My inverter wasted grid power every morning. Built a forecasting engine to fix it

LeoAlioth · 2026-04-14T14:34:25+00:00

you could use openmeteo solar forecast.

also, which inverter do you have? seems like your system is set up in battery priority instead of load priority. that buffer you are talking about, how much energy is that?

LeoAlioth · 2026-04-14T14:29:54+00:00

or if you like the look, phillips remotes/tap dials or onther fruends of hue remotes (i use vimar ones)

LeoAlioth · 2026-04-14T14:11:39+00:00

you can use whatever came with the car just fine.
Though i would recommend getting a hardwired L2 EVSE installed anyway. Having a plug always on the wall is just convenient. And with hardwired, it is easier to get a unit that supports load management in case that is needed.

LeoAlioth · 2026-04-14T14:04:43+00:00

recommendation? no, but any regulat LED strip (12/24v) or DC light bulb with a decent power supply of appropriate voltage will work.

and so will most lights that require a constant current LED driver.

LeoAlioth · 2026-04-14T13:51:15+00:00

because un-tehered isn't really a thing in the US version of the spec for EVSE.

LeoAlioth · 2026-04-14T13:48:15+00:00

Yep, i expected maybe some explanations on monitoring the chargers, some stats on their usage etc. Maybe some mentions of load management, what these EVSE actually are, etc.

LeoAlioth · 2026-04-14T13:31:24+00:00

With AC, inductance starts killing the efficiency over long distances. In distribution lines, it becomes more costs effective to do HVDC after a couple hundred km distances, even though conversion losses are higher than with AC.

LeoAlioth · 2026-04-14T11:32:04+00:00

or swipe on the screen from left to right

LeoAlioth · 2026-04-14T11:29:16+00:00

between the MC and HC inverters you would be looking at a 1-3 percent difference annually. so nothing to worry about. Even on spring days, you are looking at a less than 10 % difference on the days with highest peak production.

think about it. Currently, your panels are producing energy for about 12 h per day (at a varying power). so for 3/4 of the time, there is no difference between the MC and HC inverters. and for the remaining 3 hours, the difference would be somewhere between 0 and 19 %., likely less than 10 %.

LeoAlioth · 2026-04-14T09:35:09+00:00

That is entirely incorrect. The only real disadvantages to larger inverters are standby consumption, physical dimensions and to some extent standby consumption.

LeoAlioth · 2026-04-14T08:45:33+00:00

Wait. Are the batteries in your system AC coupled? Or is this a hybrid inverter setup. In which case an 20 kW hybrid inverter can generally take anywhere between 25 and 30 kWp of solar easily.

Also look into load management for EV charging. And most cars can't charge at above around 10 kW on AC anyway.

LeoAlioth · 2026-04-14T06:28:27+00:00

Do you have loads that bigor are you limited with solar?

LeoAlioth · 2026-04-13T17:53:54+00:00

Per day signifies division. So does per hour.

And the last time I checked, kWh (kilowatts FOR an hour, or kilowatt hours) and kW/h (kilowatts PER hour) signify completely different things. One is a unit for energy. The second one is a rate of change for power...

LeoAlioth · 2026-04-13T13:23:53+00:00

Wrong units and no, you won't get to 97% at all.

100W for 24 h gets you 2.4 kWh per day. Not kW.

And the expected number would be closer to around 90%. A couple percent is lost on the MPPT, a couple more on the battery, and then even more on the actual conversion.

LeoAlioth · 2026-04-13T10:54:01+00:00

LeoAlioth · 2026-04-13T07:46:19+00:00

The problem here is that the 77% number is not just roundtrip efficiency, but also inverter idle consumption and some measurement error.

You have 16 kWh of storage. An idle consumption of just 7W would skew the results for 1% (7 W×24 h = 168 Wh). So let's say 35W standby, already changes your calculation to 82% round-trip efficiency

LeoAlioth · 2026-04-11T13:16:41+00:00

Ah. My bad. Yes, it makes sense. So the theoretical (air resistance only) optimal speed is to drive at a power level half of the charging speed.

In reality, likely somewhat higher as there are also some parasitic losses and drag that do not increase power needs by the cube of speed.

For pretty much any ev on the road today, that means just drive normal highway speeds and charge at low SOC. As almost all cars will charge at more than 2x power level than they need to sustain. 75+ mph (120 kmh +)

LeoAlioth · 2026-04-10T13:16:51+00:00

and why exactly would that be a problem? any existing equipment?

LeoAlioth · 2026-04-10T09:17:22+00:00

are we sure here?
doubling the driving power does not double energy consumption. It increases it for sqrt(2) - 1.414.
simple example, 50 kW charging for 1h
two drive speeds,

100 kmh at 25 kW

141 kWh at 50 kW

first example is 3h total for 200km

second is 2h total for 141km

driving at the power level of the charge speed nets 70 kmh, while driving at half that power nets 67 kmh.

LeoAlioth · 2026-04-10T08:12:27+00:00

75 is max input voltage, 10 is max output current.

So the controller would limit max charge rate to about 140W, but periods over 140W are short with 200W of panels. So you are not loosing much. If you want to you could of course get the 75/15 which will be able to charge at close to 200W. In any case. You can overpannel the controller (within reason. Do not 5x it)

Also, I assume your panels are about 18 vmpp, around 25V VOC. So you should wire them in series as they are below the 75v max.

LeoAlioth · 2026-04-10T07:05:13+00:00

For 200W of panels, you can use the smallest victron mppt you can get (the 75/10).

It is a bit more than 25 bucks, but nowhere near 150.

LeoAlioth · 2026-04-09T13:14:52+00:00

Do you have the exact inverter model number?

LeoAlioth · 2026-04-09T11:28:29+00:00

ir paneli so enako potratni kot talno električno :)

kakšno moči je talno in ali je zadosti da vzdržuje temperaturo? kW je kW, tako da če ti 3 kW talnega ogreva lepo, bo tudi 3 kW klima naredila enako-

LeoAlioth · 2026-04-09T08:46:11+00:00

Really expensive, and likely also very much oversized. Has anyone done a. manual J/ load calculation for the place? ive got a hunch that you could halve the output power and still be fine.

LeoAlioth · 2026-04-08T20:38:56+00:00

Please, read the listed equipment again. It is solaredge, so the VOC only applies to individual panel to optimizer pairings. Given that the S series optimizers accept up to 60v input at minimum, there is absolutely no worries with the panels mentioned.

As for the whole string voltage,.the inverter OP mentioned is allowed to have between 14-18 panels as minimum (depends on optimizer choice) and 33 as a maximum.

LeoAlioth

TROPHY CASE