How to Size a Solar Power System for Your Bug-Out Location
Get the math right once and your off-grid location runs on free sunlight indefinitely.
The single biggest mistake in off-grid solar is guessing at system size. Under-build and your batteries die every cloudy day. Over-build and you spend $5,000 more than necessary. The right system is sized to your actual load — what you need to power, how long per day, and how many days of battery backup you need without sun. This guide walks through the complete sizing process step by step, with specific product recommendations at each tier.
Step 1 — Calculate Your Daily Power Consumption
List every electrical device you plan to run at your bug-out location, its wattage, and how many hours per day you’ll use it. Multiply watts × hours = watt-hours (Wh) per day for each device. Add them all up for your daily total.
| Device | Watts | Hours/Day | Wh/Day |
|---|---|---|---|
| LED lighting (4 bulbs) | 40W | 5 hrs | 200 Wh |
| 12V compressor fridge | 50W avg | 24 hrs | 1,200 Wh |
| Phone/tablet charging | 30W | 2 hrs | 60 Wh |
| GMRS/Ham radio (receive) | 5W | 8 hrs | 40 Wh |
| GMRS/Ham radio (transmit) | 50W | 0.5 hrs | 25 Wh |
| Laptop | 65W | 3 hrs | 195 Wh |
| Water pump (12V) | 60W | 1 hr | 60 Wh |
| Daily Total | 1,780 Wh/day |
This example loads to 1,780 Wh/day — a realistic bug-out cabin setup for 2–4 people. Your number may be higher or lower depending on your appliances. Round up by 25% for inefficiency losses: 1,780 × 1.25 = 2,225 Wh/day target.
Step 2 — Size Your Solar Panels
Solar panels are rated in watts at peak output (direct sunlight, optimal angle). In practice, a panel produces its rated output for approximately 4–6 “peak sun hours” per day depending on your location and season. To size panels: Daily Wh ÷ Peak Sun Hours = Watts of Panel Needed
For our 2,225 Wh/day target: 2,225 ÷ 4.5 peak sun hours = 494 watts of panel. Round up to 500W–600W for a safety margin.
Renogy 100W Monocrystalline Panels — Build a 600W Array
21.3% Efficiency5-Year Material Warranty25-Year Power WarrantyWeatherproofThe Renogy 100W monocrystalline panel is the industry standard for off-grid solar builds. Six of these panels wired in series-parallel gives you a 600W array — enough to cover our example load with room for cloudy-day buffer. Renogy 100W panels on Amazon →
Shop Renogy Solar Panels on Amazon →Jackery SolarSaga 200W — Portable Panels for Vehicle/Cabin
Foldable Design200W Single PanelIntegrated KickstandNo Mounting RequiredFor a portable bug-out location that isn’t a permanent cabin, the Jackery SolarSaga 200W foldable panel deploys in seconds with no mounting hardware. Three panels wired to a compatible charge controller gives you 600W of portable generation that packs into a vehicle or trailer. The integrated kickstand adjusts angle toward the sun throughout the day.
Shop Jackery SolarSaga on Amazon →Step 3 — Size Your Battery Bank
Your battery bank needs to store enough energy to run your loads through nights and cloudy days. A standard design provides 2–3 days of autonomy without solar. For 2,225 Wh/day × 3 days = 6,675 Wh of storage needed.
LiFePO4 batteries can be discharged to 80–90% of capacity without damage. Lead-acid should only be discharged to 50%. Recommendation: LiFePO4 for all new off-grid builds.
6,675 Wh ÷ 12V ÷ 0.85 usable = 655 Ah of 12V LiFePO4 battery. Use two 200Ah batteries in parallel (400Ah, covers approximately 2 days) as a starter bank and expand as budget allows.
Battle Born 100Ah LiFePO4 Battery — The Gold Standard
3,000–5,000 Cycle LifeBuilt-In BMS10-Year WarrantyFully Parallel-ableBattle Born batteries are the most trusted LiFePO4 brand in the off-grid and overlanding community. Built-in battery management system (BMS) protects against overcharge, overdischarge, and temperature extremes. At 3,000–5,000 cycles to 80% capacity, a Battle Born battery lasts 8–14 years of daily use — longer than any lead-acid alternative. Battle Born 100Ah LiFePO4 on Amazon → — buy in matched pairs or quads for your target bank size.
Shop Battle Born Batteries on Amazon →Budget Option: Ampere Time 200Ah LiFePO4
200Ah Per UnitBuilt-In BMS2,000+ CyclesHalf the Cost of Battle BornThe Ampere Time 200Ah LiFePO4 battery delivers solid performance at roughly half the cost of Battle Born. Two units in parallel gives you 400Ah — enough for 2+ days of autonomy in our example system. Good choice if you’re building a starter bank with plans to upgrade later.
Shop Ampere Time on Amazon →Step 4 — Charge Controller and Inverter
Renogy Rover 60A MPPT Charge Controller
MPPT TechnologyUp to 800W InputLiFePO4 CompatibleLCD DisplayThe charge controller sits between your panels and batteries, managing charging voltage and current. An MPPT (Maximum Power Point Tracking) controller captures 20–30% more power than a PWM controller — especially valuable in partial shade or low-light conditions. The Renogy Rover 60A MPPT handles up to 800W of panel input, has a LiFePO4 charging mode, and includes a Bluetooth monitoring module for real-time status from your phone.
Shop Renogy Rover on Amazon →Giandel 3000W Pure Sine Wave Inverter
Pure Sine Wave3000W Continuous6000W SurgeAC + USB OutletsAn inverter converts your 12V battery power to 120V AC for running appliances. Always use a pure sine wave inverter — modified sine wave inverters damage sensitive electronics and run motors inefficiently. The Giandel 3000W pure sine inverter handles continuous loads up to 3,000W with 6,000W surge capacity for motor starts. Includes multiple AC outlets and USB ports for direct device charging.
Shop Giandel Inverter on Amazon →Complete System Summary by Budget
| Budget Tier | Panels | Battery | Inverter | Est. Cost |
|---|---|---|---|---|
| Starter (1–2 people) | 200W Renogy kit | 100Ah LiFePO4 | 1000W inverter | $600–900 |
| Mid-Range (2–4 people) | 400W Renogy | 200Ah LiFePO4 | 2000W inverter | $1,500–2,200 |
| Full Off-Grid (4–6 people) | 600W Renogy | 400Ah Battle Born | 3000W inverter | $3,500–5,500 |
⚠ BUY YOUR CHARGE CONTROLLER LAST: Size your charge controller to your final panel array, not your initial build. Most off-grid builders expand their panel array within the first year as they understand their actual usage. Buy a controller with 20–30% headroom above your current panel array so it doesn’t become the bottleneck when you expand.
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