Establish your site parameters. Structure type, climate zone, and scenario type
determine the scale requirements for everything downstream.
Used to calculate optimal solar tilt angle for your location. US zip codes only.
Module 1 of 7
MODULE 02
Critical Load Assessment
Inventory every electrical load in your plan. Assign each to a tier:
Tier 1 (life-safety — never shed),
Tier 2 (comfort / operational), or
Tier 3 (convenience — first to cut when supply is limited).
Don't forget standby / always-on loads. Security cameras (10W × 24 hrs = 240 Wh/day each), NVR/DVR systems, alarm panels, ham radio on receive, network switches, and medical devices that run continuously are easy to miss but matter significantly in a tight system. Enter their running wattage with 24 hrs/day.
Click any row to edit
Description
Category
Watts
Hrs / Day
Wh / Day
Tier
Action
No loads added yet. Click ADD LOAD or QUICK ADD PRESETS to begin.
Tier 1 · Critical
0 Wh
0 kWh/day
Tier 2 · Operational
0 Wh
0 kWh/day
Tier 3 · Convenience
0 Wh
0 kWh/day
Total Daily Load
0 Wh
0 kWh/day
MODULE 03
Generation Sources
Document all power generation assets. The planner calculates total available
daily generation and compares it against your Module 02 loads.
⚙ GENERATORS
No generators added. Click + ADD GENERATOR.
☀ SOLAR ARRAY
Used for NEC 690.8 CC sizing: Isc × parallel strings × 1.25. Always on the panel spec sheet.
Used to calculate string Voc for controller sizing. If unsure, enter 1.
★ For preparedness: use your worst-month value (typically December/January), not the annual average. Summer peak hours can be 30–50% higher than winter. Sizing to annual average produces a system that fails exactly when you need it most. Search "PVWatts [your city]" for monthly data.
Accounts for inverter losses (~5%), wire/cable losses (~2%), temperature derating (~4%), dust/soiling (~2%), and BMS/balance-of-system losses (~1%). 0.77 is conservative. A well-designed system may reach 0.85–0.90. Note: panel output also drops ~0.4% per °C above 25°C — in hot climates (AZ, TX) this adds an additional 10–20% real-world loss on top of this factor.
📐 PANEL MOUNTING
Optimal fixed tilt ≈ your latitude. Enter your zip code in Module 01 for a site-specific recommendation. Year-round: use latitude. Winter-favored: add 10–15°. Summer-favored: subtract 10–15°.
Estimated Daily Solar Output
— Wh/day
⚡ ALTERNATIVE SOURCES
Most reliable source available — runs 24/7. A small stream with 50W continuous output produces 1,200 Wh/day. Consult Scott Hunt / Practical Preppers for site-specific hydro assessment.
⚡ GENERATION CAPACITY SUMMARY
Generator Daily Output0 Wh/day
Solar Daily Output0 Wh/day
Wind / Hydro / Alternator0 Wh/day
Total Generation0 Wh/day
Total Load Required0 Wh/day
Surplus / Deficit—
Recommended MPPT Controller Size— (enter solar array above)
Max Array Voltage Check (Voc)— (enter panel Voc in solar section)
⚠ Generator output is calculated at rated running watts × planned hours/day. Actual fuel consumption at partial load will be lower — your fuel calculations are conservative, which is the correct approach for preparedness planning.
MODULE 04
Battery Storage
Size your battery bank for the autonomy you need. Calculations are based on
your Tier 1 critical loads and your desired days of autonomy without running
generation equipment.
Leave blank if planning only. Enter your actual installed capacity to compare against requirements.
Bank Status vs. Requirement
— enter data above
LFP (lithium iron phosphate) is the current industry standard — 80% DoD, 3,000–6,000 cycle life, zero maintenance. FLA/AGM are legacy choices requiring watering, equalization charging, and ventilation.
48V is the standard for home-scale systems. Lower current at higher voltage means smaller wire gauge, less heat loss, and better inverter efficiency. 12V/24V only appropriate for small cabin or RV applications under ~2 kWh.
3 Days
Used to calculate battery count. Default: 100 Ah.
Sol-Ark / server-rack LFP systems typically use 48V modules. Wiring config and battery count depend on this.
Must exceed peak surge of highest-draw load. Standard motors/pumps: 3–5×. Deep well submersible pumps: 5–7× running watts at startup. Name loads with "deep well" or "submersible" to get the correct 6× estimate.
MPPT is strongly recommended — up to 30% more harvest than PWM, especially in partial cloud conditions.
Common limits: Sol-Ark 6K/8K/12K = 150V · Sol-Ark 15K = 200V · Victron MultiPlus-II = 200V · Outback Radian = 150V · Standalone MPPT (Victron SmartSolar 150/100) = 150V. String Voc must stay below this at coldest expected temperature.
Cold significantly reduces usable battery capacity. LFP retains ~90% at 0°C but drops to ~65% at -20°C. FLA/AGM degrade faster: ~80% at 0°C, ~40% at -20°C.
Plan fuel reserves for each generator. The planner calculates days of runtime
from current and planned stock, flags safety limits, and targets your
preparedness duration.
No generators configured. Return to Module 03 to add generators before
completing fuel planning.
🔥 PROPANE / ALTERNATE FUEL
Enter in pounds, not gallons. Common tanks: 20-lb BBQ = 20 lbs · 100-lb cylinder = 100 lbs · 500-gal tank ≈ 1,860 lbs · 1,000-gal tank ≈ 3,720 lbs. Convert: gallons × 4.24 = lbs.
Propane tanks are filled to ~80% capacity. A 500-gal tank holds ~400 usable gallons ≈ 1,490 lbs. Enter usable capacity.
Storage Safety: OSHA max 25 gallons gasoline inside a structure.
Use approved safety containers. Add stabilizer (PRI-G or STA-BIL) within 72 hrs
of purchase. Rotate quarterly. Diesel can gel in cold — store in insulated or
heated space below 32 °F.
MODULE 06
Backup Tier Plan
Using your tier assignments from Module 02, define the conditions under which
you step down power levels. This becomes the operational load-shedding SOP in
your final plan document.
📋 TRIGGER CONDITIONS
SoC thresholds by chemistry: LFP — step down at 70% SoC, critical at 50% SoC (BMS hard cutoff typically at 20% — never plan to reach it). FLA/AGM — step down at 75% SoC, critical at 60% SoC (sulfation risk below 50%). If your system lacks a SoC display, use voltage: 48V LFP system → 51.2V = ~70% · 50.4V = ~50%. Check your inverter display.
MODULE 07
Gap Analysis
Side-by-side comparison of what your system needs vs. what you have.
Critical gaps are flagged and prioritized. Generate your plan when ready —
the output includes a complete printable power systems document.
All modules reviewed. Ready to generate your power plan.
Click any preset to auto-fill the form. Confirm hours and tier before saving.
Category determines startup surge estimate: Water 3× · HVAC 2.5× · Tools 2× · Refrigeration 1.5× · Cooking 1.2× · Medical/Comms/Security/Lighting/Other 1.0× (electronic/resistive loads). Deep well pumps ("submersible") use 6×.
For refrigerators/freezers: use average daily draw, not compressor peak. Compressor duty-cycle is typically 25–40%. A 150W compressor cycling 33% of the time = 50W avg. Enter 50W × 24 hrs, or use the preset "avg" values.
Daily Consumption— Wh/day
Add Generator
Enter the spec-sheet value at rated load. At 50% load, actual runtime is typically 30–50% longer. This tool uses your entry to calculate fuel consumption rate — conservative by design.