Solar hot water diverters in Perth: redirect excess solar instead of exporting at 2c

Under the Distributed Energy Buyback Scheme (DEBS), excess solar you export to the grid earns 2c/kWh during the off-peak period (9pm to 3pm). For most Perth households, this off-peak window covers the majority of midday solar generation — the period when panels are producing the most.

At A1 tariff, every kWh you self-consume saves 33.26c instead of earning 2c. The gap is 31.26c per kWh.

A solar hot water diverter exploits this gap: it monitors your inverter output and diverts excess solar generation to your electric hot water system's resistive element instead of letting it export. The water heater becomes a thermal battery, storing solar energy as hot water rather than sending it to the grid.

How a solar diverter works

A solar diverter sits at your switchboard and measures:

• How much solar your inverter is generating
• How much electricity your house is currently consuming

The difference — the amount that would otherwise export to the grid — is redirected to the hot water element at a controlled rate.

The key: it matches supply. Rather than switching the hot water element fully on (which would draw 2.4–3.6kW from a standard element), the diverter uses power electronics to throttle the element to exactly match the surplus solar power. If you have 1.2kW of excess solar, the diverter feeds 1.2kW to the hot water — not 3.6kW (which would pull grid power to make up the difference).

This way, the hot water element only ever runs on surplus solar. No grid electricity is imported. The element runs longer at lower power but achieves the same heating effect.

Main products in Australia

Catch Power (Green/Blue/Red): Australian-designed and manufactured. The most common solar diverter brand in Perth. The Green model is the standard single-element residential product ($500–$700 installed). Can monitor via app. Good local support.

iBoost (Marlec): UK-designed, available in Australia. Requires a compatible "iBoost Buddy" sensor clip to measure grid power. Older product with a simpler interface than Catch Power but reliable. Typically $450–$650 installed.

Eddi (myenergi): UK-designed, growing Australian availability. Part of the myenergi ecosystem (which includes the Zappi EV charger). More sophisticated than the basic diverters — can manage multiple loads (hot water, EV, pool pump) with priority ordering. Typically $600–$900 installed.

SolarEdge Energy Bank / StorEdge: SolarEdge inverter users can configure self-consumption routing through the inverter platform, effectively achieving similar results without a separate diverter device. Only applicable if you have a SolarEdge inverter.

Cost vs alternatives

| Option | Capital cost | What it does | |---|---|---| | Solar diverter (Catch Power) | $500–$900 installed | Redirects excess solar to existing resistive HWS | | Heat pump hot water | $2,500–$4,500 installed | Replaces resistive HWS; ~3× more efficient | | Home battery (10kWh) | $9,000–$14,000 installed | Stores solar for evening use across all loads |

A solar diverter is not a replacement for a heat pump hot water system or a battery. It's a targeted, low-cost intervention that specifically addresses the "export 2c instead of saving 33c" problem for hot water heating.

The economic case: A Perth home exporting 5kWh/day of surplus solar earns $0.10/day at 2c (off-peak). If a diverter redirects 3kWh of that to hot water, it avoids 3kWh of grid electricity that would have been used for hot water overnight — saving 3 × 33.26c = ~$1/day or $365/year at A1 tariff.

Payback period: $700 installed ÷ $365/year = approximately 2 years.

Comparison with heat pump: A heat pump hot water system uses 3× less electricity for the same heating output. If you're replacing an ageing resistive system, a heat pump is the better long-term investment — it improves efficiency with any electricity source, not just solar surplus. A diverter doesn't change efficiency; it only redirects the source.

Comparison with battery: A 10kWh battery stores surplus solar for evening consumption across all loads. The battery's value is broader but the upfront cost is 10–15× higher. The diverter makes economic sense as a standalone low-cost option, or as a complement to a battery if you have more solar surplus than the battery can absorb.

When a diverter makes sense

A solar diverter is a good fit when:

• You have an existing electric (resistive) hot water system in good condition — not worth replacing yet
• Your solar system is 6.6kW or larger — enough midday surplus to heat water regularly
• You're not planning to add a battery immediately — the diverter captures the surplus until then
• You're on A1 tariff, not Midday Saver — on Midday Saver, the super off-peak rate is 8.85c, so the self-consumption saving drops to 6.85c vs 2c export (still positive, but smaller benefit)

A diverter is less compelling when:

• You already have a heat pump hot water system (heat pumps are already efficient; a diverter on a heat pump adds little)
• You're on Midday Saver with high evening peak usage — a battery to cover the 55.33c/kWh peak window delivers much more value per dollar than a diverter
• Your existing hot water system is due for replacement anyway — better to replace with a heat pump

Installation requirements

• Any standard single-phase electric hot water system with a resistive element (the element itself needs no modification)
• A compatible solar inverter (most diverters work with any inverter brand via clamp meter sensing; some have direct CT integration)
• Installation by a licensed electrician — typically 2–3 hours
• Some diverters require a separate current transformer (CT) clamp on the grid connection point

If your hot water system is on a controlled load (off-peak) tariff circuit (a common arrangement in older Perth homes), discuss with your installer how the diverter interacts with the existing meter configuration.

Product pricing is indicative mid-2026 and varies by installer. DEBS rates and A1 tariff effective 1 July 2026. Savings calculations are illustrative — actual savings depend on your solar generation pattern, hot water usage, and tariff.