Idle power draw in "all in one" inverters. - Page 1
Forum section: electronics / general

author: Fflint
author_rank: Frequent Contributor
timestamp: July 07, 2025, 08:02:44 am
content: For anyone who doesn't know an "all in one" inverter is a very popular kind of device that combines functions of an MPPT solar battery charger, an AC grid battery charger, an off grid AC inverter, a UPS with sub half cycle switchover time and an on grid inverter capable of pushing power to the grid.Most often these devices have the following atlrchitecture:- a high voltage DC Bus- on that bus there is a bidirectional HV DC to 52V DC converter for the battery. If the voltage on the bus drops it pulls from the battery, otherwise it charges it.- the MPPT dumps it's power on the same HV bus- a bidirectional inverter/rectifier/booster that powers the HV bus from AC or it can sync with the grid push power to the grid or power the loads in off-grid mode (as well as provide ups function)- an AC transfer switch.All these circuits are well documented online. They are all pretty much the same.They start at 2kW and the biggest go to 20kW now.I'm mainly interested in the idle power consumption in off grid mode at night. This is when mppt is off, AC in side is off and all we have is the inverter running with no load.The idle consumption is about 10W per kW of max power. Sometimes slightly less or slightly more. On my 5.4kW AIO it's 40W, on my 10.2kW it's sometimes up to 120W.I wonder where are these losses coming from. What is the deciding factor? Switching losses? How would one go about lowering them?I have to say this video was instrumental in me thinking about this.https://youtu.be/kzuOezZ_quI?si=DpmjmyN39d69X0zwThe author replaces transistors in this AIO and achieves few percent extra efficiency at load. I wonder if something similar could be done for the switching losses or whatever is the deciding factor in idle current consumption.As for why? Let me say my inverters eat up about 6kWh per 24h in this idle consumption. In the solar season it doesn't mater, but in December 5yere are many days when my pv array doesn't even cover that. So I'm interested in experimenting.Just don't tell me to buy better AIOs. The best available still have 50% of the loss of the worst.

author: brucehoult
author_rank: Super Contributor
timestamp: July 07, 2025, 08:58:08 am
content: Quote from: Fflint on July 07, 2025, 08:02:44 amMy Pecron E3600LFP has a 3600W inverter and all the above, minus grid sync and export, plus a built in 3kWh battery and ability to add four 3kWh expansion batteries.And yes right around 1% idle battery use per hour with zero inputs.As I post this I'm 2 minutes from the end of my evening 5-9 peak electricity price time. It's been running my fridge, computers, internet, and 4kW AC unit just from battery for the last four hours and has 25% battery left. I'll be recovering most of that during my "free hour of power" which is from 10-11 PM. I don't have any solar panels yet, but it's paying for itself with time shifting.

author: Fflint
author_rank: Frequent Contributor
timestamp: July 07, 2025, 02:56:06 pm
content: Yes, they are great. I run my house 100% off grid for 8~9 months in a year thanks to these and how cheap they were (as well as the low cost of LFP and solar). Everything in my house is electric. I use about 1MWh per month.I'm at 53.7 degrees north BTW.If I had a way to lower idle consumption by half without reconfiguring the phases (we have 3 phase here) and swapping inverters that would probably give me an extra month at least.

author: brucehoult
author_rank: Super Contributor
timestamp: July 08, 2025, 03:44:30 am
content: Quote from: Fflint on July 07, 2025, 02:56:06 pmThat sounds like a reasonable target. 100% off-grid just gets very very expensive in either having enough panels to generate in every the worst weather, or enough battery to get through 3 or 4 days of the worst weather, or using a generator at 5x the cost of off-peak grid power.I'm just starting, but I anticipate at least reducing my bills by 80% or 90% next summer once I get 2.5kW of panels, which is definitely 100% worth it now I have the rest of the stuff already. And maybe adding another 3kWh of battery -- I'm not sure about that. That costs about as much as the panels, but for much less benefit -- it seems at the moment with assumed 10 year lifespan for LFP and 20 years for panels, it costs about 10x more to store 1kWh of electricity (NZ$0.10) than to generate it (NZ$0.01). Storing solar power to use at night when it's cheap anyway only has about 60% of the savings per kWh of using it at the time it's generated between 9 AM and 5 PM -- it's still a positive, but with long payback period.For me the main purpose of the battery is stretching the solar (and/or cheap night or "free hour of power") into the 7-9 AM and 5-9 PM peak periods when grid power costs 64c/kWh. Solar doesn't cover all of those times in summer, and none of the evening peak in winter.Well, in fact the main purpose of the battery is as a UPS against the too-frequent power outages here. There was a 30 minute one on Friday evening, and 40 hours in April 17-19. I have a 2kW generator to charge it in longer outages. 3kWh runs my fridge and computers and internet and some LED lighting for 16+ hours. Or that plus heat pump heating/cooling at 100% (approx ±12º C difference to outside with no sun or wind) for 2.5 hoursQuote35.52º South, just a little more south than Sydney / Canberra / Adelaide across the ditch. Similar to Gibraltar, Malta, Crete, Cyprus, Tehran in your terms, but more cloudy.I'm all electric except the gas cooktop, and the wood fire which I use instead of heat pump when it's colder than about 10º C, which is maybe 50% of nights in winter, almost never in the afternoon.I used 5000kWh in 2024, of which 1000kWh was in my free hour each day (water heating, clothes- and dishwashing, some cooking, bumping the thermostat up/down), so that's about 40% as much as you. The Pecron is letting me grab about an extra 650kWh a year (a $200 value) in that free hour.QuoteOr one more 400W solar panel.

author: indeterminate
author_rank: Regular Contributor
timestamp: July 08, 2025, 10:37:05 pm
content: Most of it is Transformer/inductor losesmeasure the temperature rise in the fets from off to idle to get an idea.