Most solar homes send a good amount of energy back to the grid at midday. They are paid very little for it. At the same time, heating water is one of the largest single costs in a household. This reveals an obvious opportunity: instead of exporting surplus solar for a few cents, use it to heat the water the home needs anyway. That is exactly what a solar hot water diverter does.
This guide explains what a solar hot water diverter is. It covers how it works. It looks at why it suits Perth conditions so well. It compares it with the two main alternatives: a simple timer and a heat pump.
The Problem: Low-cost Exports, Expensive Hot Water
Feed-in tariffs in Western Australia are modest. They are particularly low in the middle of the day when most solar surplus occurs. The energy a home exports at that time is worth very little. Meanwhile, an electric hot water system is one of the biggest loads in the house. If it heats overnight or on grid power, it is quietly adding to the bill.
The mismatch is the point. A home is giving away low-cost energy during the day. Then it pays to heat water at another time. A diverter closes that gap. It moves the water heating into the sunny hours. It powers it with energy that would otherwise have been exported for almost nothing.
What a Solar Hot Water Diverter Is
A solar hot water diverter is a small electronic device installed in the switchboard. It watches the flow of energy at the meter. When it detects that the home is exporting surplus solar to the grid, it redirects that surplus into the electric element of the hot water tank instead. The water is heated with your own solar energy that would otherwise have left the property.
The clever part is that a diverter uses only the genuine surplus. It continuously measures how much energy is heading out to the grid. It matches the power sent to the hot water element to that amount. It ramps up and down as clouds pass or as the household’s own usage changes. It is not an all-or-nothing switch. It modulates smoothly so the home always uses its own solar first. It heats water with whatever is left over.
How It Works, in Practical Terms
The sequence is simple once the device is in place.
- The diverter senses surplus solar being exported, using a current sensor at the switchboard.
- It diverts an equivalent amount of power to the hot water element. It adjusts continuously so it only ever uses the excess.
- As the household’s usage rises or the sun fades, it eases back. It always leaves the home’s own needs met first.
- If the water has not reached temperature by the end of the day, most diverters can top it up. This happens either from the grid in the lowest-cost tariff window or on a scheduled boost. So the home never runs out of hot water.
Well-known options in Australia include standalone diverters such as the Catch Power unit. For homes with a Fronius system, the Fronius Ohmpilot performs the same job as part of the Fronius ecosystem. The right choice depends on the existing system and hot water setup.
Why It Suits Perth
A diverter makes particular sense in Perth. The city has strong, reliable midday sun. It has a large number of homes with electric storage hot water tanks. It faces the same low feed-in and export-limit pressures that reward using energy at home rather than sending it out. A diverter turns a daily surplus that was worth almost nothing into one of the most useful things a household can do with it: a tank of hot water heated by your own solar.
It also fits the broader direction of solar in Western Australia. As feed-in rates stay low and more systems are export limited, the value has shifted firmly towards self-consumption. Hot water is one of the easiest and largest loads to move into the sunny part of the day.
Diverter, Timer or Heat Pump?
A diverter is one of three common ways to heat water more at low cost with solar in mind. Each suits a different situation.
| Approach | How it heats the water | Best suited to |
|---|---|---|
| Solar diverter | Uses only surplus solar that would otherwise be exported | Homes with an existing electric-element storage tank and good daytime surplus |
| Timer or scheduler | Runs the element during the lowest-cost, sunniest hours, drawing some grid power | A simple, low-cost option where a diverter is not fitted |
| Heat pump | Uses a small amount of electricity to move heat, very efficiently | New systems or replacements, especially a home going all-electric |
These are not mutually exclusive. A diverter and a timer can work together. A household replacing an old system entirely may find a heat pump the better long-term answer. The choice comes down to what is already installed and what the household is trying to achieve.
Is a Diverter Right for Your Home?
A solar hot water diverter is an excellent fit for a specific and very common situation. A home already has solar and an electric-element storage hot water tank. It generates more solar during the day than it uses. In that case, a diverter is a modest addition. It quietly turns wasted export into hot water for years.
It is less relevant for homes with instantaneous gas hot water. It is less relevant for households that are replacing their hot water system altogether. In those cases, a heat pump may deliver more over the long run. As always, the sensible path is to match the solution to the existing system and the household’s plans.
How Positive Energy Solutions Can Help
Positive Energy Solutions designs solar systems around how a household actually uses energy. Heating water with surplus solar is one of the simplest, highest-value tactics available. The team can advise whether a diverter suits an existing hot water system. They can tell you whether a timer or a heat pump is the better route. They install the right solution as part of a considered system design.
Every installation is completed by our accredited installers and signed off to Positive Energy’s completion standards. It is backed by a 10-year installation workmanship warranty. Positive Energy Protection, powered by Omnidian, monitors the whole system for performance from day one.
Frequently Asked Questions
What is a solar hot water diverter?
It is a device fitted in the switchboard that detects surplus solar being exported to the grid. It redirects it to the electric element of the hot water tank. The water is heated with energy that would otherwise have been exported for very little.
Does a diverter use grid power?
By design, it uses only surplus solar. So it does not draw from the grid to heat water. Most diverters can, however, be set to top up the tank from the grid in the lowest-cost tariff window if the day’s solar was not enough. So the home never runs out of hot water.
Will a diverter work with my hot water system?
A diverter suits an electric-element storage hot water tank. It is not used with instantaneous gas systems. Whether it fits a particular home is confirmed by looking at the existing hot water system and solar setup.
Is a diverter better than a heat pump?
They solve the problem differently. A diverter makes excellent use of an existing electric tank at low cost. A heat pump is a more efficient system in its own right. It is often the better choice when replacing a hot water system entirely. The right answer depends on what is already installed.
Does a diverter work alongside a battery?
It can. A home with a battery usually charges the battery from surplus solar first. A diverter then makes use of any excess beyond that. The two can be configured to complement each other. So surplus solar is used as effectively as possible.
Turn Your Surplus Into Hot Water
For a Perth home with solar and an electric hot water tank, a diverter is one of the quiet wins of a well-designed system. It takes energy that was worth almost nothing as an export. It turns it into a genuine household saving, day after day.
Talk to the local team about heating your water with surplus solar: request your quote from Positive Energy
About the Author
Jason Wiktorowicz
Sales Manager, Positive Energy Solutions | Perth, WA
Jason has been at the centre of Western Australia’s energy transition for over a decade. He was Orchestration Lead on Project Symphony. That was WA’s largest virtual power plant pilot. He was Stream Lead on Project Encore. He worked directly with AEMO, Western Power and Energy Policy WA. He shaped how distributed energy resources connect and operate on the SWIS. That work included developing and rolling out CSIP-AUS. It is now mandatory for all new WA grid connections. He also led Emergency Solar Management. It was the first program of its kind in WA. He led VPP for Schools, which provided direct market benefits through Supplementary Reserve Capacity. He led REBAR, the WA Residential Battery Rebate scheme.
His earlier career spanned Synergy, Infinite Energy and Curtin University’s Sustainability Policy Institute. He co-authored peer-reviewed research on net-zero urban precincts, solar integration and peer-to-peer energy trading. It was published in the journal Urban Planning in 2018.
At Positive Energy Solutions, Jason leads sales with a focus on system design accuracy and long-term performance. Positive Energy Solutions installs solar and battery systems, EV chargers and heat pumps. It holds partner accreditations with Fronius, SigEnergy, iStore and SunPower.
10-year installation workmanship warranty. Positive Energy Protection, powered by Omnidian, performance monitoring included on all systems.
