Which hot water system you can have is an electrical question long before it is a plumbing one. Some draw more power on their own than the whole house is connected for, and that is worth knowing before the unit arrives on a truck.
Pricing agreed before we start. We usually reply the same day.
Hot water is the single largest energy use in most Australian homes, which is why the choice matters and why the marketing around it is so loud. What gets skipped is that each type makes a completely different demand on your electrical installation, and two of them can exceed what an ordinary house is connected for.
A storage system takes a modest element and runs it for hours, usually overnight or through the middle of the day, which is easy on the supply and cheap if it is on the right tariff. An instantaneous electric system does the opposite: it heats water only while you are using it, so it needs an enormous amount of power for a few minutes at a time. A heat pump sidesteps the problem entirely by moving heat rather than making it.
So the useful conversation happens before you choose, not after. We check what the existing circuit and the incoming supply can actually carry, tell you which options are genuinely available to your house, and what it would cost to make the others possible.
Then there is the tariff side, which is where most of the running cost is decided and where an electrician is the one who can actually change anything.
The same house, four different systems. The dashed line is roughly what a common single-phase connection gives you for the entire property, not just the hot water.
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What it means: a heat pump or a storage system fits comfortably inside an ordinary domestic supply. A whole-house instantaneous electric unit does not, which is why it usually arrives with a three-phase supply upgrade attached. None of that makes it a bad choice, but it should be priced in at the start rather than discovered on installation day.
This is where the running cost is actually decided, and it is the part of hot water that sits squarely with an electrician rather than a plumber.
A separately wired, separately metered circuit that your distributor switches on and off, in return for a cheaper rate. It is not a setting on your bill, it is physical wiring, which is why adding one is electrical work.
Around half a million Ausgrid customers have one. If your house does not, it can usually be added.
Ausgrid runs two. Controlled Load 1 suits larger systems of roughly 250 to 630 litres and guarantees at least 6 hours of supply in any 24 hours. Controlled Load 2 suits smaller systems of about 100 to 250 litres and gives at least 16 hours a day.
The tank has to be big enough to ride through the off periods, which is why the two are matched to size rather than offered as a free choice.
From July 2024 Ausgrid moved controlled load switching to take advantage of daytime solar rather than the traditional overnight window. Controlled Load 2 now includes a minimum of four hours between 7am and 5pm.
Plenty of systems are still set up around the old pattern, which is worth revisiting.
Heating water in the middle of the day on your own generation is close to the cheapest hot water available, and a storage tank is effectively a large, cheap battery for heat.
Getting the timing right is a wiring and control question, and it is often the single best return on a small amount of electrical work.
From an electrical point of view rather than a sales one.
| Type | Typical draw | Supply impact | Worth knowing |
|---|---|---|---|
| Electric storage | 3.6 kW element | Easy. Dedicated circuit, often controlled load | Cheap to run on the right tariff. The default in most Sydney homes |
| Heat pump | Around 1 kW | The easiest of the four | Needs outdoor space and airflow, and makes some noise. Pairs very well with solar |
| Instantaneous electric | 12 to 21 kW or more | Frequently needs a three-phase supply upgrade | No standing losses and no tank, but the connection cost can dominate the decision |
| Gas or solar with electric boost | Modest | Small, but still needs a circuit and isolation | The electrical work is minor, which does not mean it is optional |
Sizing is the other half of the decision and it is genuinely simple: too small and you run out mid-shower, too large and you pay to keep water hot that nobody uses. Controlled load makes that worse in both directions, because the tank has to carry you through the hours when the supply is off.
We would rather have that conversation with you before the unit is ordered than be asked to make an undersized system behave afterwards.
A useful distinction, because it decides who you should be calling.
No hot water at all, and nothing leaking
Often a failed element or thermostat, a tripped circuit, or a controlled load circuit that is not being switched on. If the tank is cold and dry, it is more likely ours than a plumber's.
Check whether the hot water breaker at the board has tripped before anything else.
It trips the safety switch
Usually a failing element letting current leak to earth through the water, which is exactly the fault an RCD exists to catch. Occasionally it is moisture in the wiring at the tank.
Repeatedly resetting it is not a fix, and on an element fault it will get worse rather than better.
You run out much earlier than you used to
On a two-element system one element may have failed, so the tank is only heating half its volume. It can also be a controlled load switching pattern that no longer matches how the household uses water.
Both are worth checking before concluding the tank is finished.
Water is hot at night, cold by evening
Classic controlled load symptom. The tank is heating during its allotted window and running out before the next one, either because the tank is undersized for the household or because the switching times no longer suit.
Since the times changed in 2024, this one has become noticeably more common.
Most hot water electrical work is ordinary licensed electrical work: the circuit, the isolation switch, the connection at the tank, and testing afterwards. That covers a straight replacement of an existing electric system.
Level 2 accreditation is needed once the job touches the network side, which is exactly what happens when a house needs more supply for an instantaneous unit, or when a controlled load is being added and the metering has to change. We hold it, so a supply upgrade does not become a second trade and a second wait.
Either way the work is certified. We lodge a Certificate of Compliance for Electrical Work within 7 days of testing, which since 1 July 2026 goes through the BCNSW eCert portal.
If you are replacing a system, the moment to involve us is when you are choosing it, not when it is sitting in the driveway.
A controlled load is a separately wired and separately metered circuit that your distributor switches on and off, in exchange for a cheaper rate. Ausgrid runs two: Controlled Load 1 suits large systems of roughly 250 to 630 litres and guarantees at least 6 hours of supply in any 24, while Controlled Load 2 suits smaller systems of about 100 to 250 litres and gives at least 16 hours a day. Around half a million Ausgrid customers are on one. If your tank is large enough to ride through the off periods it is usually worth having, and it needs its own circuit, which is where we come in.
Largely, yes. From July 2024 Ausgrid shifted controlled load switching times to make use of daytime solar generation rather than sticking to the traditional overnight window. Controlled Load 2 now includes a minimum of four hours between 7am and 5pm. If you have solar, heating water in the middle of the day using your own generation is usually the cheapest hot water you will ever get, and it is worth reviewing how your system is set up rather than assuming the old overnight pattern still applies.
Because it heats water on demand rather than storing it, so instead of a modest element running for hours it needs an enormous amount of power for the few minutes you are in the shower. A whole-house instantaneous electric unit commonly draws 21 kW or more and is usually three-phase, against 3.6 kW for a storage element. A common 63 amp single-phase supply is around 14.5 kW for the entire house, so the unit alone would exceed it. That is why this decision belongs with your electrician before you buy, not with the plumber on installation day.
For anything other than a like-for-like gas swap, usually yes. The plumbing side handles the water. The electrical side handles the circuit, the isolation, the controlled load wiring and metering if you are using one, and the question of whether the house can carry the load at all. On a straight replacement of an existing electric system it can be simple. On a changeover between types it rarely is.
From a supply point of view it is the easiest of the lot. A heat pump typically draws somewhere around 1 kW because it moves heat rather than generating it, so it rarely creates a capacity problem and it pairs extremely well with solar. The trade-offs are physical rather than electrical: it needs outdoor space with airflow, and it makes some noise, which matters if the only sensible position is under a bedroom window or against a neighbour's boundary.
Attending your job is a chargeable callout. We confirm what it costs when you book, and the price for the work itself is agreed before we start, so there are no surprises on the invoice.
Based in Castlecrag, covering all of Sydney. A few of the suburbs we work in most:
Covering all 48 North Shore suburbs. See the full list of locations we service.
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