Inverter Efficiency Experiment

Small experiment as I knew today was going to be a good PV day. Aim was to see how the inverter coped with various loads etc whilst the inverter combined with PV was capable of supporting all house hold load without having to draw from the grid.

Started at 0900 and according to my smart meter I'd imported 7.47kwh at that point, finished at 1430 at 7.59kwh as my last cup of coffee pulled 100w of grid support (tracking demand on the Myenergi app).

So worst case that's 140wh over that 5 and a half hours due to inverter lag or 3.37p at 24.14p per unit.

Few points to note, I've done 3 loads of washing with demand for heating the water at around 3kw, various cups of coffee, microwave for soup for lunch, 5kwh of grid export, 2.4kwh into the Eddi, 2.2kwh in the Zappi which has had at least 10 interrupt cycles now due to transient loads plus TV on and off, central heating boiler and pump cycles etc.

Given those high transient loads I think 140wh is pretty good, the washing machine has pretty much been on constantly over the period, shame the EV wasn't about when it was sunnier and I didn't export that 5kwh to the grid!

Worth also noting the due to having to cycle the Zappi it went through a charge ramp up check which pulled 800w from the grid briefly. Faff with frequent disconnects causes my car to lock out the charge after 5 reconnects as it sees it as a dodgy charger.

On the subject of efficiency. Do folks have an opinion on whether it is better to use the battery power to power a steady low level of demand (say through the night) or a heavier and fluctuating demand at other times. This is for situations where solar power charges the battery some, but not enough to power everything until the next wave of solar comes through hopefully the following day.
Clearly if there is sufficent solar to use the battery constantly then it's not a problem.
I don't have Octopus go or equivalent so it only makes sense to charge the battery from the solar and not from the grid.

kwmc I would just leave it on Eco and let it run til empty and grab whatever spare solar it can. If possible moving some of your usage to periods when the sun is out will help even more. But setting Eco and leaving it will be your best bet.

yandards So worst case that's 140wh over that 5 and a half hours due to inverter lag or 3.37p at 24.14p per unit.

That is very good information, I will have to try the same thing when we have our next good solar day.

Just as a note, my system was installed in Dec 2020 and I think, that at some point in that time, the balancing of changing demand has changed from using import as the balancing factor to using export. If I recall correctly the import graph used to have a lot more changes than now, and the export a lot less. When I check mine, I will log both the import and export.

I have to say that export is the best balancing factor on high solar generation days, but import would be better on low solar days. Perhaps that is something that Winter Mode could do?