Solar Power - Installation Day 2

More mounting hardware is now on the roof, the brackets that hold the panels to the rails are now in place. Since the PG&E meter isn't mounted on the house itself, they also had to dig a trench. Tomorrow a county planning dept. inspector will come by to make sure everything is to code.

I also got an email from PG&E today, informing me that they know I have solar being installed and will schedule an appointment to do their own verification and turn the system on, once the hardware is in place.

One subtlety, since I also want to connect a generator for when we get power cuts (I'm on top of the Santa Cruz mountains) we had to decide what order to wire everything together. The sequence is

PG&E service meter - Solar Power system - Generator - House breaker panel

The generator is only wired into a subset of the house circuits, so it is looped into the house breaker panel. When installed, it will have a sensor that can tell whether there is any incoming power from PG&E, and if not, it fires up after 20 seconds or so.

The solar power system detects the PG&E power, synchronizes to the 60Hz phase and adds its own power by providing a few volts more than PG&E, to get the power to flow into the system. If PG&E goes away, the solar system also shuts down, then the generator detects no power, isolates the downstream components and takes over powering the house.

At one point I looked at having batteries rather than a generator, but it is a lot less efficient, they don't last very long and they are far more expensive. A 6KW battery system with inverter was around $10K, while I can get a 8KW propane generator for $2K, and I'm thinking of putting in a 14KW Generac 5503 that is currently available from Amazon for $3.3K delivered, since that can supply a 40A 220V circuit for the heat pump. I'm likely to need it for up to a week each year, and that will be the only thing that uses propane at that point.