Solar diverters for hot water in Perth: making the most of excess midday solar
A solar diverter detects surplus solar generation and redirects it to your electric hot water element instead of exporting at 2c/kWh under DEBS. For a typical Perth home on the A1 tariff, that's roughly $300-500 a year, with payback in about 12 to 17 months on a single-phase install.
A solar diverter is a small switchboard device that watches your solar generation and household consumption in real time. When it detects surplus solar, it redirects that surplus to your electric hot water element instead of letting it export to the grid under Perth's Distributed Energy Buyback Scheme (DEBS), which pays just 2c/kWh (some households still on the legacy REBS scheme get up to 7.135c/kWh instead). Either way, that's a lot less than the 33.26c/kWh you're paying to heat water with grid electricity.
For a typical Perth home with a 6.6kW solar system and a resistive electric hot water system on the A1 tariff, that swap is worth roughly $300-500 a year, and the diverter pays for itself in about 12-15 months. The saving is smaller on Midday Saver, where the cheap 9am-3pm window already narrows the gap between what you'd pay and what you'd otherwise export, but it's still a worthwhile upgrade. The rest of this guide covers how diverters work, what's on the market in Perth, and how to work out the saving for your own system.
How does a solar diverter work?
A solar diverter installs at your switchboard alongside your hot water element and continuously monitors your grid connection point:
- If solar generation exceeds household consumption, the surplus is about to be exported.
- The diverter detects that surplus and throttles power to the hot water element to match it.
- As household loads change (a kettle switches on, say), the diverter adjusts element power in real time so you're always using surplus, never importing extra grid power.
How this differs from a timer. A timer switches the element on at a fixed time regardless of the weather: if it's cloudy at noon, you import from the grid to heat water anyway. A diverter only activates when there's genuine surplus, so it never adds to your import.
Which solar diverters can you buy in Perth?
Catch Power (Green)
Australian-made and the most established option in the Perth market.
- Works with any resistive element
- Continuous monitoring via a current transformer on the grid connection
- Pairs with Catch Power's own app for monitoring
- Installed cost: approximately $450-650 on a single-phase supply, or $850-900 on three-phase, where each phase needs its own current monitoring and the switchboard work is more involved
MyEnergi Eddi diverter
UK-designed, sold in Australia, with a wider feature set for households already invested in the MyEnergi ecosystem.
- Supports two hot water zones (can also divert to a second element or a towel rail)
- Integrates with the Zappi EV charger on the same platform
- Installed cost: approximately $600-900
Solar Analytics + hot water control
Some solar monitoring platforms, Solar Analytics among them, can control a hot water element through a relay. It's less precise than a purpose-built diverter, but it reuses monitoring hardware you may already have.
CATCH Control (formerly Relay)
A simpler relay version that switches the element fully on when surplus exceeds a set threshold (1kW surplus, for example) and fully off when it drops below. Less precise than proportional control, but cheaper.
- Installed cost: approximately $200-350
How much can a solar diverter save in Perth?
Worked example: 6.6kW system, north-facing, no battery
| Annual solar generation | approximately 9,500 kWh |
| Self-consumption (used directly) | approximately 3,500 kWh |
| Net export | approximately 6,000 kWh/year |
Without a diverter, a 3.6kW hot water element running 1.5 hours a day (5.4 kWh/day, 1,971 kWh/year) is typically on an overnight timer. On the A1 tariff, that's 1,971 x $0.3326 = $656/year just for hot water.
With a diverter, the element runs on surplus solar during the day instead. Perth's sunny months (September to April) provide reliable surplus; winter generates less, but the diverter still captures whatever surplus is available.
Not all 1,971 kWh will be divertable (cloud, timing, and system factors all eat into it), so a realistic annual diversion is more like 1,400-1,700 kWh/year. Taking 1,500 kWh as a representative figure: 1,500 x ($0.3326 - $0.02 DEBS) = 1,500 x $0.3126 = approximately $469/year.
At a single-phase installed cost of $450 to $650, that's a payback of roughly 12 to 17 months. On a three-phase install at $850 to $900, the same saving takes closer to 22 to 23 months.
Solar diverter or home battery: which should you buy first?
If you're weighing up a solar diverter against a home battery as your next investment:
| Solar diverter | Home battery (10kWh) | |
|---|---|---|
| Installed cost | $200-900 | $9,500-14,500 |
| Typical payback | 1-2 years | 5-14 years |
| What it does | Heats hot water for free | Stores solar for evening peak avoidance |
| WA rebate | No | Yes ($1,300) |
| Works without the other | Yes | N/A |
For most Perth households with a resistive electric hot water system, the diverter is the better first step: it pays back far quicker than a battery. A battery may be the right next move once the diverter's in place. For the full number breakdown on battery payback, see is a home battery worth it in Perth in 2026?
What hot water systems work with a solar diverter?
Works well:
- Electric storage hot water with a resistive element (252L, 315L: the most common Perth setup)
- Any wattage element, since the diverter matches its power output to available surplus
Doesn't work, or works differently:
- Gas hot water: there's no electrical element to divert to.
- Heat pump hot water: some diverters can control a heat pump via a relay, but it's more complex. Heat pump compressors run best at constant power, not throttled up and down with a moving surplus. See solar diverter vs heat pump hot water: making the right choice for Perth homes if you're weighing the two up, or our complete guide to heat pump hot water in Perth if you're starting from scratch.
- Solar thermal hot water (separate roof collectors): these already have their own solar heat source and don't use grid electricity for heating (the electric element is backup only).
How does a solar diverter work with Midday Saver?
Under Midday Saver, the 9am-3pm window costs just 8.85c/kWh. That changes the maths on diverting:
- Without Midday Saver: 33.26c avoided minus 2c lost export = 31.26c/kWh saved.
- With Midday Saver (9am-3pm): 8.85c avoided minus 2c lost export = 6.85c/kWh saved.
The saving shrinks during the super off-peak window because grid electricity is already cheap there. A diverter earns the most on the A1 tariff. On Midday Saver, it also does well during the evening peak (3pm-9pm), where the export rate rises to 10c/kWh: any lingering solar surplus there saves 55.33c minus 10c = 45.33c/kWh.
For Midday Saver households, a diverter is still worth having, just with a longer payback than on A1: cheap midday electricity narrows the value of every diverted kilowatt-hour. For the full tariff comparison, see Midday Saver vs A1: which Synergy tariff actually saves you money?
Diverter product prices are indicative for Perth mid-2026. Savings figures are worked examples, not guaranteed outcomes, and assume the A1 tariff at 33.26c/kWh effective 1 July 2026. Your own saving depends on your system size, orientation, and hot water usage.
Money-relevant figures in this article are checked against primary sources. Here’s how we check our facts.
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