- Off-grid solar sizing starts with your daily load in Wh - multiply by 1.25 for losses, then size panels and batteries
- In most of the continental US, 1 watt of solar panel produces 4-5Wh per day on average annually
- Battery storage should cover 2-3 days of your daily load to handle cloudy weather and seasonal variation
- LiFePO4 battery chemistry is the only practical choice for permanent off-grid installations - 10+ year lifespan
- A proper off-grid system requires a charge controller, inverter, and battery bank - not just panels and a power station
Size your off-grid solar system by calculating daily load in watt-hours, multiplying by 1.25 for losses, then dividing by your winter peak sun hours to get the minimum panel wattage. Battery storage should cover 2-3 days of load without sun. LiFePO4 is the only practical battery chemistry for permanent off-grid installations.
Off-Grid Solar vs. Portable Power Stations
Before getting into system design, it's worth being clear about what we mean by "off-grid solar." A portable power station with solar panels is a portable off-grid power source. A dedicated off-grid solar system is a permanent installation designed to be a property's primary power source.
The difference matters because they serve different purposes, have different components, and require different levels of installation expertise. This guide covers both, but is primarily focused on the more substantial setup: dedicated solar systems for cabins, homesteads, and properties without utility power.
If you're looking for a portable solution to keep essentials running during outages at a grid-connected home, our home backup guide is more appropriate. This guide is for people building a primary power system for a property without grid access, or planning for true energy independence.
The Four Components of Every Off-Grid Solar System
Regardless of scale, every off-grid solar system has the same four elements. Understanding each one is essential before looking at any product or kit.
1. Solar Panels
Panels capture sunlight and convert it to DC electricity. The key specifications are wattage (how much power they generate in full sun), efficiency (how much of available sunlight they convert), and temperature coefficient (how much performance drops in heat). For most residential off-grid applications, monocrystalline panels are the correct choice — higher efficiency in the same footprint, better low-light performance, and 25-year warranties from reputable manufacturers.
Panel sizing is based on your daily energy consumption divided by your location's peak sun hours. A property in Arizona gets 5.5–6.5 peak sun hours per day. A property in the Pacific Northwest might get 3.5–4.5 in summer and 1.5–2.5 in winter. These numbers dramatically affect how many panels you need.
2. Charge Controller
The charge controller sits between the panels and the battery bank, regulating the flow of energy to prevent overcharging. There are two types: PWM (pulse width modulation) and MPPT (maximum power point tracking). MPPT controllers are significantly more efficient — typically 20–30% better energy harvest — and are the right choice for any system over 200W. PWM is only appropriate for very small, budget-constrained systems.
Renogy is the dominant mid-market provider for MPPT charge controllers with a strong reputation for reliability at accessible price points.
3. Battery Bank
The battery bank stores energy generated during daylight for use at night or during cloudy periods. Battery selection is the most consequential decision in an off-grid system and the one where the most money is wasted on the wrong choice.
Two chemistries dominate the current market: lead-acid and lithium (LiFePO4). Lead-acid batteries are cheaper upfront but deliver only 50% of their rated capacity safely (deeper discharge damages them permanently), last 3–5 years, and require maintenance. LiFePO4 batteries cost 3–4 times as much initially but deliver 80–90% of rated capacity, last 10–15 years, and require no maintenance. Over a 10-year period, LiFePO4 is typically cheaper. We recommend LiFePO4 for all new installations.
4. Inverter
The inverter converts DC battery power to AC for standard household appliances. Key specifications are continuous output wattage, surge wattage (for motor startup), and inverter type (pure sine wave vs. modified sine wave). Pure sine wave is non-negotiable for any system that will power motors, electronics, or sensitive equipment.
For larger systems, a hybrid inverter that handles both solar charging and battery management is the most efficient architecture. These eliminate the need for a separate charge controller.
How to Size Your System
Proper system sizing follows a three-step process:
Step 1: Calculate daily energy consumption (Wh/day)
List every appliance, its wattage, and how many hours per day you use it. Multiply wattage by hours to get Wh, then sum all appliances. Add 25% for system inefficiencies. This is your daily energy target.
Step 2: Size your battery bank
Your battery bank should store enough energy for your daily consumption multiplied by the number of cloudy days you want to plan for (typically 2–3 days). Divide by 0.8 (for 80% depth of discharge on LiFePO4) to get the required rated capacity.
Step 3: Size your solar array
Divide your loss-adjusted daily energy target from Step 1 by your location's winter peak sun hours. The 25% loss allowance is already included, so don't add it twice. This gives you the minimum panel wattage needed to recharge your battery bank on an average winter day.
Size your system for winter sun hours, not annual average. A system sized for summer will leave you chronically undercharged from November through February. This is the single most common sizing mistake in DIY off-grid installations.
Complete System Packages by Scale
Lights, phone charging, small TV, and a 12V compressor refrigerator. Suitable for weekend use and short stays. Not designed for continuous habitation or high-draw appliances.
Full-size refrigerator, well pump (1/3 HP), lights, devices, TV, router, and occasional power tools. Designed for year-round habitation with conservative usage habits.
Whole-home coverage including well pump, refrigerator, freezer, washer/dryer, HVAC, and workshop loads. Requires professional electrical design and installation. Typically includes backup generator integration for extended cloudy periods.
All-in-One Solar Generator Kits vs. Component Systems
For small and medium systems, all-in-one solar generator kits — like EcoFlow's Delta Pro with solar panels, or Renogy's complete kit packages — offer a compelling alternative to building from individual components.
| Factor | All-in-One Kit | Component System |
|---|---|---|
| Installation complexity | Low — plug and play | High — requires wiring knowledge |
| Expandability | Limited to manufacturer's system | Fully customizable |
| Cost at small scale | Often better value under 5 kWh | Usually more expensive under 5 kWh |
| Cost at large scale | More expensive over 10 kWh | Better value over 10 kWh |
| Portability | Some models portable | Typically fixed installation |
| Support | Single manufacturer support | Multiple vendor relationships |
For most cabin and small off-grid applications, a quality all-in-one system from EcoFlow, Bluetti, or a Renogy complete kit is the right starting point. The engineering has been done for you, the components are matched, and support is simpler. Component systems make sense when your needs exceed what packaged kits can accommodate, or when you need specific customization for an unusual installation.
Where DIY Ends and Professional Work Begins
This is something most solar content sites gloss over, and it matters both practically and legally.
DIY is appropriate for: setting up a portable power station with panels, wiring DC components (panels, charge controller, battery bank) in a standalone system, and installing pre-engineered kit systems that don't connect to your home's electrical panel.
Professional work is required for: any system that connects to your home's AC electrical system, any system over 50V DC (which is most systems over a few panels), permits required in most jurisdictions for permanent installations, utility grid interconnection of any kind, and anything that touches your main electrical panel.
The permit and inspection requirement isn't something to work around. Off-grid solar installations that lack permits can create insurance issues and complications when you sell the property. A licensed electrician familiar with solar installations is the right resource for permanent systems.
Gas Backup for Off-Grid Systems
Quick Answer
Many off-grid installations add a fuel-powered generator as backup to the solar array for long cloudy stretches. A home standby generator such as a Generac Guardian is the wrong tool: Generac says its home standby units are designed to back up utility power and are not intended as the primary power source at sites without utility service, including off-grid cabins and solar systems, and that this use can compromise the warranty. A portable generator wired to your inverter-charger's generator input, or a prime-rated generator specified by a solar installer, is the better fit.
Most serious off-grid installations include a gas generator as a backup to the solar array. Not because solar fails - but because weather does. Three straight days of heavy cloud cover in January, a snow-covered panel array, or an unexpected battery bank maintenance day can all leave you without power at exactly the wrong moment. A backup generator that recharges the battery bank through your inverter-charger takes the worry out of watching the battery monitor drop.
The duty rating matters more than the brand. Generac states that its home standby generators are not designed to be the primary power source where there is no utility service, and it names off-grid cabins and backing up solar or wind systems as examples, so a Guardian-series unit does not belong here. For most cabins and small homesteads, a portable generator that you start when the batteries run low is the practical choice:
A portable gas generator rated at 5,500 running watts and 6,875 starting watts, with Generac's COsense carbon monoxide shutdown and electric start. Wire it to your inverter-charger's generator input so it recharges the battery bank during long cloudy stretches, and always run it outdoors, well away from doors and windows. It is a manually started backup, not an automatic standby system, so confirm your inverter-charger accepts generator input and check the current price before you buy.
For a larger homestead with heavy loads, ask a solar installer to specify a generator rated for prime or continuous duty and matched to your inverter-charger. See the generator comparison page for portable options.
Whole-Home Battery Storage and Solar Integration
For homeowners moving beyond portable power stations into permanent home energy storage, Greenworks makes two products worth considering as part of a full solar installation.
10kWh LiFePO4 battery storage, stackable to 80kWh. Works with new or existing solar. Includes SmartSwitch for grid-independent backup operation. The federal Section 25D residential clean energy credit ended for systems installed after December 31, 2025, so a 2026 installation does not qualify; check state and utility incentives with your tax professional. Requires professional installation.
7,600W output, accepts both AC and DC solar input, compatible with new and existing PV systems. Pairs with the PowerHub battery. Microgrid-capable for grid-independent operation. 12-year warranty. Requires a licensed solar installer.
Complete Your Setup
The add-ons most people wish they'd bought at the same time. Honest picks, matched to this setup.
Frequently Asked Questions
How many watts of solar do I need to live off-grid with a power station?
It depends on your daily watt-hours of use, not just wattage. Add up each device's watts times hours per day, then size panels to replace that, allowing for only four to six usable sun-hours and roughly 70 to 80 percent real-world efficiency. Most people undersize, so plan for more panel capacity than the raw math suggests.
Can a power station run continuously off solar without ever plugging into the grid?
Yes, if daily solar input meets or exceeds daily draw and the battery is large enough to bridge nights and low-sun days. The limiting factor is usually battery capacity and panel wattage during short winter days. Track it for a week with a watt meter before assuming it is truly self-sufficient.
What's the difference between a solar generator and a full off-grid solar system?
A solar generator, meaning a power station plus panels, is plug-and-play, portable, and needs no wiring, but has less capacity than a house-scale system with roof panels and a charge controller. It suits cabins, sheds, and partial loads, and expansion batteries let you scale up without an install.
How do I size an off-grid solar system?
Calculate your daily load in watt-hours (Wh) and add 25% for system losses. Size your battery bank to cover 2-3 days of that load. Size your solar array by dividing that loss-adjusted load by your location's winter peak sun hours. Add a charge controller sized for your panel array and an inverter sized for your maximum simultaneous load.
How many solar panels do I need to go off-grid?
It depends on your daily consumption. For a modest off-grid cabin using 3,000Wh per day, you need roughly 1,000-1,500W of solar panels to generate adequate power through seasonal variation. In cloudy climates or for winter use, size up by 50-100%.
What batteries are best for off-grid solar?
LiFePO4 (lithium iron phosphate) is the best choice for permanent off-grid installations. 3,000-6,000 cycle lifespan, safe chemistry, good temperature tolerance, and high depth of discharge. Lead-acid batteries are cheaper upfront but have shorter lifespans and lower usable capacity.
Can a portable power station work as an off-grid solar system?
For modest loads - lighting, phone charging, small appliances - yes. For full residential loads including heating, cooling, and cooking, no. Most single portable power stations hold about 1,000-4,000Wh. Some expandable home-backup models reach about 21kWh with add-on batteries (for example the Jackery HomePower 3600 Plus), but a full residential off-grid system typically needs 10,000-40,000Wh of permanently installed battery storage.
Do I need a gas generator for an off-grid solar system?
For serious off-grid installations, a fuel-powered generator is a common backup to the solar array. Not because solar fails, but because weather does. Three straight days of heavy cloud cover, a snow-covered panel array, or unexpected battery maintenance can leave you without power. Use a portable generator wired to your inverter-charger's generator input, or a generator rated for prime or continuous duty specified by a solar installer. Do not plan on a home standby generator: Generac says its home standby units are designed to back up utility power and are not intended as the primary power source at sites without utility service, including off-grid cabins and solar systems.
What size Generac generator do I need for off-grid backup?
Not a Generac home standby model. Generac says its home standby generators, such as the Guardian series, are designed to back up utility power and are not intended as the primary power source at sites without utility service, including off-grid cabins and solar systems, and that using them this way can compromise the warranty. For a cabin or small homestead, a portable generator such as the Generac GP5500 (5,500 running watts, 6,875 starting watts) wired to your inverter-charger's generator input covers winter shortfalls. For a larger homestead with well pumps and workshop loads, have a solar installer specify a generator rated for prime or continuous duty.