An inverter running with nothing connected isn't free — it's converting DC to AC and maintaining voltage regulation, which uses power even with zero load. Understanding this helps you manage your battery more precisely.
Typical idle draws
| Inverter size | Typical idle draw | 8 hours overnight |
|---|---|---|
| 400–600W budget inverter | 5–15W | 40–120Wh |
| 1,000W pure sine | 10–20W | 80–160Wh |
| 2,000W pure sine | 15–30W | 120–240Wh |
| 3,000W pure sine | 25–50W | 200–400Wh |
| Victron MultiPlus 12/1600 (ECO off) | ~10W | ~80Wh |
| Victron MultiPlus 12/1600 (ECO on) | ~2W | ~16Wh |
These are typical ranges — check your inverter's spec sheet for the exact "no-load power consumption" figure.
How much does this matter?
On a 200Ah LiFePO4 bank (160Ah usable at 80% DoD = 1,920Wh):
- 15W idle for 24 hours = 360Wh = 19% of usable capacity per day, just from the inverter sitting idle
- 15W idle for 8 hours (sleeping) = 120Wh = 6% of usable capacity
For a van that boondocks heavily, this is a meaningful drain. For a van that parks at campgrounds with shore power most nights, it matters less.
ECO mode / search mode
Many inverters include an ECO or search mode that drastically reduces idle draw by pulsing the AC output at low frequency (typically every 1–3 seconds) to check whether a load has connected. If no load responds, the inverter stays in low-power state.
- Renogy inverters with ECO mode: idle drops to ~3–5W
- Victron MultiPlus with ECO mode: idle drops to ~2W
- Budget inverters without ECO mode: stay at full idle draw regardless
ECO mode works fine for most loads but can cause issues with some electronics that don't respond quickly to the pulsed output. CPAP machines, in particular, sometimes don't start correctly from ECO mode — test yours.
Practical recommendation
Default: Switch the inverter off at the main switch or via a 12V relay when you don't need it — when sleeping (no CPAP via inverter), driving, or if the van is parked and not being used. Install the inverter's remote switch in an accessible location so switching it on/off is convenient.
If you need it always on (CPAP at night, etc.): Enable ECO mode if available. A 2–5W idle draw is acceptable. If ECO mode causes CPAP startup issues, disable it and accept the higher idle draw as the cost of CPAP use.
Size the inverter for your loads: Larger inverters have higher idle draws for the same loads. A 3,000W inverter running a 500W laptop is wasting more idle power than a 1,000W inverter doing the same thing.
Related
Roam Wired
Roam Wired turns campervan research into practical plans. We publish transparent guidance, a free electrical design tool and marketplace resources for UK and US van builders.
About our approach