At what point? From the start, with your architect.

You really just need to know what system size you want--you can estimate this without a PG&E bill if you know the size of the house and what types of appliances you're putting in. There are many calculators online. Under the current PG&E net metering policy you will also want/need a battery and should strive to just cover your usage with the battery in the mix. If your builder has a solar company they regularly work with, that's a good place to start--most new construction is required to have solar so they may well have existing relationships. If not, you can get quotes from other local installers. We just put a system in this summer in your area, so feel free to PM me for names. (And yes, your architect needs to know you plan for solar panels to be sure your roof can sustain that weight--but most can with no issues. You may also want to prioritize one roof design over another if you know panels will be going on some sections. Do you want to be able to see the panels from the street, for instance?)

With new, I suppose Tesla roof is an option. Not sure if it is reasonable or not but at least something to consider. The idea with their product is that it is a roof and not panels on a roof. So it is way more expensive but it does double duty as the solar and the roof.

We built new and had panels on and it really wasn't much different than having solar put on an existing house. Yes - the calculations are different. But you presumably have an energy rater who can give you estimated bills. We sized somewhat based on that.

I am in NC which has different net metering rules than CA, but we also are encouraged financially not to overgenerate. We lose all credits on May 31st or so. So a battery doesn't help.

We did not engage in roof planning just because it was one more consideration that we didn't have the bandwith for at the time.

They did do some wiring before drywall but otherwise not much else. We did 50 odd panels giving us a net HERS of -7. With EVs, we have about $500 a year in electricity costs and lose about $50 in credits from relatively high generation each May. We generated 17 Mwh and used 13 Mwh last year. We would have had slightly better payback with a smaller system because of less lost credits and a maxed out utility credit. But then each extra panel was cheaper. My point is that there is no right size that all will agree on. Sometimes you are roof limited and other times you want the fastest payback and other times you want more generation even if it is a slightly longer payback.

I'd make sure I had a generous expanse of south facing roof. Houses that have panels strewn all over the roof in all directions are inefficient, just sell more panels for the supplier and will make reroofing expensive. You want to have wiring runs and panel locations pinned down, to save cost and keep exposed conduit/wiring to a minimum.

I'm concerned that your architect is not able to guide you through this process. Do they have much experience with designing for solar? If not, I would consider bringing a consultant on board who does. You can crowd source info here, and there are some very educated comments below. But this is a big and important part of your home design and you need to get all of the details right.

This is not a crowd source question many things are involved and I agree your architect is the one driving this bus.

California:

The permitted set of plans for your home will include energy calculations that will determine the minimum KW required. This must be installed to get a CofO. Maximums may be limited by local ordinance and/or utility company.

Builders typically include systems at the specified KW using their solar subcontracto or an allowance that may allow you to contract outside .... but do check with your builder if its already a part of their contract & included in the construction loan.

If there is a construction loan, it will be difficult to add a financed system prior to CofO.

Solar is not part of our contract

This is the south elevation. There is no shade or trees on this side of the house. We have a lot of space here. I am trying to reach out to Solar companies for advice.

Thanks

Can you add solar into your contract with your architect? Does your architect know that you want solar? Does your architect have someone they know of who does solar who they can bring on to advise in collaboration? This needs to be part of the design process from the beginning.

Since solar is s requirement, planning for it should come under the architect’s umbrella. Same as the foundation plan, and integrated into the roof plan. It also impacts the size needed for your utility room and support services.

That is a terrific roof design for solar if this is south-facing. You'd likely want the primary array on the portion in the center, and can place the panels directly next to the electric meter with minimal need to do any crazy routing. (I'm guessing this is either the back or side of the house?) Whether you can fit enough panels there for your needs will depend on the dimensions (code requires fire setbacks so you lose some of that area to those, too) but you have secondary roof areas to go to if needed. You'll want to be mindful of where they will be placed when planning your landscaping, too. I can't tell from the drawing, but are the little boxes the various vents? Even relatively small vents can shade panels, so if you can design areas for panels away from vents/chimneys, that's ideal. Your architect should be familiar with how to design the roof structurally to ensure it meets the requirements to support that weight given that all new construction must have solar, but bring in a structural engineer if they aren't.

I find it hard to believe that any new roof would not be structurally sound for solar. If I could walk on a roof, I would think it could support solar - although I do realize that a big collection of panels would have some weight to it.

Solar is taken into consideration on any remodel and or new construction the additional weight for each solar panel array is in the neighborhood of 2-4 lbs per sq ft so this is to be considered during structural engineering. a standard array size is all based on size and demand normally a 12kw system is enough to run most homes less that 4000 sq ft try consulting a solar company like Sunrtrek Solar they are based in southern California but its worth a shot.

Your minimum will be specified in the required energy calcs, most likely under 4KW. Beyond the minimum may be a challenge to recover adequated rate reimbursements due to CA utilities manipulating payout rates.

The architect likely was already required to identify space on the roof by the building department & trusses should also support. Verify.

Compare lump sum costs before financing.

Besides the integrated solar of a Tesla roof you have other integrated options. Google used SunStyle Dragon Scales on their recent construction. Homeowner’s Guide to Solar Panels (2023) | Palmetto

Solar Roof Shingles, Residential Solar Roofs | SunStyle

PV Magazine has more option info. Canadian BIPV module supplier unveils two solar tiles – pv magazine International (pv-magazine.com)