DC current pull from a 150 w inverter with 14 w load?

I bought a UNI-T UT210E True RMS AC/DC Current Mini Clamp Meter for $35 on EBay. I was surprised how well it measures DC amps at this price point.
No more guessing with this meter.

Normally I would say to estimate DC Current draw divide watts by 10

But at that low a draw the "overhead" of the inverter comes into play so the 1.5 to 2 amp answer is the one I'll second.

The rated watts of an appliance usually state the max. The appliance usually will consume a bit less over the long haul. While conversing in watts seems simple enough, reality involves both voltage and current and as the DC voltage drops the DC amps will rise. This is why the above helpers use voltage and current.
If your appliance uses a wall wart and its rated voltage is in the 12VDC range, I would consider eliminating the inverter. You will get more efficiency & reliability. If your appliance is life support related (CPAP,etc.) a 140 watt inverter is way too close to max for my comfort.

Watts= volts * amps

14w = 12v * amps, solve for amps

This tutorial may be of some help. 12v side of life.

Watts is how most household appliances are rated.
Perhaps someone could provide the formula showing current draw from a 12 volt battery when output is converted to AC with a rated wattage draw?

approximately 12.0A @ 12 Vdc or slightly higher depending on inverter efficiency. :)

1 to 10 is the ratio.
1 amp AC = 10 Amp DC
Rule of thumb

Laptop might only need 1.5A but its wall wart charger is very inefficient. Between the wart losses and inverter losses I wouldn't be surprised to see 2.5-3.0A drawn from inverter. And it gets worse if you want to charge it - the battery losses come into play. In the end, if you are spoiled and want everything wireless, it may cost you 4-5 AH daily to charge the laptop battery, more when it's getting old.

My LP fridge, few LED lights and pump draw 20-25 AH, detectors draw next to nothing. 5 AH would be a significant correction to this budget. Not that I personally am worried about this, with 500W solar harvesting about that much even when it rains all day.

If you are powering something like a laptop, it can change the wattage as the screen gets brighter or dim, so wattage can change minute by minute. Still for battery budgeting reasons, consider it about 1.5 amps per hour, and you will be safe.

The inverter input is about 16 watts with a 14 watt load. If the engine is running, then the input voltage will be about 14 volts, so about 1.1 amps, while on battery power, input can be 12.6 - 11.0 volts. So amperage will go up slightly as the input voltage drops overnight.

Remember that the camper's refrigerator, CO meter and propane leak detectors get together and draw about 35 AH from the battery every 24 hours. So this load will not be significant compared to that load.

I have a pair of 120 watt solar panels, and each can put back about 35 AH daily.

SunELec.com Look for a 12 volt nominal panel with a aluminum frame. They had some 140 watt ones for only $229 last year. The price may have gone down since then.

Good luck,

Fred.

at 90 percent eff, and a fully charged battery
the math says about 1.2 amps

reality is probably 1.5 amps 18~20 watts

that max efficiency is near the max output, operational overhead for the control circuit chips doesn't change so at very small loads the several hundred milli-amps of the control circuits skew the efficiency curve