planning several new electric appliances, have the supply capacity and switchboard checked so any upgrades can be done once rather than piecemeal. The energy market lists an Induction & Electrification Assessment at $199, a Consumer Mains Upgrade from $2,490 and a Single-Phase to Three-Phase Upgrade from $3,490; these prices are indicative and confirmed after a site assessment. If you are also considering solar or a battery as part of the change, request a free assessment from Blue Energy Solar.

Frequently asked questions

Does a home battery increase the power my house can draw?

Partly, and only while it has charge. A battery supplying the home in the evening reduces the current drawn through the service fuse, up to the inverter's power rating. Once the battery is empty, or if a load exceeds what it can deliver, the grid supplies the rest. Designers therefore do not normally treat a battery as a substitute for adequate supply capacity.

Can solar panels overload the consumer mains?

In a typical home this is unlikely, because networks limit how much an inverter can export on each phase and designers check that the cable can carry that current. Long consumer mains can matter for a different reason: exported current raises the voltage at the house, which may cause the inverter to reduce output or disconnect. Cable size and length are assessed during system design.

Do I need three-phase power to go all-electric?

Not necessarily. Many all-electric homes run well on single-phase supply with sensible scheduling and a load-managed EV charger. Three-phase becomes more attractive for large homes with high heating and cooling loads, faster 11 kW home EV charging, or bigger solar systems where networks allow larger inverters across three phases. The decision depends on calculated maximum demand and the upgrade cost at the property.