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Off-grid solar

Off-Grid Solar System Cost Calculator

Cost calculator for off-grid solar + battery systems sized by daily kWh load. From weekend cabin to full-electric homestead, plus grid-tied with whole-home backup.

Quick answer: weekend cabin $10,000–$23,000. Full-time cabin $23,000–$51,000. Modest homestead $40,000–$82,000. Full-electric homestead $66,000–$148,000. The 25D credit expired Dec 31 2025.

Off-grid solar PV array and battery bank at a rural property

Optional — auto-sets state

Installed cost · Full-time cabin (small home) · Montana

$35,200

range $23,000 – $51,200

PV array

4 kW

$11,000

Battery

20 kWh

$15,000

Inverter + install

$9,200

Off-grid economics: off-grid is expensive — grid power averages 16¢/kWh; off-grid power often costs 50-80¢/kWh over 20 years once you include battery replacement. The rationale is location (no grid), independence (preppers/homesteaders), or resilience (grid-tied with full-backup). The federal 25D credit covered off-grid solar through 2025-12-31 (now expired); state programs vary.
Cost simulatorMonte Carlo simulationSee the full range of likely installed costs — with the odds
Optimistic—10% chance under
Most likely—the single most-likely cost
Safer budget—90% chance under

Run a Monte Carlo of 10,000 possible outcomes to see the full distribution and the single most-likely installed cost.

Press Run simulation to roll 10,000 scenarios and watch the odds take shape.

  • PossibleBattery bank wiring or enclosure upgrade+$800–$3,500
  • PossibleGround-mount foundation or extra racking+$1,000–$4,000
  • PossibleBackup generator / auto-start integration+$1,500–$6,000

Surprise odds are approximate planning estimates, not measured rates; cost ranges are sourced where shown. How this works.

Each cost line is drawn from a triangular distribution and correlated by a shared market factor (~0.5); the most-likely value and range emerge from the simulation, not the band. A planning simulation, not a quote.

New to off-grid solar?

Off-grid systems differ from grid-tied solar in three ways: bigger battery (you can’t export to the grid), beefier inverter (must run all loads simultaneously without grid support), and backup heat source (you can’t run a heat pump at design temperature on solar alone in winter). Most off-grid setups include a small wood stove or propane heat for the coldest weeks of the year.

Read the full guide

Frequently asked questions

How much does an off-grid solar system cost?

Weekend cabin basic (5 kWh/day): $10,000–$23,000. Full-time cabin (15 kWh/day): $23,000–$51,000. Modest homestead (25 kWh/day, gas heat): $40,000–$82,000. Full-electric homestead (40 kWh/day): $66,000–$148,000. Grid-tied with whole-home backup: $48,000–$107,000.

How big a battery do I need?

Industry standard: 2 days of average daily use. So a 15 kWh/day household needs ~30 kWh of usable battery storage (typically 40-60 kWh nominal). Lithium-iron-phosphate (LFP) chemistry — Tesla Powerwall, Enphase IQ Battery, Sol-Ark — is the modern standard for off-grid; replaces lead-acid which needed 4-5× nominal capacity.

Is the 25D credit available for off-grid solar in 2026?

No. The 30% Residential Clean Energy Credit (25D) for solar + battery expired Dec 31 2025 (OBBBA). 2026+ off-grid installs no longer have the federal subsidy. State programs vary — Vermont, Maine, and New York still offer modest credits.

Off-grid vs grid-tied with backup — which makes sense?

Off-grid only makes sense if you literally cannot connect to the grid (location), the grid extension cost exceeds the off-grid system cost, or you have a strong philosophical preference. For 99% of homeowners, grid-tied solar + battery with off-grid capability (Sol-Ark, Outback Skybox) is the better engineering — you get backup during outages but use the grid as a free, infinite battery the rest of the time.

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