Why the laser focus on Idle Power?

Idle Power... why the obsession? How many hours a day is your system idle? On a very small system, sure, it makes a difference. In a whole house or a system that is powering stuff 24/7 idle power means nothing... what should be noted is power consumption under load if that is what the system is doing most of the time.

In reading threads, I see people touting low idle power... if your system is running so infrequently that idle power is an issue... I just don't know what this is about??

In researching a few years back on how I was going to build my system, I realized that idle power wasn't an issue, in any way. My system was almost never going to be idle. and even if it were idle 8 hours a day, the savings difference would be what? 40 watts?? so I save 320 watts out of my 15kw hour battery??

So then... if your system is doing work most of the time.. idle power consumption seems irrelevant to me.

Idle power is a factor 24/7. That's what it takes your inverters to run

I've seen this a couple times. Idle power doesn't mean when idle, it means the overhead.
My Sol-Ark is 60 watts. That's 1.44kW a day. I'm not off grid, so no big deal. But for those who are, especially with small battery banks, a few cloudy days eats a lot of battery.

By idle power they mean the quiescent usage of the inverter just to power itself; so 24/7.

My Solis only uses 30W, so that's 720Wh per day. But if you had a pair of inverters each with 100W idle usage (as some are), then that's 4.8kWh a day.

less wasted power equals less heat. It also gives you more coverage for days of backup when the sun isn't shining. The less waste it has the bigger your battery effectively becomes.

It's idle power + whatever other power your house needs.. so it isn't just "when your system is idle". There are some really high "idle" systems that are 200W so that's 4.8kWh extra per day no matter what you have to generate. A higher quality system could easily be only 1.4 kWh per day.

Excellent question.
And the misunderstanding is frequent.

The big deal is total operational time, and how much solar needed to offset the drain.

Unless you shut off your inverter when not in use, a drain on constantly is additional storage capacity you have to plan for, and additional solar needed to recover lost Wh's when sun shines again.

5kWh from a pair of inverters means an entire 100Ah rack battery dedicated to covering the drain, and 12 additional 400W solar panels just to replace what it used up...
Each day... so, if you are 100% off grid, and you include 3 days of capacity for bad weather days, that is THREE rack mount batteries JUST to cover the constant drain of the inverter connection...

ALWAYS factor in the overhead drains...

100 watt idle power is 2.4Kwh or 2400 watts of charging for an hour.

I have a 2400 watts array. When in rains, I get about 250wh for the day so I would need to run the generator for 1.2 hours @ 70 amps charge (24 volt) just to compensate for idle consumption and nothing else.

Or assuming my array had 100% output, 1 hour of the charging day would be dedicated just to the waste heat produced by the idling inverter.

If you have power to waste, it's not a big deal.

2.4 kwh hours of waste is 2.5 305ah cells as well.

LOL... 7 answers all saying the same thing. See, we do agree about some things on here

It takes power to make power. Idle loss is just one of the things you take into account when designing your system. Sorta like buying groceries for the week. If you only buy for 2 people, and you have 3 show up, arguments over portion size gets intense.

However trying to compare one system's idle loss to another can be very difficult because the darn manufacturers tend to not be totally honest or use the same measuring stick.

Power self consumption used during operation is frequently not mentioned but it more often is a real concern.

Also, some of us just hate waste. Imagine opening up a closet, turning on a 100 watt light bulb and then shutting the closet and never opening it again.

That little light, costing you 25 cents a day to run on grid or absconding with 2.5 305ah cells worth of energy per day behind a closed door, going to waste..never being used...akin to a water pipe just leaking water into the ground or perhaps a faucet drip....drip....drip....drip...all day, all night...you can't sleep....going insane.

Yeah...that idle consumption.

To say the same thing again slightly differently:

OP's model:

40w idle power, with 100w load on it, equals not idling, so 100w load.

Community model:

40w idle power, with 100w load on it, equals idle power plus load, so 140w load.

The reality is actually probably somewhere in between the two simplifications, and each inverter is going to have a different profile of how much of the idle power does or doesn't get absorbed into the loaded power. It might end up being 40w idle and 120w loaded with a 100w load.

So if you consider that your inverter will always be loaded, mine is, you'd really want to look at a detailed efficiency curve to compare two models. Which sort of speaks to OP's point, but we mostly agree that idle power is going to be a predictor of how good that curve is. The efficiency of any inverter at idle is going to be negative infinity.

I have nothing to add. lol

Let's give a real world example... It is my friend's cabin. He just needs enough electricity to run a mini fridge-freezer(average 35W), charge a mobile phone and run a couple of led lights. His power requirements are fully met by a single 400W panel and a 100ah 12V battery. But the compressor startup of the fridge requires a 1kW inverter. So now he has 28W of constant load on top. Essentially another fridge. Running 24/7. Unless he goes and shuts the power down.

This means that if he fridge is off this will drain the battery on its own in 3 days. He keeps a gas generator just in case there is bad weather 3 days straight.

I have 2 EG4 6000EX low frequency inverters.
They have a LARGE idle consumption.
I generally only run on 1 inverter, and have 12 ea. 5.12 kWh batteries, but they basically eat a battery per day just on idle consumption.
That's a lot.

Another real world example:

Honey Badger Ranch "idles" along at about:

273W total DC draw

124W DC to provide 87W AC output (70% efficient at such low power)
95W of DC loads (Starlink V1, mini PC, 2x routers)
54W of inverter idle load.

Idle eventually gets rolled into efficiency at higher power settings with peak efficiency at 30% of rated.

my first attempt at diy solar was 1200W array with an older aims 6kw inverter/charger with a 180W idle. the panels produced 4800Wh/day, the inverter just sitting there doing nothing consumed 4400Wh/day, leaving basically no energy to run house loads. even if i maxed out the built in 60A solar charger with more panels making 6kWh/day, that would only leave 1500Wh/day for house loads, what a ridiculously stupid design

i ended up tearing that inverter apart replacing the guts with an egs002 board, new inverter now has a 20w idle, uses only 500Wh/day. massive difference

i wish somebody had told me about idle power back when i bought the aims, would not have wasted $2k

Some inverters claim a sleep type mode when there is no draw. I'm thinking the clock on the microwave, or whatever, is always on. If you have 2 inverters in parallel, the ability to put the slave in deep sleep is nice.

DIYrich said:

Some inverters claim a sleep type mode when there is no draw. I'm thinking the clock on the microwave, or whatever, is always on. If you have 2 inverters in parallel, the ability to put the slave in deep sleep is nice.

Click to expand...

Sadly with many cheaper models (like the one my friend had before) the sleep/power saving doesn't really work, or works only when you try pulling few hundred Watts).

The real "sleep mode" is when you flip the physical off switch. Which doesn't really turn the entire device off. Only the inverter portion. So it still charges the battery from the panels. In this mode it only idles at a couple of Watts, but there is no AC of course.

Supervstech said:

5kWh from a pair of inverters means an entire 100Ah rack battery dedicated to covering the drain, and 12 additional 400W solar panels just to replace what it used up...
Each day... so, if you are 100% off grid, and you include 3 days of capacity for bad weather days, that is THREE rack mount batteries JUST to cover the constant drain of the inverter connection...

Click to expand...

You might re-think the wording here. People keep intermingling KWH and kW and W it gets weird. 12 panels * 400W = 4800W * 1 hour of sunshine is ~5KWH needed to recharge that battery. Or more accurately, TWO (2) additional 400W panels for 6 hours (a solar day). Perfect days and perfect sunshine and perfect panels and all that, but You only need to buy 2 panels not 12.

I know some folks were mentioning in various threads of aio's approaching100W of overhead, but I don't think any of the stuff you get today is gonna be anywhere close, and if I recall the units in question dropped dramatically with a firmware upgrade. TWO inverters with a 100W overhead each need 2400WH * 2 = 4800WH. Realistically I think my two AIO's pull maybe 50-70W combined, and they are capable of 24000W of output. Probably a good idea to know about what it is, but reality is you have to simply plan for whatever the overhead is because frankly you are going to have overhead and your system output needs to be whatever order of magnitude higher than the overhead to meet your demand/needs.

The AIO is oviously going to use more power internally while it's inverting, and keeping relays on and such than when it is in 'standby'. The idea of course is to be "on" not dead in the water.