Two Waters · Jay Birkett

A solar-powered house I wired myself.

2.32 kW of panels, a hand-built 8 kWh battery, and Home Assistant running 91 automations. I designed it, installed it, and it powers the house every day. The numbers on this page are live.

String A · 4 × 350 WString B · 2 × 460 WVICTRON MPPT ×2100 / 508 kWhLiFePO4Hand-built · 8S · JK BMSDC → AC4 kW inverter · HouseDC → AC3.5 kW · Office + ShedGridOctopus Agile40 A chargerTightWatt-controlled

The whole system at a glance — solar into a hand-built 8 kWh battery, then out to the house, office and shed; grid-charged only on the cheapest Octopus Agile slots by TightWatt.

Live system · from Home Assistant
System online
10.33 kWh
Generated today
93 %
Battery state of charge
2.32 kW
Array capacity
−£1.98
Grid cost today
Solar generation Battery SoC sample data
The system

How it fits together

Everything above is real kit that's installed and running. The diagram mirrors the actual wiring, and the readings come straight out of Home Assistant.

Solar to battery

Two Victron BlueSolar MPPT 100/50 controllers run the two panel strings. They charge a battery I built myself — 8 kWh of 8S LiFePO4 prismatic cells with a JK active-balancing BMS — which feeds two inverters: 4 kW for the house and 3.5 kW for the office and shed.

Buying power at the right time

When the battery needs a top-up, my TightWatt automation switches a 40 A mains charger on only during the cheapest half-hours on Octopus Agile — and holds out for negative prices when it can.

Build

It grew in two stages

Roof array photo — pending
Stage 1 — the original four-panel roof string (4 × 350 W).
Roof array photo — pending
Stage 2 — extended to six panels with a 2 × 460 W second string.
A real day

What it actually did

10.33 kWh
Generated (10 July 2026)
93%
Battery by evening
17 h+
Runtime at load
£1.98
Daily grid cost
Projects

Four things I've built and run

Each one is written up properly: how it works, the decisions behind it, and the numbers to back it up.

Questions

The stuff people ask

Did you really build all this yourself?

Yes. I designed the solar and battery setup, mounted and wired it, assembled the LiFePO4 pack from bare cells, and wrote the Home Assistant automations. The write-ups walk through the decisions and trade-offs along the way.

Is the data on this page live?

The panel near the top reads from Home Assistant. When it can reach my system it shows the current state of charge, today's generation and grid cost; otherwise it falls back to a representative day and tells you it's doing so.

Can I use TightWatt on my own battery?

Yes — it's a Home Assistant blueprint, free to import from GitHub. You point it at your battery, charger and Octopus Agile rates, set a target, and it does the rest. The TightWatt page has the full install guide.

What do you do for a living?

I'm an IT professional in the Microsoft 365 and Intune world, with MSP client work alongside it. The Certifications page lists the credentials; the projects here are what I build in my own time.

Want to talk shop?

Whether it's the solar build, the automations, or work — email is the best way to reach me.

Email me