Easy, self-install solar for your condo rooftop, balcony or back yard

Create power from the sun for backup, savings, or energy independence.

1.2kW solar panels removably placed on the apartment's roof & "sunbox" downstairs: 3kW controller/inverter/UPS & 2.5kWh battery powering the apartment

How it works

  • Backup for power outages. It's like a UPS (uninterruptable power supply) that primarily charges from sunshine. We don't even notice power outages or public safety shut-offs anymore (same would go snowstorm outages or hurricane outages elsewhere).
  • Saves you money the rest of the year until the sun is down & battery is empty, then falls back to the grid. It generally pays for itself in 4 years with those savings.

Benefits

  • Built To Go - take it with you if you move. Throw it in the back of a truck. Nothing is permanently attached or wired in. The Sunpower T5s are built to withstand up to 120 mph winds while lying on the roof.
  • Landlord-friendly - Non destructively place panels on your roof without making holes. I did ask my landlord for permission as a common courtesy.
  • Plug-in Hybrid - In normal operation the system runs off solar & battery, but can seamlessly flip to utility pass-through mode if both other sources are exhausted. Like a plug-in hybrid car can avoid range anxiety with a backup gas engine for long trips, the system removes the worry of running out of power if you go over your self-generation that day.
  • Utility-friendly - This system is off-grid as far as the utility is concerned. It never feeds back into the grid, only ever drawing if necessary.

Tracking

You can track the usage and inputs with an app - I got a (bad and expensive) tracker dongle but I'd strongly recommend Solar Assistant

Stored sunlight runs the place

Stored sunlight runs my kitchen, dining & living room - fridge, induction stove (Ikea, placed on gas stove), kettle, entertainment system, and everything else. It could also run microwaves and space heaters. It doesn't run my lights - it's a PITA to get an alternate power system to everywhere I want lights. But LEDs nowadays are in the 2-5 watt range, so consumption of those is minimal. The system powers all of my high-power devices above, which makes a way bigger dent with fewer cables.

The Secret Sauce

The secret sauce is that the sunbox is usually off-grid and never pushes power back into the grid. The only reason it's connected to the wall at all is that if it runs out of power it can pull energy from the wall. The sunbox (and its satellite on the roof - the solar panels) are acting as a "solar buffer" between your devices and the wall. It's not wired into the meter, doesn't require a permit, etc.


Wall plug for pass-through UPS mode & cables through window-gap to solar panels

The Downside

The potential downside is that you need to run your own "alternate electricity system" through the house (ie. long white extension cables) to each room, as you're side-stepping the house's built-in wiring in the walls and using your own that you can redirect to the sunbox.


Main 2,500W power distribution strip. Relatively neat wiring from the box to the fridge, induction cooktop and on to the living room.

Components & Cost - $1,124 total

$200 for 1.2kW solar (used) - 4 x 320W Sunpower T5s @ $50 - though if there's no used panels near you then new ones 4 x 455W = $746 is great too

$494 for 3kW inverter/controller/UPS all-in-one - 3kW pure sine wave inverter, 4kW MPPT solar charge controller, UPS function - falls back to grid when battery empty

$418 for 2.5kWh LiFePo4 battery

Cables / Tender:

  • https://amzn.to/43NkcuJ - $14.79
  • https://amzn.to/4cwxY8Y - $30.42
  • https://amzn.to/4cuS3fx - $13.00
  • https://amzn.to/43u3ikz x2 - $17.00
  • https://amzn.to/43u3r7B - $12.99
  • https://amzn.to/43y5Qhx - $8.89
  • Total: $114.09

=> $1,124 total

Remote tracking (optional):

  • https://amzn.to/3Vs3COI - $7.99
  • https://amzn.to/3TPaXGI - $23.92
  • https://amzn.to/4a6UMdI - $6.99
  • https://solar-assistant.io - $55.83
  • Total (additional): $94.73

How to guide

Coming soon

Financial Payback & Embodied Energy

Financial payback period for 3000W
System cost : $1,124 on Amazon in 2024
Yearly energy creation: 365d * 4.26hsun/d * 1.280kW = 2,000kWh/y (but more like 1,000kWh/year after losses)
Yearly value creation: 1,000kWh/y * $0.55/kWh in SF = $550/y energy created
100W system payback period: $1,124 / $550 = 2 years until payback

How green is it:

Production footprint PV (source): 2,900kWhee/kW * 1.28kW = 3,712kWh embodied energy

Production footprint LiFePo4 battery (source): 106kWhee/kWh * 2.4kWh = 254kWh embodied energy

Annual energy production system: 1100kWh/y Payback period: 3966kWh / 1100kWh/y = 3.5 year footprint payback

FAQ

What’s the catch? Seems to good to be true? Well, this thing sits between your devices and the wall. So you need to neatly run extension cables from every room in the house to the “sun box”, and then run one cable from the box to the panels, and another to the wall (optional, just so it can fall back to pulling power from the wall). Photos of this are coming soon.

Will it ever push power back into the wall? Nope! It’ll only ever draw from the wall in the event that both the sun is down and the battery is dead (so your fridge won’t go off overnight for example).

Is this legal? Yes, see above. No difference to plugging your fridge into your wall, as far as the utility is concerned.

Want some help?

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