The UK National Grid Black-Start Survival Guide: Sizing LiFePO4 & Solar for British Winters

# OFF-GRID ACADEMY FIELD MANUAL 03 ## The UK National Grid Black-Start Survival Guide: Sizing LiFePO4 & Solar for British Winters ### 1. The British Winter Solar Reality Many preppers buy a 100W solar panel assuming it yields `100W × 12 hours = 1,200Wh/day`. In reality, the UK sits between **50°N and 59°N latitude**. In December and January, overcast skies reduce average irradiance to **0.5 to 0.8 Peak Sun Hours (PSH)** per day. A 400W folding ETFE array in winter yields roughly **200Wh to 450Wh/day**—meaning battery capacity and ruthless load discipline are paramount. ### 2. Critical Load Audit (Typical UK Household / SME Office) | Appliance | Power Draw (W) | Duty Cycle (Hrs/Day) | Daily Energy (Wh/Day) | | :--- | :--- | :--- | :--- | | **Gas Combi Boiler (Pump + PCB + Fan)** | 95 W | 6 hrs (intermittent) | **570 Wh** | | **A++ Chest Freezer (Insulated)** | 45 W (avg when running) | 8 hrs compressor run | **360 Wh** | | **868MHz LoRa Base + VHF Charger** | 8 W | 24 hrs | **192 Wh** | | **Citadel N100 / Pi 5 Offline Server** | 10 W | 12 hrs | **120 Wh** | | **LED Task Lighting (12V DC)** | 12 W | 6 hrs | **72 Wh** | | **TOTAL CRITICAL LOAD** | — | — | **1,314 Wh / Day** | ### 3. Battery & PV Sizing Formula To survive **3 full days (72 hours)** with zero solar input allowing for 85% inverter efficiency and 80% usable LiFePO4 capacity: ``` Required Battery Capacity = (1,314 Wh × 3 days) / (0.85 × 0.80) = 5,797 Wh (~5.8 kWh) ``` *Starter Tier:* A **2,048Wh LiFePO4 Power Station** (`EOD-PWR-009`) coupled with a **400W ETFE Solar Array** (`EOD-PWR-010`) sustains this critical load for **48–60 hours** immediately, or **7+ days** if you cycle the freezer for 4 hours/day and run the boiler only morning and evening. ### 4. Powering Your Gas Boiler Safely in a Blackout 80% of UK homes have mains gas heating that dies in a power cut solely because the **230V electronic PCB and circulation pump** lose power (even when National Gas pipeline pressure remains positive for days). - Have a qualified electrician replace the hardwired 3A fused connection unit (FCU) next to your boiler with an **unswitched BS 1363 13A socket + 3A fused plug**. - Note: Some modern flame-rectification boilers require a **Neutral-Earth bond plug** when run from a floating-neutral portable inverter so the ionization probe detects the flame.