My system is running in Eco mode and it looks to be trying to balance grid power to 0 as if fluctuates between around +50W and -50W. Is there a way to adjust the balance point so it tries to balance to, say, -50W (50W export) to try to have an absolute minimum import and therefore cost for imported electricity?
dtackley No, there's no facility to offset the balance point, although this time of year, provided you have sufficient PV, I'd expect the import to be less than 1kWh/day (measured at the energy supply meter). If your inverter is an AC-coupled, then it's doing the job it's designed to do. If it's a hybrid, I'd expect it to be exporting this time of year.
dtackley Remember that the odd ups and downs are millisecond snapshots as the electronics see it, they aren't seconds long usages..
Looking at my Import / Export this morning I see similar swings to you by the sound of it. However, checking the hourly usage on the meter: 0, 0, 0, 0, 0, 1. 0, 0,1, 0, 1, 1, 0, 0, (watts) so far today with the reported daily usage as 0.00kWh
I would say that is minimum import & cost.
Tim Daytime import rate is 39.48p and I was wondering if I could prevent any import at all by balancing to a small export rather than zero.
SilverArt I usually have a net export as PV production > battery capacity + usage. What I wanted to do is see if I could completely get rid of any import (usually around 0.5 kWh per day) by balancing to a small export rather than zero.
dtackley Absolutely understand the strategy. Our import is 39.93p/kWh peak and 4.5p/kWh off-peak. Our peak consumption averages about 366kWh/year (£146) while off-peak, it's 1,806kWh (1,637kWh Nov-Feb) about £81, averaging about £35pm including standing charge.
If we were able to offset the balance point to an export of 50W, I don't think we'd actually save much at all. Every time the kettle goes on, it takes a finite time for the inverter to ramp up to meet the load and similarly when it boils. Using the batteries all year round and off-peak charging in winter are the main reasons why we have managed to reduce our energy bill so much.
Since installing PV, we bought an EV, saving about £600pa in petrol. The EV gets charged from solar whenever we can but we have to charge off-peak in winter, the balance being 70%PV and 30% off-peak, at a cost of £33 (included in the £81 above).
On a plus point, future inverter firmware is said to have much improved response times, so the kettle boiling scenario should result in lower energy import.
dtackley Balancing what? If the average system cost is 500w per day wouldn't you just add that in to your calculation? Or, do you really need it to be more accurate? I'm quite intrigued as to what you are trying to achieve.
SilverArt Import and Export are with 2 different suppliers. What I would like to see (= holy grail) are days with absolutely zero import so over the course of a month I am not using between 15 and 30 kWh of on-peak import.
Tim I'm pretty similar to you. Looking at my 30min grid data, it is the period when the battery is supplying part of the load or is charging with zero export that I would like to improve. Typically between 18:00 and 12:00 at the moment I have a small import in each time slot. By balancing to net export I think almost all of this (except for kettle spikes) could be removed.
dtackley The newer inverter firmware will help. We look at the income from SEG, which over the year just about pays for the standing charge. IMO it's the law of diminishing returns and the effort involved in reducing an acceptable electricity bill (compared to what it would have been) further isn't worth the effort. I'll take the faster response time of the new inverter firmware when it comes but I'm not expecting it to make much difference over the year. We have two hybrid inverters so our response time is effectively half what a single inverter does.
dtackley I see your logic but I don't see such a large problem. This month's bill for me was 11.9 kWh and I know a little bit of that was an abnormal peak usage that solar/batteries couldn't supply. IMHO a reasonable 'cost' considering all electric, including hot water, is covered, and I'm getting a feed in pittance to help offset that.