How efficient are inverters when not powering full capacity?

[benjamino]

Getting fed up of building my own 12v power supplies for my laptops, speakers etc, and am thingking about getting an inverter. Don't need pure sine but would like to know how eficient they are when not under full load, relative to their rating.

 

So for example how many watts would a 350 watt inverter use when powering an 80 watt device? Would a 1000 watt inverter use any more power to run the same device?

 

Thanks,

[nb Innisfree]

Getting fed up of building my own 12v power supplies for my laptops, speakers etc, and am thingking about getting an inverter. Don't need pure sine but would like to know how eficient they are when not under full load, relative to their rating.

 

So for example how many watts would a 350 watt inverter use when powering an 80 watt device? Would a 1000 watt inverter use any more power to run the same device?

 

Thanks,

 

Good quality inverters are quite efficient, our 3 KW Victron Multiplus is claimed to be 94% efficient, if I turn on a 230v 20 watt light it registers 0.7A on the battery monitor and turning on the other 13 one by one the amps stay in proportion, so it seems to be 94% efficient at various loads.

Edited August 16, 2009 by nb Innisfree

[Gibbo]

You need to look at an inverter efficiency gragh.

 

When powering nothing they stil use power so quite clearly the efficiency at zero load is zero. As the power is increased the amount wasted is reduced.

 

But you really need to look at an efficiency graph to understand the extent.

 

Gibbo

[benjamino]

You need to look at an inverter efficiency gragh.

 

When powering nothing they stil use power so quite clearly the efficiency at zero load is zero. As the power is increased the amount wasted is reduced.

 

But you really need to look at an efficiency graph to understand the extent.

 

Gibbo

 

Thanks - where would I find one of those? Can't seem to see one on Victron’s website.

[blackrose]

You need to look at an inverter efficiency gragh.

 

When powering nothing they stil use power so quite clearly the efficiency at zero load is zero. As the power is increased the amount wasted is reduced.

 

But you really need to look at an efficiency graph to understand the extent.

 

Gibbo

 

My understanding is that semi (or psuedo) sinewave inverters are generally more efficient than pure sinewave. Assuming the appliances one wishes to run don't require pure sinewave.

Is this correct?

[benjamino]

My understanding is that semi (or psuedo) sinewave inverters are generally more efficient than pure sinewave. Assuming the appliances one wishes to run don't require pure sinewave.

Is this correct?

Sterling Power’s website seems to indicate that. They're supposed to be 85-95% efficient. I can only find the max-efficiency for the Victron sinewave inverters and that is 89% for a 12v 350VA inverter. So not a great deal in it, but then again it's hard to say what loads would generate those levels of efficiency (what is the Victrons lower efficiency theshold?) and if there's a difference in the efficiency curve gibbo mentions between sinewave and modified sinewave inverters.

 

Incidenatly my 12v amperor stabilizer only claims to be >80% efficient so if need a stable 12v it's probably going to about the same as using an inverter and then a normal spower supply?

[Justme]

My Victron quotes 93% max & 6-10W on economy at no load.

[benjamino]

Just heard back from Sterling Power - Charles Sterling said:

---

I think you are using the wrong words.. Quasi sine inverters take about 0.8

amps to exsist ( the quiescent current ) so it does no matter if its a 350

or a 1800 watt inverter they will both take the same quiescent current to

exists. After that they are both 90% efficient. So it actually make no

difference to the efficiency which unit you use

---

So seems like they're all much the same at all loads after the power they need to exist is taken into account - Gibbo - does that sound incorrect?

[Gibbo]

So seems like they're all much the same at all loads after the power they need to exist is taken into account - Gibbo - does that sound incorrect?

 

Yep it's wrong.

 

The no load draw of a pure sinewave inverter is higher than a modified sinewave inverter.

 

The efficiency of a pure sinewave inverter is lower than a modified sinewave inverter. There's not much in it, about 5% usually.

 

Gibbo

[nbfiresprite]

Getting fed up of building my own 12v power supplies for my laptops, speakers etc, and am thingking about getting an inverter. Don't need pure sine but would like to know how eficient they are when not under full load, relative to their rating.

 

So for example how many watts would a 350 watt inverter use when powering an 80 watt device? Would a 1000 watt inverter use any more power to run the same device?

 

Thanks,

 

My Prosine has 93% efficiency and when there is no load it reverts to power save mode where it draws only 20 Ma, it does mean a 5 second delay when it powers up to full load. When the power save mode is switch off it draws 0.4 A.

 

 

Firesprite

 

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