Solar in California (ca 2024)

Here are some long-running notes on our solar system.

2024: Design

I recently spec’ed out a solar system. It’s not installed yet, but the contract is signed.

Our situation is:

I spent a lot of time thinking about the design, and the key principles were:

In California in 2024, you need a battery today since you’ll be on NEM 3.0, and it doesn’t pencil out without a battery. On the other hand, batteries will easily dominate the cost of a new installation. On the third hand, the energy storage landscape is changing extremely rapidly.

So I opted for “just enough” battery today and the end result is:

The Franklin system is price competitive with the Tesla PW3, but the key feature to me was the optional native support to connect a generator. Bonus of not not giving money to Elon.

The SS2-50 is IMO the best way to preserve optionality. Since it’s a standard, you can do things like hook up a “battery generator” to it, or even a car, if your vehicle supports it. You could use your external power source as a true emergency backup, or just as a way to add more storage to your system without having to get an electrician to do any expensive rewiring of stuff.

The SPAN is important for my home, since we are stuck with 125A service, and having software configurable load-shedding seems useful to keep overall load within limits. Better yet, it also integrates with the Franklin ecosystem and the SPAN Drive, so that you can do things like, “only charge the EV after I’m done charging the home battery”. The Drive doesn’t support V2H but that’s why the generator inlet is so key. We’re partially insulated from the standards evolving.

Last is the Backup by Biolite. Although this device isn’t shipping yet, I’m a backer on Kickstarter. I opted for the 3 kWh version to power my fridge. It’s cheaper $ / kWh vs the FranklinWH and allows me to underspec the house battery by 3 kWh. Also, it embodies the idea of horizontal scaling rather than vertical scaling.

This is all stuff that is under contract.

But also, there are two other appliances I’m strongly considering for the future.

They both implement the horizontal scaling idea, by bringing their own energy storage, and again, allow me to continue growing the overall storage capacity without too much additional, expensive, electrician work.

I hope to have real world usage data in a few months and will update here

2025: Installation

The install took about 2 weeks, mostly because the final design required about a 20 foot hand-dug trench from the house to the carport. Other than that, it was pretty standard.

From left to right, that is:

Local code required that there could be nothing flammable (ie, wood) over the battery. Since my house’s roof overhangs the perimeter of my house by about 5 feet all around, that meant I could not place the battery closer to my house unless I was willing to install a very expensive fire suppressant system. I was not willing to do this, so the next best place was by the carport.

This was the 20 foot hand-dug trench, plus building this mounting structure with a concrete base and enough space for 2 batteries. Although I only installed one.

2026: First Year Retrospective

This was the first year that we had solar!

I learned quite a lot. But first the stats.

Generated 8.8 MWh off a 7.4kW array.

Our actual usage was 6.4 MWh, which doesn’t align exactly with the numbers above, because our battery is not big enough to cover 100% of our needs 100% of the time, so we ended up importing from the grid during the winter months.

The app estimates we saved about $2200 in energy costs, which feels approximately correct. The payback period for this installation is unfortunately still extremly long, but hey, we avoided creating 3.4 tons of CO2. In California, that seems to be worth about $25 per ton at cap-and-trade auctions, so I’m going to claim an additional $85 of value.

So what did I learn in my first year of solar?

I was (predictably) obsessed with the stats generated by the system for the first 6 months, constantly checking in on the various apps to see what was going on. But after a while, I mostly stopped worrying about it.

I ran the battery down to 5% reserve for most of the year to maximize cost savings, but at times, when major storm warnings occurred, I bumped the reserve up to 70% to hedge against a grid outage. We got pretty lucky here, never actually losing grid power, but it was nice peace of mind.

Our usage is fairly consistent the entire year. We don’t have an A/C, and we have a gas furnace, whose electric blower consumes about 1 kW when running. Our system isn’t sized to cover the winter months – our 7.4 kW array isn’t big enough to fully charge our 13 kWh battery, and a 13 kWh battery wouldn’t cover our daily usage.

If we really wanted to be fully self-sufficient during the winter months, we’d need to double our storage capacity and probably triple our generation capacity, both of which would be extremely cost-prohibitive in 2025 prices. Plus, I’m still waiting for the EV industry to standardize their V2H implementations because it seems criminal to pay $20K for a 13 kWh battery when it’s possible to buy an F-150 Lightning with a 100+ kWh battery for $60K and you can haul mulch with it.

I have not used the generator input at all, although I guess I’m glad to have it.

The Biolite Backup hasn’t shipped because of normal Kickstarter engineering growing pains, but also because of the tariffs. Fuck Donald Trump.

We haven’t done any remodels so battery-powered induction cooktops are still a pipe dream.

Cars. Ugh.

In 2025, we drove:

These numbers reveal how utterly wasteful driving is. My car commute is ~20 miles round trip, which requires 5.1 kWh of electricity, while the entire house consumes between 10 – 15 kWh per day.

It’s depressing to see how energy intensive it is to move that much mass around. Anyway…

Figuring out where this electricity came from is a bit of an exercise, since I charge at home and at work. When charging at home, my SPAN smart panel is typically set up so that it will only charge the car after the house battery is full, and I typically do not pull from the grid.

This strategy works most of the year, but in the winter time, there are stretches where I do need to import from the grid specifically to charge the car, so I reconfigure SPAN to pull from the grid.

The net is that almost all of my car charging actually comes from my own solar panels, thus making our Bolt extremely clean to operate.

Anyway…