Solar PV Inverters and losses.

Zardaz · 30-01-2020 11:49pm #1

Hello all,
I am currently considering installing some solar PV, but am still at the research stage and doing the cost/benefit analysis.

My latest concern is the self-consumption of the inverter itself.

I watched a you tube video this evening, from a German guy that has a small PV system.
He is using a Alpha ESS SMILE B3, which has 3KW incerter and a 2.75KWh battery.
His daily consumption is only about 7KWh, with low overnight usage, and this system can, in theory supply most of his power.

However, the Unit has a self-consumption of ~100W, which adds up to over 2.4 units a day,or 875 units per year.

If a similar parasitic drain is present in all inverters, then this could mean that nearly a full KWp of any solar installation would be spent on just keeping the inverter running. (under the assumption that 1KWp ~= 1000 KWh annually in Ireland), which would hit the payback pretty severely.

Perhaps it only applies to hybrid inverters with batteries attached, that need to run all the time? (as opposed to simpler inverters that only "come alive" when there's enough DC panel voltage).

Or perhaps it's just the ESS smile systems?

Does anyone on here have any insights or data on this?

Link to video: https://www.youtube.com/watch?v=-CDIzkmY2Fc

unkel · 31-01-2020 8:35pm

Zardaz wrote: »

If a similar parasitic drain is present in all inverters

I doubt it. 100W continuous is an insane drain. Fair enough if it is a hybrid inverter that keeps the battery warm when temps are below zero (the Tesla Powerwall has a big parasitic drain because of this), and I can imagine fans kicking in if you live in a hot area and the inverter is working near max capacity during the day

But I can't see a typical conventional inverter in a mild country like Ireland (like say a very common modern one like my own, a Solis 3.6kW dual string MPPT) use more than a few hundred Wh in a day (and not the 2400Wh in your example)

unkel · 31-01-2020 8:38pm

Just looked up the spec sheet of my inverter and it doesn't say anything about (max) self consumption during the day, but it does state self consumption at night as <1W

garo · 05-02-2020 10:38pm

My inverter goes to sleep at night and wakes up periodically to check if anything is coming from the strings and then goes back to sleep. I expect consumption during night is ~1W as mentioned.

Solar PV Inverters and losses.

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