Gridly
Controlled Load
A separately metered electricity tariff - typically 8–15¢/kWh - that only supplies power during off-peak periods (usually overnight). Used almost exclusively for electric hot water systems. Controlled load 1 typically runs overnight; controlled load 2 runs during longer off-peak windows.
How it works
Controlled load (CL) is a separate circuit in your switchboard that the network can turn on and off remotely via a ripple control signal on the power line (or, increasingly, a smart meter command). Appliances wired to the CL circuit - almost always electric hot water systems - only receive power during the designated off-peak window.
The benefit is a much lower rate: controlled load tariffs typically range from 8¢/kWh to 15¢/kWh, compared to 28–42¢/kWh on standard rate. This makes electric hot water relatively cheap to run despite being a high-consumption appliance (typically 1,500–3,600W).
Controlled Load 1 (CL1): Usually 7–8 hours overnight, often around 10 pm–6 am. The exact timing is set by the network operator. Most 250–315L hot water systems can heat a full tank in this window.
Controlled Load 2 (CL2): A longer off-peak window of 10–18 hours per day, which may include daytime periods. Available in some network areas. The rate is slightly higher than CL1 because the window is longer and may include some shoulder periods.
The solar interaction
Standard electric hot water systems on controlled load heat overnight - which is exactly when your solar panels aren’t generating. This creates a suboptimal situation: you’re buying cheap off-peak electricity to heat water when you could be using free midday solar instead.
Several options address this:
Hot water diverter: A device (Catch Power Green, iBoost, Suntrix) that sends excess solar to the hot water element during the day, reducing or eliminating controlled load usage. Costs $300–$600 installed.
Smart timer: Shift the hot water system’s heating window to 10 am–2 pm solar peak rather than overnight. Requires switching off CL tariff (you’ll pay standard rate for the hot water usage, offset by not buying CL electricity).
Heat pump hot water system: Replaces the resistive element with a heat pump that uses 60–75% less electricity. The economics of this upgrade have improved significantly since 2022 with state government rebates in VIC, NSW, and QLD.
Solar diverters vs controlled load - quick comparison
| Controlled Load | Solar Diverter | |
|---|---|---|
| Rate | 8–15¢/kWh | ~0¢ (own solar) |
| Heating time | Overnight | Midday |
| Upfront cost | Nil | $300–$600 |
| Works without solar | Yes | No |