In my area it seems my options are
1. To execute some sort of agreement with the power company, which would be cost prohibitive and take years in my area.
2. To extend my purchase budget way way up and purchase ~triple the panels and battery capacity that I need, in order that I could safely go completely off-grid without worrying about running short on power.
Neither of these options yield a return on investment that would make solar worthwhile, and that is greatly disappointing to me.
Net metering was great when it was an option, and it provided a ROI of under 15 years for almost any system anywhere, most under 7 years, and DIY systems even less. Within the US the government subsidies (up to 30% federal, and more in some locales) and the rapid drop in pricing almost anywhere the ROI is under 7 years, and DIY systems approach 2 years.
But even now with terrible agreements with utility providers an ROI on any solar investment almost anywhere will still yield a 15 year ROI and that's with professionals handling everything. With DIY and utility interconnect it is easily under 7 years, and most under 5 years.
That's without batteries.
You don't provide enough specifics to indicate why the utility interconnect pushes the ROI to greater than 20 years (which is the lifetime of the solar system), but I can only assume you've done the math and are correct.
Going to the extreme other end of the scale - completely off grid - you are correct, you need about 3x solar, and on top of that a significant investment in battery capacity to accomplish that. I assume that's a problem for financial reasons.
When I faced the same issues I took the middle road, which others have already suggested, to which I'll add my process that might provide you a blueprint for moving forward:
I started off with a small amount of batteries, a smaller 48v 6kw output off grid inverter, and a pallet of solar panels (about 7kw). I installed a subpanel right next to the main panel for my house and a cheap automatic transfer switch to power the subpanel from either the utility or the solar system, preferring the solar system if it's on. Set up the solar system to feed the ATS, and started moving loads over to the subpanel.
I started with critical loads (as part of my reason for this system was power backup) and then went on to heavy daytime loads. It wasn't big enough to handle the old household AC unit, but it handled all the lighting and entertainment, fridges, freezers, dishwasher, laundry, etc. 6kW is a fair bit of power.
You can buy an entire solar system kit (minus solar mounting and wire) with a 6kw inverter, 4.8kwh battery, 6kw solar for $8,000. The battery doesn't need to be huge or carry you over nights, you just need enough battery to keep the inverter happy and avoid switching every time a cloud passes over the solar panels. My initial investment was about $4k for the inverter and panels as I had a bunch of old, used batteries I could throw at it. If I were to DIY it now from scratch I'd DIY my own battery since pre-built batteries still cost 2x as much as a DIY, and it would be $5k.
Once the system was running was able to better characterize my usage and the solar input I could expect at my location throughout the year. We made changes to how we use electricity - doing things that could be moved a day or two around such as laundry on sunny days and avoiding them on cloudy days - and we entered a peak utility program so our nights were cheaper and the payoff increased significantly.
From there we put more loads onto the subpanel, and upgraded the batteries, then the inverter. We added more panels just this year - just 1.8kw for $850 (nicer bifacial panels, which should do better in winter here in Michigan, assuming I mount them before then).
We no longer notice when power outages happen. The system switches to utility when the batteries run out, usually outside peak hours. My system is complicated by the fact that it's in an outbuilding, and that causes some issues which mean we do have to manage it somewhat, and also since I'm still using those old abused batteries so I'm only running the battery system between 10% and 80% so as to avoid runaway cells on the old packs, so we are still micromanaging it, but in a new system with the inverter close to the main panel this would all be automatic and you'd never have to think about it - though you might notice the switchover depending on the speed of your ATS.
That $8k kit could supply $2,500 of electricity at your $0.30/kwh rate every year, assuming good panel placement. It would be paid off in just over 3 years. It would not involve the 3x investment required to go completely offgrid, nor the utility interconnect agreement. Going fully DIY and finding sources of cheaper panels and batteries you could pay it off in 2 years.
So I think your original premise still stands - now is a good time to invest. With solar panel tariffs increasing, and probably battery tariffs once we have enough US battery manufacturing that they start lobbying the government for protection, I don't expect it to get much cheaper.
The one thing I will suggest, though, is getting an inverter that can be paralleled. I had to swap out my 6kw for a 12kw, and while I can attach grid tie inverters (and in fact have a 6kw grid tie already set up for that purpose, just not used at the moment - need more solar panels) not all off grid inverters will properly accept grid tie sources, so getting one that can be paralleled from the start would be better.
diysolarforum.com
