Help in evaluating if small solar DIY grid tie system is good choice

New member to the forum so I hope it is ok to discuss grid-tie solar projects here. Sorry if not.

Summary -

• California
• 1600 sqft home with an electrical usage of 800 to 1200 Kwh
• Gas heater, water heater, and cooking stove
• Numerous fees and taxes including a 5% local tax
• A buyback rate of about 8 cents per kWh
• June bill (excluding gas)
  • $540
  • 1050 kWh
  • That's about 51.3 cents / kWh

My home has an older tile roof. I am not currently interested in mounting panels on the roof. I do have a small shed with one of the roof planes facing south. Each plane is 5.5' x 12' and I am guessing could hold 3 panels. So 6 panels total. Additionally, I am considering a somewhat unconventional mounting of panels on the south side gable end of the house. Maybe expand with 4 - 6 panels there in the future. There is no southern solar obstruction in any of these locations.

Given the abysmal buy back rate of 8 cents per kWh and the limited number of panels I am wondering if a grid-tied system w/ battery backup and no net metering would be a feasible solution. The home would run off of batteries and charge from the grid as needed. I am hoping to get reasonable pay back by installing most of it myself and paying an electrician for as little as possible. I imagine that, since I am not feeding into the grid, I am unconstrained on what equipment I can use. Then I would be able to buy a cheaper (?) inverter that does not need to be certified by the local utility. And paired with a cheaper DIY battery. Used inverter?

Is this a bad idea? Should I just be looking at a grid tied net metered no battery solution? I am hoping to move to a new home if prices ever come back down to earth so I am thinking that just eating the costs may be better for a while. Additional utility fee hikes are already slated.

I know the best solution would be to use less electricity. We have set the thermostat to 78 in the summer and are mindful of our usage. I have a desktop that is on for 12 hours a day (work from home). I am not interested in the energy efficient washer and dryers. But maybe a new A/C would be a better use of money? The house had a energy use evaluation a few years ago and the ducts (the attic is unconditioned) do neat leak.

Thanks,
Dennis

Use PVwatts to compute how much you can generate in the summer with that small number of panels.

Then guesstimate the probability your AHJ or neighbors may take issue with the unpermitted install.

3 panels per plane is rather difficult to work with with respect to minimum solar voltage, you likely cannot use a lot of high voltage MPPTs since each plane needs to be on a separate MPPT or you need to use optimizers to compensate. You will have to get your string design vetted here

Basically .. yea bad idea... 'cuz

short version: grid-tied means net metering and all code and equipment compliance rules.

- The issue you have is that local jurisdiction will have rules on electrical system work, that avoiding creates insurance coverage and other risks
- Per discussions on this forum, sounds like PG&E is worst of CA power companies in terms of hassle getting through permitting process. permitting during rush install time of fall '22 (everyone rushing to beat NEM3 announcement/cutover) for SDG&E was only a couple of weeks. so it depend on where you are as to how onerous compliance can get
- And you could go 'off-grid' (truly physically disconnect) but that has its own complications and expenses (usually not worth it from a pure financial analysis perspective)
- Presuming you do keep grid connection (because not dong so will be really expensive to have sufficient power in winter months on cloudy days), then you are grid-tied, whether you have interconnection (export) agreement (net metering) or not. Basically if grid-tied with simultaneous self energy generation capability, then you are basically required to get an inter-connection (net metering) agreement. The exclusion is for a generator (with appropriate lockout /transfer switch) such that you are either running from generator or grid, but never both at same time.
- and with power companies incentivized to find rule breakers, and easy of access to regularly updated satellite imagery, very easy to spot new solar panels installed. At which point expect a knock on the door and a demand to either be inspected or get cut off from grid (and probably fined at same time)
now, you can install solar, and move loads over to a PV only load center, preventing even possibility of feeding back to grid... ie those circuits are NOT grid-tied. Then you could install a transfer switch to cut-over from PV/battery system to grid feed (again, an either or setup, not both.. that typically means a circuit outage for the cutover)

There are systems that claim zero-export settings option, but if you read these forums, you'll come across numerous reasons why that is not sometimes not 100% effective (and being careful won't be good enough). And getting caught backfeeding the grid from a system not permitted to do so (extremely easy to catch) could cost you a lot more than following the rules.

Just in case this helps / for reference/comparison
I'm also in CA, with fortunate coastal weather and primarily natural gas appliances as well... so my average kWh consumption, with PHEV was around 600. Solar system quotes usually were for 9-10 x ~425w panels (no battery, NEM2). I knew I was going to get air condition at same time as solar install, and wanted PV production to cover future EV and appliance electrification (due CPUC/NEM limits on system expansion in future years without being re-tariffed)... so I ended up with 19 panels.

With your usage 2X mine, that puts you around my same 19 high-efficiency panels to cover your usage.

That said, everything helps... however, in the overall scheme of the project, the actual panel costs tend to be smaller cost item (vs wiring. inverters, mounting system, etc).

I have a Spanish concrete s-tile roof (2-story house) which I had done a full lift 'n lay a few years prior (important factor)
- The rules changed in mid/late '22 in terms of panels installed on roof atop roof vents. something to be aware of
- I specifically chose a solar installer recommended by my roofer, such that he would maintain his full roof warranty
- It is not uncommon to need to re-felt between tile and wood of roof every 40 years or so. Depending on age, it may make sense to have roof lift 'n lay done and put solar panel mounting system in at same time (so whole roof, not just near worthless 'penetration' warranty
- My installer was rushed and took unethical and code violation shortcuts (own story), but 18 months later, no roof leaks... so my point is that there are really good reason to not install on the roof, but to cover that much electricity usage, you may need to? and if done properly, should be fine for life of system/roof
- if I were to do it again, when I did lift 'n lay, I'd have had roofer/plumber consolidate and re-locate roof vents, moving them away from any place I'd consider putting panels... makes things so much easier in the long run

With that said,
- the cheapest energy savings is often via reducing consumption, vs offsetting with PV production. though, it depends, don't be surprised if a better return on investment comes from upgrading, say, an old air conditioner to something using a lot less electricity (newer model, heat pump version, or ??)?
is Air Conditioning why your electricity usage so high? I don't know if I could use that many kWh/month, even if I tried
Something like the Emporia Vue can be good for identifying details on your electricity consumption
- any PV production will help.. but there will be a point of initial costs such that you are bound to want enough panels to make it worthwhile. And CA NEM rules limit system expansion without starting over