So you would sell at 28.7 and buy back at 3.3+tdu?(Don't forget to add 20% to the purchase cost for conversion losses)
So in the summer let's say 7pm to 10pm how much will you be able to sell? If you subtract house loads and ac loads how much of the 12kw is left to sell back to the grid?
Good question. I've taken my past two years of smart meter readings and loaded them into a database. Then I use excel and some simple sql queries to get my avg usage/month/hour so I have a starting point of my energy needs throughout the day. Once I have that I can start running scenarios for each power plan. I've used the published numbers from EG4 for conversion losses (95% battery charging efficiency, 94% battery to grid) but even at 20% loss the numbers are still acceptable to me. I also assume discharging to 3% using a pseudo Will Prowse methodology.
For sellback, in the morning i would run off battery during the peak time and can sell all 3 hours (6-9am). In the evening I would wait until the 9-10pm hour to sell back. On average throughout the year I would have about 9.7kwh in reserve to sell back (~$2.66/day during this time).
In summer time I would run out of battery in the last hour in June, July, August but that's where the rollover credits should come in. I would also be close or negative in whatever month we have a freeze since my pool will be running 24/7 for freeze protection. And these times can also be variable if I change it the EG4 settings manually each month or do a HomeAssistant integration to automate it.
If you don't export, but simply self consume during peak hours and charge during off peak hours much are you saving and does it offset your equipment cost?
If I only do consumption in a TOU free nights plan then, with only 3 batteries I would have be dynamic month to month and shift my battery usage start time depending on the season and when I use the most power (mornings in winter, evenings in summer). If I go for two more batteries then I could, practically, run all day and be under the 80kwh limit for residential households. Payback for this scenario would be <5 - 7 years depending on the number of batteries so still within the warranty of 10 years. I've looked at plans that are 9p-7a free, 8p-6a free, and 9p-9a free and the best ROI comes from 8p-6a because of the way I use power. You would think 9p-9a but on peak prices for that are $0.35/kwh which kills the ROI.
I know reducing my overall usage would probably be the cheapest route but I really don't see that happening. My house was built in 2022, I work from home, my wife is a homemaker, and I have 2.5yo, 1.5yo, and 2mo children who are only gonna consume more power as they get older.
