Too Much of a Good Thing?

[jimbo435]

We are designing an all electric home in Northern California, Lat 38.72.
I was thinking of putting solar (PV) on half the house (1000sf of solar), half the garage (400sf), and perhaps even some tracking arrays in the field.
While we will be grid tied, I want to make sure I can go at least a week without power, and ideally much longer.
I figure I can sell back to the grid any excess I have.

Questions:
1) What are the downsides (other than cost) to having excess solar capacity?
2) What happens if my batteries are full, and the grid is down?
3) Panels will face due south, but roof pitch is 3:12, or 14 deg. How much efficiency will I lose in winter with such a low angle?
4) Typically, where would I find professionals to design such a system?

Thanks

[SunEagle]

Hello jimbo435 and welcome to Solar Panel Talk.

I believe you are talking about a hybrid grid tie system. That usually contains an inverter that will connect both to the grid when it is working or charge a battery system when the grid goes down.

[J.P.M.]

Get a copy of "Solar Power Your Home for Dummies". Either ~ $20 at bookstores/Amazon or a slightly dated version online as a free PDF.

Read the book and review your questions. Pay particualr attention to the parts dealing with load reduction via conservation and tolerable/relistic lifestyle agjustments.

On # 4, avoid the big national outfits. Local outfits that are licensed and established electrical contractors who also sell/install PV are your best chance of getting most bang for your buck.

FWIW, battery storage is not quite cost effective yet. Also, lots of hype/pie in the sky stuff from peddlers.You're probably using 30-40 kWh/day. Common battery in homes will meet are about 1/3 of that load and are expensive. Read up and at least walk in with your eyes open and your brain informed. Reality will take hold at some point.

In the meantime, reducing your usage will be the quickest and most cost effective method to reduce your electric bill.

[donkey07]

It sounds like you are looking into a hybrid system, The inverters for the PV panels will determine where the energy is allocated ie. back to the grid, charge the battery or run your appliances. They are set to run the load requirements of your house first and charge the battery with the excess and when the battery is full they switch over to exporting the grid. If the grid power goes down during non or low daylight hours the battery should take over the load seamlessly, however, in daylight the house should run on the PV panels. There is no real issue having more panels as they are generally one of the cheaper components of your system. In regard to your panels angles, The installer can use framework on your roof to create a greater angle so you should be able to get the efficency you need.
I just installed a full off grid system (no grid tie) with 8.5kw of tier 1 PV panels (aprox 32) 2 inverters and a 13.5kw battery and have found no issues running a 4 bed house. As for installers in CA im not sure as i'm in Australia.

Hope some of that makes sense.