What Is Inverter Idle Consumption?
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What Is Inverter Idle Consumption?
Inverter idle consumption is the power an inverter uses while it is switched on and supplying no load, or only a very small one. Even when nothing is plugged in, the inverter’s electronics keep running, and that uses energy from the battery. Over a day or a week, that energy adds up. For the Victron Energy SUN Inverter, the manual describes an ECO mode, also called search mode, that lowers this draw by letting the inverter sleep and check for a load at intervals. This page explains the idea and the figures the manual states.
Quick answer
- Idle consumption is the power drawn from the battery when the inverter has no meaningful load.
- The SUN Inverter manual lists zero load power of 4.2 W for the 12/250 model and 5.2 W for the 24/250 model.
- In ECO mode, the manual lists a default zero load power of 0.8 W for 12/250 and 1.3 W for 24/250.
- ECO mode switches the inverter to search state when the load is very low, and it checks for a load about every 3 seconds.
What idle consumption is
An inverter converts DC from the battery into AC. To do that, it needs internal circuits to be powered at all times when it is on. Those circuits draw a small amount of power even when the output is idle. The total is the idle or no-load draw. It is measured with no load connected, and it is separate from the power the loads themselves draw when they are running.
The distinction matters for a battery system. A battery that powers a load all day is affected by the load. A battery in a system with an inverter that is left on overnight is also affected by the idle draw, even when no appliance is running. The idle draw is a steady drain, and it is the reason many inverters have an idle-saving mode.
The figures in the manual
The technical specifications section of the SUN Inverter manual lists two zero-load figures for each model in its table: the zero load power, and the default zero load power in ECO mode. The numbers for the two models shown are:
| Model | Zero load power | Default zero load power in ECO mode |
|---|---|---|
| SUN Inverter 12/250 | 4.2 W | 0.8 W |
| SUN Inverter 24/250 | 5.2 W | 1.3 W |
Source: SUN Inverter manual, section 6.1 (listed in the source list at the end of this page). The ECO row is labelled as a default, so the value on a unit depends on the settings it has. The same section lists a peak power of 400 W for both models, which is a different figure and is covered in our explainer on overload protection.
How ECO mode works
The configuration and operation sections of the manual describe ECO mode, which the manual also calls search state. The configuration section says the inverter switches to search state when there is no load or a very low load. In search state, the inverter is off most of the time and switches on every 3 seconds for a short period. The manual describes the search interval as adjustable. Operation section 5.1.1 uses the same description: the inverter switches on, briefly, every 3 seconds to detect a load.
The operation section also describes what the green power LED does when the inverter is in search state. It states that the inverter has been switched to ECO mode and is in search state, and that this occurs when the load is lower than the wake-up power setting. The LED pattern is therefore a useful sign that the inverter is idle-saving rather than faulty.
The ECO settings
The configuration section gives the ECO settings with their defaults and ranges:
- Wake-up minimum power: default 14 VA, range from 14 VA up to the inverter rating.
- ECO mode search interval: default 3 s, range from 0 to 64 s.
- ECO mode search time: default 0.16 s, range from 0.08 to 5.00 s.
The wake-up power is the load the inverter needs to see before it stays on. A load below the wake-up power keeps the inverter in search state, and the inverter’s brief checks are the only time it draws more than its idle figure. The search interval sets how often it checks. The search time sets how long each check lasts.
What the ECO settings mean in practice
The trade-off is simple. Searching saves idle power, but it means the inverter does not supply power continuously when the load is small. A device with a very small standby draw, such as a clock or a phone charger at light load, may not keep the inverter awake. The operation section describes a case where the inverter keeps cycling on and off with a light load. In that case, the manual’s approach is to raise the load or change the wake-up setting. Changing the wake-up power changes the threshold, so it should be set with the loads you actually run in mind.
A shorter search interval wakes the inverter sooner, which helps with small loads, but the inverter then spends more time checking. A longer interval saves more power, but a small load may go unnoticed for longer. The ranges above show the limits the manual allows.
How to estimate the daily cost
You can estimate what an idle draw means for a battery over a day. The arithmetic is: watts multiplied by 24 hours gives watt-hours per day. For example, the manual’s 4.2 W zero load figure for the 12/250 model, run continuously with no ECO saving, would be 4.2 multiplied by 24, or 100.8 Wh per day. The ECO default of 0.8 W for the same model would be 0.8 multiplied by 24, or 19.2 Wh per day, but that figure assumes the inverter sits in its ECO default the whole time, which is a simplification. Real use will vary with the loads and the settings. The calculation shows the scale of the difference, not a measured result.
What to check on your system
- Note whether ECO mode is enabled and what the wake-up power is set to.
- Check the LED pattern when no load is connected, since a slow short pulse is the manual’s sign of search state.
- Do not set the wake-up power so high that your smaller loads cannot wake the inverter.
- If the inverter cycles on and off with a light load, adjust the load or the wake-up setting as the manual suggests.
How we chose
The idle figures on this page are the zero load and ECO default values in the technical specifications section of the SUN Inverter manual for the 12/250 and 24/250 models. The ECO description and settings come from the configuration section, and the search state description and LED behaviour come from the operation section. All three pages were opened on 2026-10-27 from the HTML5 edition, © 2022. The daily arithmetic is ours and is labelled as such.
What we could not verify
- The pages cover the 12/250 and 24/250 models in the technical specifications. We cannot give zero load figures for other models from these sources.
- The pages show no revision number, so the figures are as published on the pages on the date opened.
- The ECO default figures are defaults. The actual idle draw of a unit depends on its settings and its firmware.
- The sources we opened do not give a measured idle figure for any real installation.
Mistakes to avoid
- Reading the zero load figure as the total battery drain. The battery also supplies loads and losses in the cables.
- Turning ECO off to avoid cycling without checking the battery budget.
- Setting the wake-up power so high that small loads never wake the inverter.
- Assuming a constant 4.2 W or 5.2 W draw when ECO mode is on.
FAQ
What is the idle draw of the SUN Inverter 12/250?
The manual lists a zero load power of 4.2 W for the 12/250 model. With ECO mode at its default, the manual lists 0.8 W.
What is the idle draw of the SUN Inverter 24/250?
The manual lists a zero load power of 5.2 W for the 24/250 model. With ECO mode at its default, the manual lists 1.3 W.
What does search mode mean?
Search mode is the ECO state in which the inverter is off most of the time and checks for a load every few seconds. The manual says it switches on every 3 seconds for a short period by default.
Why does the inverter click on and off?
It is likely cycling in search state. The manual says that when the load is lower than the wake-up power, the inverter stays in search state. Raising the load or changing the wake-up setting, as the manual suggests, can stop the cycling.
Should I always turn ECO mode on?
It depends on the loads. ECO saves idle power but may not wake for very small loads. Check the wake-up power against the loads you run.
Bottom line
Idle consumption is the power an inverter draws with no load, and ECO search mode reduces it by checking for a load at intervals. Use the manual’s zero load and ECO figures for your model, set the wake-up power with your smallest loads in mind, and check the LED when nothing is connected.
Related guides
Sources
- Victron Energy, “SUN Inverter Manual” (HTML5 edition, © 2022), section 4 Configuration, 4.2 ECO mode and ECO settings. https://www.victronenergy.com/media/pg/Sun_Inverter/en/configuration.html. Opened 2026-10-27.
- Victron Energy, “SUN Inverter Manual” (HTML5 edition, © 2022), section 5 Operation, 5.1.1 ECO Mode and 5.3 Power and Alarm LED definitions. https://www.victronenergy.com/media/pg/Sun_Inverter/en/operation.html. Opened 2026-10-27.
- Victron Energy, “SUN Inverter Manual” (HTML5 edition, © 2022), section 6.1 Technical specifications SUN Inverter (zero load power and ECO default zero load power, 12/250 and 24/250). https://www.victronenergy.com/media/pg/Sun_Inverter/en/technical-specifications.html. Opened 2026-10-27.
