Quiecent wattage Phoenix inverter smart too high

Been meaning to post about this for a while actually, because I've had a similar head-scratcher on my narrowboat setup.

Running a Victron Phoenix Smart 24V 800W and the spec sheet quotes around 8W quiescent. When I put my clamp meter on it with nothing connected on the AC side — not a single load, ECO mode off — I was pulling closer to 18-20W at resting voltage. That's more than double what Victron are advertising.

Now I know there's always going to be some variation, and measuring DC-side wattage isn't perfectly clean (voltage sag, meter accuracy, etc.), but this felt significant enough to dig into.

A few things I've since wondered:

• Is the quoted figure only valid at a specific battery voltage? I've seen some datasheets where quiescent power is measured at nominal, not float.
• Does firmware version play a role? Mine hadn't been updated in over a year when I first noticed this.
• Could the VE.Direct or Bluetooth stack add to idle draw in ways the headline spec doesn't account for?

After a firmware update via VictronConnect it did drop slightly, but still not down to spec.

On a static caravan or boat where your battery bank isn't huge and you're watching every watt-hour, an extra 10-15W at idle overnight is genuinely meaningful — that's potentially 120-180Wh you weren't planning for.

Anyone else measured their Phoenix idle draw properly? Would be good to know if this is widespread or just something quirky with certain units. And has anyone actually had Victron or a dealer acknowledge it?

@Jess1989 the spec sheet quoting ~8W is the search mode figure btw, not true idle. Actual quiescent with search mode off is more like 11-13W in my experience — Victron's own docs bury this distinction a bit.

On my cabin setup I saw similar numbers until I realised the VE.Direct bluetooth dongle was adding another watt or two on top. Worth checking if you've got any accessories hanging off it.

Also — are you measuring at the inverter terminals or at the battery? Wiring losses between the two can skew readings noticeably, especially if your cable run isn't perfectly sized.

@Jess1989 worth checking your DC wiring too — I had a similar situation on my narrowboat where measured quiescent was way above spec, turned out to be a loose negative connection on the DC bus causing parasitic resistance heating. The inverter's internal monitoring was seeing it as load.

Also, the Phoenix Smart's Bluetooth module itself draws a small but non-trivial amount continuously. If you've got VictronConnect actively polling via BT, that adds up.

What's your battery bank? I found my Fogstar Drift 24V cells have slightly different internal resistance characteristics that were confusing my readings initially — the clamp meter placement relative to the BMS was giving me ghost figures.

Try isolating the inverter on its own short cable run directly at the battery terminals and remeasure. Sometimes the installation itself is the variable, not the unit.

Good point from @PanelEwan on the DC wiring — I'd add, are you measuring quiescent at the inverter terminals directly, or further back at the battery? Voltage drop across undersized cable can skew your readings if you're calculating consumption from battery voltage rather than measuring current directly.

On my van build I use a cheap clamp meter directly on the DC feed to the inverter to get a clean quiescent figure. Removes any wiring variables from the equation.

What gauge cable are you running, and how long is the DC run from your batteries to the inverter? On a 24V system it's less critical than 12V, but still worth ruling out before assuming the inverter itself is misbehaving.

@Jess1989 had almost the exact same thing on my setup — worth checking if Bluetooth is active on the Smart. Leaving the VictronConnect app connected in the background keeps the comms module powered and that alone can add a few watts to your idle draw. Bit annoying really.

Also — is your unit warm? I noticed mine draws noticeably more in a cold engine bay until it thermals up properly. Not massive but it adds up overnight.

Try disabling Bluetooth via the rocker if you're not actively monitoring and see if your figures drop. Mine went from ~15W idle down to closer to 11W just doing that.

What @DownsExplorer said about Bluetooth is the real culprit nine times out of ten — mine was doing the same thing on the boat until I realised the VictronConnect app was sat open on my phone basically polling the inverter all day like a nosy neighbour.