quick and easy inverter question

My Magnum 3000 has an idle draw of 30w while their 600w inverter draws 10w at idle. However my Magnum 3000 has highest efficiency under load at about 550w draw (90%).

So it does help to use a smaller inverter if you let it idle, but I rarely let mine idle, if I don't need 120v I hit the inverter button on the remote to shut it down completely.

I have propane fridge so if off grid I don't need to let it idle to keep fridge on, even if I did my 300w solar would easily provide the 30w idle power along with other stuff.

I could also do search mode to reduce idle draw to 8w but that causes my microwave clock to blink on and off.

just my humble question here, why get so worked up about a extra few watts whether it be a tiny inverter point of load or a larger inverter whole-house?

if idle current is a huge problem, install a disconnect switch - nobody forcing anybody to leave the inverter on big or small

did I miss something in the original question, or is this thread just weekend entertainment?

Here is some relevant stuff---scroll down to 1136am Update with the surprise ending, and the thread after that.

http://forums.trailerlife.com/index.cfm/fuseaction/thread/tid/28673682/srt/pa/pging/1/page/7.cfm

higher capacity doesn't equal higher idle current draw

differences in features result in differences in idle current draw.

Scott Malkinson wrote:
Does the inverter itself cause any kind of draw?

Yes. Check the specs for any inverter. Look for the 'no load' aka idle draw.

Scott Malkinson wrote:
Ok, didn't think it would matter much. Thanks

The best answer so far is that from road-runner ... any wasted energy is just that - wasted ... and larger inverters will inherently chew up more power just idling than will a much smaller inverter. Ideally you want to match the size of the inverter to the intended load but that can be hard to do if one load is 30 watts while another may be 800 watts. Practically speaking, whether you choose to use one larger inverter for everything or several different sized inverters depends on how you intend to use them ... doesn't make much sense to power your trailer "whole house" with a small 200 watt inverter but it's entirely practical with say 1000 watt or greater. Individual inverters powering individual devices however raises the question as to where you intend to physically locate them in the trailer and how you're then going to get power to them. For many of us this is no solution at all and we'd much rather take any additional loss created by one single larger inverter and keep the wiring simple. In my case, I originally used my 1000 watt PSW inverter "whole house" but have since installed dedicated receptacles inside the camper where I want them, powered directly from the inverter which is only turned on when it's actually in use. Otherwise it's off and drawing no power at all.

As you can see, not such a simple answer as you had suggested in your thread title.;)

In general, the bigger the inverter, the higher the overhead for it to do nothing. There are exceptions so you have to just look at the individual specs and hope they are correct. For example, my 2,000 watt Prosine has an idle draw of about 2 amps, or 24 watts. When you're powering a really small load, or none at all, that's a lot of battery power going up as heat. By comparison, a small inverter might have an overhead of half an amp or less.

Ok, didn't think it would matter much. Thanks

idle draw will be somewhat different but once drawing power it gets real close.

Not enough to matter.

There is a thing about where in the spectrum of wattage the load is wrt the inverter's range, where the load might be in the most efficient spot. Just doesn't matter for any RV short time activity.

So forget the big vs small inverter and that you should have one of each for different sized jobs.

In fact the big inverter with its short fat wires will run small 120v loads with fewer DC amps draw than a smaller wattage inverter with its usually longer thinner wire (as with a Winegard 12v plug in) with the same load.