Image is a graph from the electric company showing my usage for a day this week. From 6:30 AM to 8:30 PM we used absolutely no utility power.
I’m almost at the three week mark for having this system up and running. The first two weeks I only had 3 KW of PV input but I added another 5 panels to bring it up to 4 KW last week. It’s also still running from a transfer switch in “off grid” mode because I don’t yet have the prep work done to move my breaker box and start moving circuits to it. (That means I’m either on full solar+battery or utility, no mixing or load sharing).
Once I get it wired in fully, I’m probably going to switch to time-of-use billing. Unfortunately, I can’t do that ahead of time because rather than just making off-peak use cheaper, it makes peak usage (M-F 7am to 9pm) extremely expensive while off peak dirt cheap. I wish there was a middle option, but it is what it is.
I’m also being very conservative with my battery usage since I want to have at least 50% in “reserve” to cover power outages. That’s especially important during these heat waves. We could easily run 24/7 but would have to take a day off every so often to just let it charge back up since my system is a bit too small to cover all our usage indefinitely (at least if we want to run the A/C for comfort, that is).
Where I live it’s legally required to tell the power company you are using solar, so you might want to check if you aren’t obligated to do so.
Already checked, and we only have to involve the power company if any of the following:
- Feeding any power back into the utility grid (i.e. grid-tied / micro-inverter / “balcony solar”)
- Using a “make before break” transfer switch that, no matter how brief, briefly couples locally generated power to the utility provider’s grid.
- If the project requires disconnecting the meter or shutting off power upstream of our main disconnect switch
As is, this system doesn’t touch the grid at all since it’s using a “break-before-make” transfer switch from an old Generac system - it completely disconnects the utility input before connecting the generator/PV’s output into the home wiring. I’m also fine once I have it fully installed because it cannot feed power out of the utility input connection, so it remains isolated (unless I would just happen to hook it up backwards which would be a whole other set of problems lol).
I’m curious how you are doing this without losing power momentarily on switchover? Are you always drawing from the battery, and then just changing charging source from grid to solar? Or do you have two stages of switching so you can use the battery as a quick-throw buffer before you detch from the grid?
We do lose power during the switchover. Same as if a backup generator were kicking in (a backup generator is pretty analogous to how I have this wired up currently)
My WFH office, homelab servers, 3D printer, and the fridge are all on UPSs. Fridge is a long story, but a UPS has proven beneficial to deal with its Samsung-ness. Everything else doesn’t really care since it’s only a literal split second to make the switch.
The only drawback to this manual switchover is the oven and microwave clocks are never right. But to be honest, even before we started switching over to solar every day, the power would flash almost as soon as we set them so we largely just ignore them. Side effect now is they’re both timers showing how long we’ve been on solar that day.
Once I get it installed fully, there will be no cutover. It acts as an on-line UPS, essentially, and the only thing that changes is where the inverter is drawing it’s power (PV, battery, utility, or a combo of any of those). It also, supposedly, has a 10ms switchover time if it has to go into “bypass” mode to feed the load directly from utility input. 10ms is comparable if not the same as the switchover time on my other UPSs.
Good to know you checked! Excellent job!
Overnight in the darker months, you could use a huge battery to change your power draw to overnight while charging for use in the daytime.
Can i ask what you’re using to monitor your usage? Is it something installed in the panel to detect wattage?
The graph displayed is from the power company website. It’s showing the power I use from them (uploaded from the smart meter). The relevant bit there is the negative space where I’m not using any utility power.
For local monitoring of the PV system, I don’t have anything yet except for the counters displayed on its LCD (see below).
The inverter has a smartphone app and wifi-module but that requires creating an account and letting it upload stats to a 3rd party server which I will never allow. However, it also has a serial port and speaks the Modbus protocol, and it’s pretty well documented.
There’s a HomeAssistant plugin (ha-solarman) that I’m going to setup when I have time. That’ll pipe the inverter stats to a HA dashboard and can also let me change some of the config options from there instead of having to go to the inverter’s panel and set individual parameters.
Sorry it’s blurry, but had to snap it quick since the display runs in kind of a carousel between different values. It’s showing here that I’m getting 2.3 KW from PV right now, one phase of the output is 0.1 KW (the other is 0.9 KW; it displays them separately), the battery is at 53.6 volts and is being charged, and I’ve generated 267.3 KWh since I installed it. The utility input is disconnected so there’s no arrows coming from it.
Thanks very much for the detailed info. It seems Europe is much more friendly about providing info to the customer. The US allows our power cos to keep a lot of the data under wraps. Solarman looks like a great set of products but is sadly eu-centric.
I’m in the US, lol, just not in a very solar-friendly area. The power company data I have access to is a side effect of both their green washing and constantly rising rates. It’s supposed to help you manage your bill more than anything else.
The batteries and inverter I’m using are Eco-Worthy which is Chinese and available globally. The inverter itself is a re-badged SRNE and has proven to be reliable and well built. Not sure if they’ve passed EU certification, but they’re UL9540 and UL1973 certified in the US
The HomeAssistant module was made for Solarman products but is compatible with others such as the inverter I have (which is itself a re-badged SRNE one).
How big is your battery? Are you using LiFePO4?
I’ve got two 16 KWh LiFePO4 batteries (314 AH @ 53v) for a total of 32 KWh.
Wow, that’s rather massive!
Have you considered bringing an EV with V2H function into the mix?Planning on getting an EV eventually but haven’t explored V2H. Could possibly use it as a second level backup or use it as the reserve and use my house batteries fully rather than treating them as empty when they hit 50% (saving the bottom half of them for emergencies).
But yeah, having an EV is still a good ways off (2-3 years minimum) so haven’t thought too much about it. AFAIK, nothing about my setup “paints me into a corner” such that I wouldn’t be able to use that functionality.
Your setup sounds great for including V2H, which would add another big amount of kWh to your electric energy storage - depending on the EV and its battery.
Take into consideration that not all EVs support V2H, but that might change a bit within the next few years.
