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Grid-Down Power: Sizing, Solar, Batteries, and Protection
Educational preparedness information. Mains-voltage wiring and generator transfer connections must be done by a qualified electrician — backfeeding a generator into house wiring can kill line workers.
Start with the math, not the gadget
Two numbers decide everything:
- Peak watts — the biggest simultaneous load you must run. A phone charger is 10-20 W, LED lights 5-10 W each, a laptop 30-65 W, a router + modem 10-25 W, a CPAP 30-60 W, a fridge 100-200 W running but 600-1200 W at compressor start, a freezer similar, an induction plate 1,000-1,800 W, an electric kettle 2,000+ W.
- Watt-hours per day — load watts × hours. A modern fridge uses roughly 1-1.5 kWh/day (it cycles); comms + lights + phones maybe 0.3-0.5 kWh/day; a laptop workstation 0.5 kWh/day.
Match gear to the numbers: a 200-300 Wh power bank covers phones, lights, and a router for a day; a ~1 kWh station adds laptop and CPAP for a couple of days; a ~2 kWh station (now available under 18 kg) keeps a fridge cycling for roughly a day per charge — which is why solar input matters more than raw capacity for outages beyond 48 hours.
Solar recharging
Panels are rated at ideal conditions; real-world planning: a 100 W portable panel yields roughly 300-500 Wh on a decent day (much less in Nordic winters — plan 5-10x more panel or alternative charging at high latitudes in December). Rules: point panels within ~30° of the sun and re-aim every couple of hours; even light shade on one corner can halve output; keep panels cool and clean. A 400 W panel array + 2 kWh station is a realistic "fridge + comms indefinitely" summer setup. For permanent installs, an MPPT charge controller, LiFePO4 battery bank, and proper fusing are the modern standard — LiFePO4 gives 3,000+ cycles vs ~500 for lead-acid and tolerates partial charging.
Generators
Fuel generators deliver high power but need fuel logistics: a typical 2 kW inverter generator burns roughly 0.5-1 L of petrol per hour depending on load. Petrol stores ~6-12 months (longer with stabilizer); diesel and propane store for years — propane-capable dual-fuel generators pair well with the same 9 kg cylinders as your stove. Run generators outdoors, 5+ m from windows, exhaust pointed away: carbon monoxide from generators kills people in every major blackout. Run the fridge and charge batteries in generator "shifts" of 1-2 hours a few times daily instead of running it continuously — this cuts fuel use by 70-80%.
Protecting electronics
- Surge protection: a whole-home surge protector at the panel plus point-of-use surge strips for sensitive gear covers most spikes. Surge strips wear out silently — replace after major surge events.
- UPS: for routers, NAS, and computers, a line-interactive UPS with automatic voltage regulation (AVR) rides through sags, spikes, and short outages and gives you minutes to shut down cleanly. Size it: UPS runtime claims assume full load; at 50 W of network gear, even a small unit runs 30-60 minutes.
- EMP/severe solar storm (worst-case layer): the cheap insurance discussed in the preparedness community is Faraday shielding for spare electronics — a fully enclosed metal container (galvanized bin, metal ammo can, or nested cardboard-lined foil wrapping) with no gaps, contents insulated from the metal. Store: spare radios, a basic phone, USB sticks with documents, charge controllers, LED lights, and cables. Whether or not one expects such an event, the cost is a bin and an afternoon.
The unplugged baseline
Electricity-free fallbacks so power becomes optional for survival: wool blankets and sleeping bags rated below your climate's worst temperatures, headlamps + lithium primary batteries (10-20 year shelf life; alkalines leak), candles and an oil lamp with stored fuel, a thermos (boil water twice a day, hot drinks all day), hand-crank radio, paper maps, printed contact lists and manuals, board games and books. The goal of a power plan is to shrink the list of things that truly need power to: refrigeration, communication, light, and medical devices.