Powering 7 Units from One Meter
Solar panels, batteries, smart panels, and the technology that makes one property feel like a mini power grid
The Power Problem
Our property has 7 units. Two in the existing duplex. Five new ADUs. All of them need electricity. But SDGE only allows one power connection per property (unless buildings are more than 150 feet apart -- ours aren't).
So how do you power 7 homes from one connection? The answer involves solar panels, batteries, smart panels, and a billing platform. Together, they turn the property into a mini power grid.
The Electrical Setup
The main electrical panel is 400 amps at 120/240 volts. Each unit gets its own 100-amp sub-panel. There are 8 meters total -- one for each of the 7 units plus one for shared house systems.
The electrical plans were done by Flores Engineering and approved by the city in January 2025.
Solar Panels
Every new roof gets solar panels. California requires it for new construction. But we're going beyond the minimum.
The key decision was whether to use individual inverters (one per unit) or a master system (one big system that feeds everyone). We chose the master system approach. It costs less up front and makes billing easier with the right tools.
Battery Storage
Each ADU gets a battery:
- Main house: Tesla Powerwall 3
- 5 ADUs: Enphase IQ Battery 5P (one per unit)
The batteries store extra solar power during the day. At night or during peak hours, the batteries power the units instead of buying expensive grid electricity. This is especially important under California's NEM 3.0 rules, which pay very little for solar power sent back to the grid.
The strategy: keep as much power on the property as possible. Don't sell it back to SDGE for pennies. Use it yourself or store it in batteries.
The Smart Panel
A company called Lumin makes smart electrical panels. These panels automatically send power where it's needed. If one unit is empty, the solar power that would have gone there gets sent to another unit instead.
This is what makes the property work like a mini power grid. The smart panel decides in real time: does this unit need power from solar, batteries, or the grid?
Billing Tenants for Solar
Here's the interesting part. I generate solar power on my roof. My tenants use it. But how do I bill them for it?
A company called Energy311 solves this. They make software that:
- Tracks how much power each unit uses
- Knows whether that power came from solar, batteries, or the grid
- Creates a bill for each tenant
- Charges market rates for the solar power (which is still cheaper than SDGE rates)
Setup costs $99 per meter. Monthly cost is about $5 per bill. The tenants save money compared to SDGE rates. I make money from the solar I generated. Everyone wins.
Energy311 Pricing
| Item | Cost |
|---|---|
| Setup per meter | $99 |
| Monthly per bill | ~$5 |
| Tenant savings vs SDGE | 10-30% |
The Big Picture
This setup does three things:
- Cuts utility costs for tenants (solar is cheaper than grid power)
- Creates income for me (I bill tenants for solar power I generate)
- Maximizes incentives (batteries and solar qualify for state rebates)
It also makes the property more valuable. A 7-unit building with solar, batteries, and a smart power system is worth more than one that just plugs into the grid.
The Lesson
The days of just connecting to the power company and forgetting about it are over. In California, energy is a profit center if you design for it. Solar, batteries, and smart billing can turn your utility bill from an expense into income. But you have to plan for it during design -- not after construction.