My first off-grid Victron install is done. I had a hard time with it... steep learning curve with Victron, especially for someone with average-at-best intelligence (like me). In the end, I think the system turned out nice. Stay tuned for a few lessons-learned blog posts.
A ground-mount photo is here.
An electrical-shed photo is here.
It's official: my little install company (Oakstead) specializes in off-grid installations. With Victron or MidNite Rosie inverters. While everyone and her mother in the "professional installation" world is gravitating to all-in-ones... I'll swim up river with component systems. Why? Well, component based is the only option with Victron and MidNite's Rosie inverter... and this equipment is arguably as rugged and reliable as it gets. Victron rocks low-frequency transformers like it's 2003. I like modular systems in general... add another PV charge controller to bring in more PV power, instead of a whole other inverter (or two).
Ideally I'll typically install this equipment in Oakland (my home town). ...Mostly at sites that have an electric-grid connection, but want to relegate it to backup emergency power source (and maybe defect altogether a year later... if AHJ approved). I want to be above board with the City, and get the systems permitted. A problem is that — while Victron and Rosie have the core UL 1741 safety listing — they don't have the UL 1741-SB grid-support listing. I don't blame them (as I wrote about here).
The off-grid system needs to be behind a (UL-listed) transfer switch. It needs to support all loads during the highest practical usage (not just "critical" loads). While the inverters can be "stacked" to support huge AC output... a wall of inverters is too expensive. To avoid this, the overall system needs to include flexible-load control. Examples: Turn off or throttle electric-car charging when necessary. | Run the house's heat pump during the daytime hours, and coast on that thermal mass in the evening.
I want to geek out with custom flexible-load control. A (highly-programmable) Victron communication hub, Shelly monitors + relays, OpenEVSE car charger(s). This approach requires a manual transfer switch, where it's assumed that the occupant is actively controlling which loads have access to off-grid power (i.e. there aren't minimum load-support requirements). (To be clear — if the system is designed right — the occupant won't in reality need to actively control loads.)
...With an automatic transfer switch, the flexible-load control assembly would need to be UL listed (i.e. more expensive and rigid, with a high-faluting brand to incorporate (e.g. Span)).
I went into the Oakland building department a few weeks ago, to find out if they'd consider permitting inverters that don't have UL 1741-SB. They were refreshingly open minded, and I left hopeful. I learned that Oakland plan checkers don't scrutinize electrical details... the inspector does this in the field. But for my weird isolated-from-grid situation, it'd be dumb to install the system first and then risk the inspector's off-handed rejection. Fortunately, Oakland offers the option to pay for a preliminary electrical review (for approval (or not) before construction starts).
Victron inverters accept and control generator input. Oakland is okay with generators in residential areas, so long as they stay under 45 decibels. ...Preferably located in the backyard versus the side yard. I want to model a system with a small (~5kw) inverter-based generator... meant to charge the battery during long stretches of overcast weather. I'm curious to see how quiet I can get it, in a sound-proofed enclosure. I'd incorporate a propane-tank sensor into the Victron hub... maybe offering the service of swapping out propane tanks as needed (~once a year?).
My next steps are to design a system, work out a plan set (hopefully with support from my plan-set provider), and submit to Oakland for review. I'll let you know how it goes.
In parallel, I need to work out an updated grid-defection financial model (without the federal tax credit). ...With the most expensive grid electricity in the continental U.S. over 20 years vs. dirt-cheap PV modules and pretty-darn-cheap LFP batteries... by golly it might be a good financial decision.
How sweet to move sites to local-government-sanctioned off-grid systems in the heart of PG&E territory without seeking PG&E approval... because it's none of their damn business.
Any related (public) thoughts are super welcome here: blog@slowpower.wtf
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Nicco R:
Very cool read Mike. I too love doing things the hard way. Look forward to hearing more next month.
Reuben L:
Everything about this post, I love.
We have been thinking about the possibility of small "on-grid / off-grid" systems. A zero-export system. However, the one element we would need to incorporate is the grid as automatic backup source. Not manual switchover.
Adam G:
I agree, I think mainstream adoption of offgrid keeps getting pulled forward more and more with NEM-3, rising electric rates + IRA repeal. Maybe in 3 to 5 years everyone is going that route?
