24kW per day
744 kW per month
9,000 kW a year
19 months ago, my SoCal coastal usage had moved up from a typical monthly 400kWh/mo to closer to 600 with additional of PHEV
However, after 25+ years with any Air Conditioning, the plan was to install solar and immediately install a heat pump central HVAC (for upstairs system/zone... skipped replacing gas heater downstairs as that space RARELY gets hot enough to need A/C, especially with a slightly oversized upstairs unit and warm air rising... 1.5 yrs later, happy with choice).
As I was able to get onto NEM2 (3 hadn't been formalized at time I signed contract), I skipped getting battery system for now. And I knew that within 20 year NEM2 tariff agreement, that at least 1 of our ICE vehicles (if not all) would likely get replaced by EV. So I intentionally sized my system for expected future loads (knowing small limit to expand but stay on NEM2)... Solar companies asked to confirm why I wanted 2X number of panels they proposed, but there was no issue getting system permitted/approved by local PoCo?? I went with 19x425W panels which was listed on my contract as a 8.08kW (solar energy) system but Net Metering Permission to Operate lists 7.392 kW electricity generation system (Max output VA/panel after micro-inverter being 384 [not 425 marketing number]). I am currently a net generator every month (even winter) (which SDG&E can NOT accurately bill, as acknowledged by their own CSRs, but other issue). On NEM2, the NBC are annoying but WAY cheaper than getting a battery system. Your calculation on NEM3 will be different
I mention the above context to mentally consider
- What my system (intentionally) skipped was the hybrid inverter (and associated grid-tied) electrical work I'll need when I get around to adding a battery. At this point, grid-down isn't a worry in my area (really rare, and UPS for all computers and network gear, so it takes an extended outage for any of us to care). But that is a NEM2 specific consideration
- the small investments over time (vs full system purchase and install, benefit over time) approach most likely means sticking with grid-tied to start (and simply reducing kW usage with PV...)... ie, what I have.. .much less involved wiring in/around main load center associated with a grid-forming inverter
- But as you are talking NEM3 and family indifferent to TOU rates, your bigger ROI will come from battery (10kWh won't be enough, but would probably cover peak rate usage (4-9p) and something like 14.3kWh coving much of the night??.. presuming not running A/C all night... depends on how close to the coast you are)
I can download from PoCo my usage in 15-min increments for years. From that you can determine peak and average usage for 4p->9(or10)am if you wanted to avoid a large portion of grid consumption. As others have said, getting a battery to cover 80+ percent of your typical usage isn't that hard or expensive.. It can get real costly to cover that last percentage (short sunlight winter days, storms, etc)
- the issue with NEM3 is there will be a significant limit on system sizing (PV # / output) without getting re-tariffed (sorta non-issue if nothing after NEM3, but at some point adding panels will move you into next tariff plan. For similar reason, I over-paneled to start, but that does take the up-front investment. Your issue will be if you don't have a battery to capture excess, your benefit will be limited.
- the risk you have is buying, say, half the panels now and hoping the rules don't change by the time you are ready to add more PV panels
- Now there are battery systems that work only when grid-is up. The batteries themselves aren't 'cheaper' but you do avoid grid-forming hybrid inverter expense. And you can re-wire later.... though to minimize cost, I'd wire once as though there was a hybrid inverter (with enough spare cable loop length) such that you don't have to do significant re-wiring later... but I could see arguing either way
- The costly and beneficial product purchase/install will be the grid-forming hybrid inverter, and then the question becomes sizing
- You can get your max kW draw now (most likely from PoCo). And then consider any likely planned additional near-term peak kW loads to support with a hybrid inverter (as in 5-10 yr timeframe). I've seen reference by some knowledgeable industry folks to not expect hybrid inverters to last as long as say an oven or your roof. So, wiring up front to include an inverter bypass seems prudent (those 3 generations will get quite testy if power is down for days (or much longer) due to inverter failure at some point)
The Emporia Vue has been mentioned already, and would be a great place to start, to collect more detailed (and some circuit specific) usage metrics
One other thought on decision process.... how are you (and the family) on handling grid-down situation?
For some, that is important. For others, largely a non-issue. Adding a grid-forming inverter adds a material amount to the system cost. DIY type solutions cost one thing (see comments about end-user frustrations, firmware faults, etc), and more mature (reliable) solutions costs even more. You can skip (or postpone) that cost, even with a battery, recognizing that if the grid goes down in the middle of the day, and you don't have grid-forming inverter, then power out at house (even if you have plenty of battery juice and/or PV)
if your grid fairly reliable, and grid-down situations not a excess drama creating situation (no powered medical devices, etc), then doing grid-tied solar and battery now (my recommendation to wiring assuming future hybrid inverter install to make that much less involved when the time comes)
With limited budget, the question of how many PV panels to get when, and battery gets tricky.
And be aware of how non-certified setups might impact homeowners insurance (not saying don't do go that route, just be eyes open about it).
Your challenge is that there is a certain up-front cost for systems capable of your expanded system capacity (ie battery system that could cover whole house or critical loads [assuming plan to re-wire to enable such] while starting small) vs expense of replacing (expensive) components as you outgrow early installations .. and issues with permitting etc for a grid-tied system