inverter

[windspeed]

would a 4000 watt inverter running a 300 watt load be less efficient than a 300 watt inverter running the same load

and which would use the most in standby  

windspeed

[ghurd]

Yes?

"the most in standby" makes it all a guess.

Most inverters are more efficient at 85~95% of full load.

I have seen 300W inverters take >3A no-load, and 400W inverters take under 80ma.

I never tested a 4000W 12V inverter, or UK type inverters.

If it was 400W inverter and 300W load, I would use a 400W inverter.

G-

[wpowokal]

Provided said inverter can start the applied load/s.

allan

[electronbaby]

haha yes, provided the inverter can start the load. You never want to run anything full tilt. Especially one of those cheap Chinese jobs. There are basic rules of thumb to inverter efficiency, but it depends on if you will run the load 24/7, or just once in a while, which would lead you to looking closely at standby efficiency.

Basically, it depends on what you are trying to accomplish.

[windspeed]

If I want to run 300 watt for 3 hours and 3000 watt for 3 hours would I be more efficient with two separate inverters at my batteries

how would that work with my long connection cable from my batteries to my house

would I need to switch between them manualy

or run two separate cables

windspeed

[mixerman]

I supose what this means is , to be efficent it would be a good idea to have afew differet size inverters.

I just got the Vector 1000 w inverter (VEC049), the box says it draws .6 amps with no load! The instructions says  " Max. efficiency + 90% " , my best guess at this is to use up the stored energy at a rate equlivant to the 90%, but this will limit, or shorten usage time.

beginner learning here!

mixerman

[wpowokal]

You need to look at the inverter specs to see at what load max. efficiency is, I suspect it is at 40-50% load.

allan down under

[wpowokal]

I use a 3Kw inverter, at this moment, 10PM, it's sypplying 320Watts, it has a maximum efficiency of 94% @ 25% LOAD.

I would not use seperate inverters, if you did they could not both be connected to the same AC cable at the same time, unless they were disigned to be stacked, that is both units are syncrinised so the AC wave form is the same. In that case one inverter would provide the time base for both, but I suspect this does not apply to cheep inverters.

Bottom line look at the specifications of the inverters you are planning to buy.

allan down under

[Opera House]

I use a Harbor Freight 2,000/4,000W inverter to run a refrigerator.  It takes that to start the compressor even though running it is about 100W.  I disconnect the fans since running load is minimal.  Many inverters have 3 or 4 fans and they take about 200mA each.  I tested another 2KW inverter running a couple CFL under 100W and running loss was about 7W.