Comment by yesdocs

This exactly. We run a 100KW microgrid on Hispaniola, and most of our panels are oriented to maximise winter afternoon sun, or just pointed randomly at the sky. Random pointing gets us more power than all oriented 12 degrees south because the power we care about is in overcast conditions, especially high altitude overcast, and that is variable in intensity in different sky regions on a minute by minute basis.

Also 12 degrees south would put a mountain partially in view of the panels, and mountains don’t provide much light here. (I don’t mean the mountains would block the sun, just a band of otherwise visible sky)

When we do have high intensity light, the late afternoon is when we want it, and also when the sun is most off to one side of the sky.

My advice: over panel as much as you can. We can fully charge our batteries while running the farm and 6houses in three hours of full sunlight, so we still get plenty on overcast days, and even on the few darkest days we make about 70%. We have to supplement the solar about 60 days a year total, burning a total of 300 gallons of fuel over the year for a small farm and 6 houses.

The Powerwall system prioritizes filling up the batteries first. I assume it will take pretty much your entire solar day to fill your three batteries so why didn’t you choose the model that fills up your buckets as the first priority? I think the rule is “optimize on hourly storage” and the hourly production should follow that requirement. Doesn’t the 74% give you a bigger area under the production curve than the 72%?

We have a small roof with 1/3 of our panels facing east, 1/3 facing west, and 1/3 facing south. Given a sufficiently large roof, it would theoretically make sense to have all of the panels facing south.

However, due to the fact that PG&E keeps shifting our peak hours, we actually get more credit for producing in the afternoon, so when we expand our house, I'm planning on having all the panels (as much as possible) on the west-facing roof.

Also, we plan to install air conditioning at that time, so it will be helpful to be able to handle that peak demand.

There is no 1$ in electric production, unless you are selling and buying simultaneous at the exact same date and time, and from the same location. A fair price would be the current market price at the point in time, subtracted with the cost of operate transmission, facilitating the sale, and the predicted reduction in market price by increased supply. Depending on where you live the price difference between the average day of selling and average day of buying may very well be quite different. It is not uncommon in Europe to see negative market prices, where overproduction is not going to benefit the electric company at all.

> and I am surrounded by very tall trees.

https://www.suncalc.org works great for shade calculations, I was surprised when I checked tree shadows for different times a year.

Man your comment rings home so badly. Made a similar jump last year, and I was surprised we outperformed the predictions. Living in a cursed area (rainy + cloudy all the time), more than 50% of the year our electricity is 100% covered by our solar panel. 0 transportation (which is very high too).

It’s $0.08 for every $1 at retail rates, from the powerwalls, regardless of time or market prices?

Thank you for the example. I am always interested in real-life stories from other snow-laden users.

What do you use for heat?

Mostly agree, but there are also variables like feed in tariff (or delta between export and import) and mine just changed to 2 cents NZD. I've switched off hot water, battery and car charging scheduler because there is no point to save this anymore.

Plus modeling goes only so far when your behaviors change. I found it's incredibly hard to model this when there's so many variables.

Can your system work during a power outage? Most US installed ones up until about 5-10 years ago could not because they lack a proper automatic transfer switch certified to never back feed.