No, I Don't Wash Plastic Bags

My Means are pretty generous, but I’ve still got a touch of skinflint in me. Yesterday I was already over that way so I stopped in at Walmart during the chaos of a Sunday afternoon to pick up a dozen of something for $1.48 each, saving $2.27 over ordering from Amazon.

My new (last Friday) solar electric system can’t push power back to the grid yet, so once the battery backup hits 100% the solar system only produces what I’m using instead of what it can. So running laundry and charging the car are two of the things I’ve been running while the sun shines to put that bit of extra capacity to use.

The app that controls things is pretty cool. I now see how much power I am using in (more or less) real time. I also see that my house never consumes less than 400 watts, and may hit 600 or 700 watts even when nothing extra is running. There are a few things, like my computer, that may be making up a larger part of that. I suspect the rest is all the instant-on devices. Anything that turns on with a remote has a draw. Anything with a little glowing light showing it has power. Anything with a wall wart. The stove and microwave are off, but powered up and react to touching their controls. Stereo, TV/cable box/receiver/DVD player/ROKU, router/switches/MESH, laser printer, scanner… for the first time I see what this is costing. Which, now that I have solar, will generally be nothing. Well, not exactly, but once my excess gets sold back to the grid there will be a few cents involved.

Besides the background level, I also see the peaks. The peak as the hot water heater recovers from my long, hot shower. The peak as I charge the car, of course. And run the dryer. I haven’t used the stove yet, but the microwave on high shows quite clearly. (Hopefully once the excess is going to the grid, and returning a few cents, and the novelty wears off, I’ll be less obsessed with tracking it all.)

The battery backup - two Tesla Powerwalls - gives me a bit over 20 kWh of available storage, avoiding taking them down below 20% as instructed. In the event of a long (multiple days) outage, how well that serves me depends on the sun. With clear skies, even in the winter, it looks like I would have to take only minimal conservation steps to be fine indefinitely. But on the rainy Saturday afternoon the solar produced nothing, so I might need to take serious steps to keep going when the weather is against me. At my last house I handled outages (including a three day stretch) with a small generator to keep the refrigerator, freezer, furnace and well pump working. I don’t have that generator now, but I should not need it.


I am interested in how you set it up (self, or contracted?), what devices you use to manage the power for the house, and, well, all of it really.

I have about 2400w of panels up, no grid tie, and they are severely underused, but I can’t find anyone interested in helping design a non-tied system for use around here. (Tenn a crappy state because of legislature animosity).

Any more explanation - or references would be appreciated. (Normally I’d just send this as a personal message but, well, you know.)


My system is from Tesla. 32 panels totaling something like 11kW. Two powerwalls totaling maybe 20kWh. It is all managed by the Tesla app, the same app I use for my car. A very integrated system.

Right now the one thing I can control is how low the batteries will drain. When I can finally send the excess to the grid I will set the batteries higher, but for now I have it set to 35%. Since it was turned on late Friday morning, the house has consumed 74.4 kWh, of which 12.6 kWh came from the grid.

The home screen of the app shows the current status, and a graph of the day (unless week, month or year is selected). There is an animation, moving green for the direction of flow of power.

The numbers for the four end points - Grid, Home, Powerwall, Solar - can be tapped to open a more detailed view of that number. When I opened Home, the graph showed that I was on battery overnight, then on solar during the day. It also shows my total consumption so far that day (6.0kWh) and the peak (4.7kW).

Opening up the Powerwall, the graph shows it being drained and charged. The yellow when charging means it was charging from solar, not the grid.

Since the system has been pretty much self sufficient today the page for the Grid doesn’t have much to show.

There is also a big picture screen, showing the overall impact. Of course it doesn’t have much to show yet.

For the moment I am running the way you are, off the grid. The difference is that I have the Powerwalls. These have let me run essentially without grid power since the sun came up on Sunday. If you want to get more - perhaps a lot more - from your severely underused system, look at battery backup. I don’t know the current cost or availability of Powerwalls for existing non-Tesla solar systems (though their use is not limited to solar, they could be used as a giant UPS). I suspect it changes. One article that goes into it:


I now have ten days (minus about four hours) of solar operation. The Tesla app has a page called Impact. It shows that over those ten days 14% of my power came from the grid. That may excite me, but since I’m not using all that much power it shouldn’t be of much interest to anyone else. If I used more it would ALL be added to that number.

On the other hand, the breakdown of the other 86% goes directly to the impact of having the two Powerwalls. The 86% breaks down into 39% coming directly from solar, 47% coming from the Powerwalls. Since I can not currently sell back to the grid, that 47% would not have been there, it would have just been unusable excess, if it couldn’t be stored. Which ties back to Goofyhoofy’s statement about having an oversized system that doesn’t feed the grid. Batteries make a major difference!

(About the Powerwalls… Each is rated at storing 13.5kWh, so 27kWh total. I’ve have had the system set to not draw down below 35%, so I’ve been using up to 17.5 kWh of that capacity.)