The four off-grid scenarios
| Scenario | Typical sizing | Key design considerations |
|---|---|---|
| Seasonal cabin / cottage | 2–6 kW solar, 10–25 kWh battery, small generator | Used weekends + summer weeks. Off-season demand is minimal. Often gets by without a generator if usage is light. |
| Year-round off-grid home | 8–15 kW solar, 30–60 kWh battery, generator | Full residential loads (refrigerator, water pump, HVAC, lights, computers). Generator essential for winter low-sun periods. |
| Remote utility (well pump, gate, fence) | 0.5–3 kW solar, 5–15 kWh battery | Specific load (well pump, security gate, electric fence). Sizing matches the load duty cycle. Generator rarely needed. |
| Rural homestead with grid available but distant | 12–25 kW solar, 60–120 kWh battery, generator | Often choosing off-grid because utility extension cost is $50,000+. Sized like a small commercial system. |
How off-grid sizing actually works
The math is different from grid-tied. Three driving inputs:
- Daily load (kWh/day): What you actually use. Off-grid budgets are usually tighter than grid-tied because generation is fully on you.
- Days of autonomy: How many sunless days the battery must carry. 1 day for cabins with a generator backup, 2–3 days for year-round homes, 5+ days for sites without practical generator access.
- Worst-month sun-hours: Off-grid is sized to the worst month, not the average. In Minnesota that's December (~2.5 sun-hours/day). In Arizona it's still 4–5 hours but with snowstorm reductions.
Battery sizing formula:
Battery kWh = (Daily load × Days of autonomy) ÷ (Depth of Discharge × Round-trip efficiency)
For LFP chemistry (most modern off-grid batteries): DoD ~95%, round-trip ~92%. So if your daily load is 12 kWh and you want 2 days of autonomy: 12 × 2 / (0.95 × 0.92) = ~27 kWh of battery capacity.
PV sizing formula:
PV kW = Daily load ÷ (Worst-month sun-hours × System efficiency)
System efficiency in off-grid (after wiring, charge controller, battery round-trip, inverter) is typically 70–75%. So 12 kWh/day ÷ (2.5 hr/day × 0.72) = ~6.7 kW PV in a Minnesota December scenario.
Generator sizing:
A generator should be sized to (a) carry the home's largest single load comfortably, and (b) recharge the battery faster than you discharge it during a generator-running period. Most off-grid year-round homes use 6–14 kW LP/propane generators (Generac, Kohler, Cummins). The generator runs only when the battery falls below a configured threshold, usually managed by the hybrid inverter.
Equipment selection — what works off-grid in 2026
Inverter / charger (the heart of the system)
| Inverter | Off-grid suitability | Notes |
|---|---|---|
| Sol-Ark 12K / 15K / 30K-3P | Excellent | Designed for hybrid use including off-grid. Strong generator integration, MPPT solar input, robust user community. Default choice for serious year-round off-grid homes. See hybrid inverter guide. |
| EG4 18kPV / 12000XP | Excellent | Lower cost than Sol-Ark with similar capability. EG4's stack-mountable batteries pair cleanly. Best $/kW value at the high end of residential off-grid sizing. |
| Schneider Electric XW Pro | Excellent | Long-running off-grid favorite. Higher up-front cost but best-in-class generator integration and 24V/48V battery options for legacy systems. |
| Outback Radian / FXR | Good | Outback was the original off-grid inverter brand. Capable but increasingly displaced by Sol-Ark / EG4 / Schneider for new installs. |
| Victron MultiPlus / Quattro | Excellent (smaller scale) | European brand popular for cabins, RVs, marine, and small off-grid setups. Highly configurable; less common for full-home off-grid in the U.S. |
| Tesla Powerwall 3 | Limited | Designed primarily for grid-tied with backup. Off-grid mode exists but Tesla's ecosystem and cellular monitoring assume grid presence. Not the right pick for a real off-grid home. |
| Enphase IQ8 + IQ Battery | Limited | Same caveat — Enphase is grid-following microinverter architecture with battery added. Off-grid operation is supported via "Sunlight Backup" but limited to short-duration sunlight-driven loads. |
Battery chemistry
LFP (lithium iron phosphate) dominates off-grid in 2026. Reasons: temperature stability, long calendar life (15–20 years), deep cycling tolerance, low fire risk vs. NMC. Common picks:
- EG4-LL or EG4-LL-S server-rack batteries: 5–10 kWh per unit, stack to 60+ kWh for under $500/kWh installed. Most popular off-grid choice in 2026.
- Pytes V5 / V48 server-rack: similar form factor, slightly different BMS. Good with Sol-Ark and EG4.
- SOK 48V batteries: Premium LFP with long warranty.
- Discover AES Energy Storage: Higher-end commercial-grade, used on serious year-round off-grid homes.
- HomeGrid Stack'd: Modular 4.8 kWh modules, popular Sol-Ark companion.
What's fading: Lead-acid (AGM, gel, flooded) is increasingly relegated to legacy systems and small cabins. The cost-per-cycle math no longer favors lead-acid against LFP for new builds. NMC chemistry batteries (older Tesla Powerwall, some Generac) are mostly being replaced by LFP across the industry.
Solar modules (PV)
Off-grid module choice mirrors grid-tied: U.S.-assembled or allied-country modules with 25–30 year product warranties, bifacial gain in snowy climates, robust racking rated for the local snow and wind loads. See best solar panels.
Generator
For year-round off-grid, you almost certainly want a generator. Common picks:
- Generac Guardian 16-22 kW air-cooled LP/NG — most common residential off-grid generator. ~$5,000–$8,000 installed.
- Kohler 14-26 kW — equally popular with somewhat more rugged build for harsh-winter duty cycles.
- Cummins QuietConnect 10-22 kW — quieter operation, appreciated on lakefront cabins.
- Diesel generators — common in remote sites where propane delivery is impractical, or where the existing fuel infrastructure is diesel.
The generator should auto-start under inverter control when battery state-of-charge drops below a set point (typically 30–50%) and shut off when battery reaches the target charge. This pattern minimizes generator runtime — you don't run it for hours, you run it for an hour to bulk-charge the battery, then run on stored energy until the next bulk-charge cycle.
Off-grid vs. grid-tied with battery — key design differences
| Design factor | Off-grid | Grid-tied with battery |
|---|---|---|
| Sizing target | Worst-month sun | Annual average + utility offset |
| Battery capacity | Days of autonomy (can be 2–5+) | Hours of essential-load backup (8–24) |
| Backstop | Generator | Grid (and optionally generator) |
| Inverter type | Off-grid-capable hybrid (Sol-Ark, EG4, Schneider) | Hybrid or AC-coupled battery (Powerwall, Enphase) |
| Net metering | N/A | Often the primary economic driver |
| Federal §48E ITC eligibility | Yes for commercial/farm if FEOC-compliant | Yes for commercial/lease/PPA if FEOC-compliant |
| Code requirements | NEC 706 (battery) + 690 (PV); NEC 690.12 rapid shutdown applies if conductors enter occupied building | Same NEC + IEEE 1547 grid interconnection |
Cost ranges (2026 illustrative)
| System | Typical cost (installed) |
|---|---|
| Cabin: 3 kW PV + 14 kWh LFP + small inverter (no generator) | $15,000–$22,000 |
| Cabin: 6 kW PV + 20 kWh LFP + Sol-Ark 12K + 14 kW LP generator | $32,000–$45,000 |
| Year-round off-grid home: 12 kW PV + 45 kWh LFP + Sol-Ark 15K + 22 kW generator | $70,000–$95,000 |
| Larger off-grid homestead: 20 kW PV + 80 kWh LFP + dual inverters + diesel generator | $110,000–$160,000 |
| Remote well pump shelter: 1.5 kW PV + 8 kWh LFP + small inverter | $6,000–$12,000 |
Cost-saving tips that work off-grid:
- EG4 over Sol-Ark if your installer is comfortable with EG4. The price delta on a $70K system can be $5,000–$8,000 with no functional sacrifice for most use cases.
- Server-rack LFP batteries (EG4-LL, Pytes) over branded battery cabinets. Typical savings: $200–$300/kWh installed.
- Right-size the generator. A 14 kW LP generator is plenty for most year-round homes; bigger isn't better off-grid because the generator only runs to bulk-charge the battery.
- Plan for expansion. Pick an inverter and battery system that can scale (Sol-Ark, EG4, server-rack LFP) so you can add capacity later without replacing everything.
Off-grid code considerations
Off-grid systems still have to comply with electrical and building codes that apply to your jurisdiction:
- NEC Article 690 (Photovoltaic Systems): Module-level rapid shutdown applies if conductors enter an occupied building. A detached PV equipment shed can be exempt.
- NEC Article 706 (Energy Storage Systems): Listed equipment, working clearances, and disconnect requirements apply.
- NFPA 855: Battery placement and aggregate-capacity limits. Indoor residential limits typically ~20 kWh; larger banks need a detached structure or outdoor-rated cabinet.
- IEEE 1547 grid-interconnection rules: Don't apply to off-grid (no grid connection) but most modern hybrid inverters are listed UL 1741 SB anyway, which makes it easier to add grid-tied operation later if utility power becomes available.
See building & electrical codes for the complete framework.
Off-grid sizing pitfalls to watch in a bid
- Sizing to average sun, not worst-month sun. Off-grid systems must be sized to the worst month. A bid that uses annual-average sun-hours will under-deliver in winter.
- Skipping autonomy days. A "1-day autonomy" off-grid system fails on cloudy stretches. Year-round homes should target 2–3 days minimum.
- Underspec'd generator integration. If the inverter can't auto-start the generator, you're managing the system manually — not viable for unoccupied cabins.
- Tesla / Enphase pitched as off-grid. These are grid-tied-with-backup architectures, not off-grid-first. Steer toward Sol-Ark, EG4, or Schneider for real off-grid duty cycles.
- Lead-acid in a 2026 bid. If a bidder is still spec'ing flooded or AGM lead-acid for a new install, they're optimizing for up-front cost at the expense of cycle life and replacement schedule. LFP is the right answer for new off-grid builds.
- Missing winter design analysis. Snow loading, panel pitch, and snow-shedding behavior all matter more off-grid because you can't lean on the grid when production drops.
Got an off-grid bid? Make sure the math works.
Upload your off-grid solar proposal — the analyzer flags worst-month sizing gaps, undersized batteries, generator-integration issues, and equipment choices that don't match a real off-grid duty cycle.
Analyze My Bid →Frequently asked questions
Do off-grid systems qualify for the federal tax credit?
For homeowners on a residential cash purchase: no — the §25D residential credit expired Dec 31, 2025. For commercial, agricultural, and rental property off-grid systems: yes, the §48E commercial ITC applies (subject to FEOC compliance). See federal tax credit guide.
Can I go off-grid even if utility power is available?
Yes — some homeowners do for resilience or principle. The math rarely beats grid-tied with battery backup if you have grid available. Off-grid loses net metering and generally requires meaningfully larger battery and PV sizing.
How much does a generator add to an off-grid build?
$5,000–$10,000 for residential 14–22 kW LP/natural gas generators including auto-transfer integration. Diesel can run higher depending on tank requirements. Generator cost is small relative to the value of having a real backstop on a year-round off-grid home.
What about water heating and HVAC off-grid?
Most year-round off-grid homes use propane or wood for water heating and space heating because electric resistance heat would require massive PV/battery. Mini-split heat pumps work for milder climates and shoulder seasons. Cooktop is often LP. Keeping the major heat loads off the electrical system is part of the design discipline.
Will my homeowner's insurance cover off-grid?
Most insurers do, but call before signing. Some require permitting and inspection records. Some have specific policy language for solar-only homes. Document everything (permits, inspections, equipment listings) for the underwriter.
Can I expand later if the family grows?
Yes if you pick an expandable architecture: Sol-Ark or EG4 + server-rack LFP batteries scale by adding battery modules and possibly a second inverter. Cabin systems built around fixed inverter capacity are harder to expand.