DIY solar system: How to plan and build your own

Updated 2026-10-25

A DIY solar system is one you plan, buy and install yourself: solar panels, a charge controller, a battery bank and an inverter, wired together to power a cabin, shed, RV, workshop or part of your home. Building one comes down to seven steps. Work out how much power you use, then choose panels, size a battery bank, pick a charge controller and an inverter, wire it all safely, and mount the panels where they get full sun.

This guide walks through each step in order and explains the choices that matter at each one. It also covers grid-tied versus off-grid systems, whether to buy a kit or build from parts, how to estimate the cost, and where you’ll need permits or a licensed electrician.

Contents

• What’s in a DIY solar system
• Grid-tied, off-grid or hybrid
• Step 1: Work out your power needs
• Step 2: Choose your panels
• Step 3: Size your battery bank
• Step 4: Pick a charge controller
• Step 5: Choose an inverter
• Step 6: Wire the system
• Step 7: Mount and install
• Going fully off grid
• Kit or build from parts?
• What a DIY system costs
• Safety, permits and when to hire an electrician
• Frequently asked questions

What’s in a DIY solar system

Most DIY systems, from a small shed setup to a full off-grid cabin, use the same core parts:

• Solar panels turn sunlight into direct current (DC) electricity. Together, the panels are called the array.
• A charge controller sits between the panels and the batteries. It regulates the panels’ voltage and current so the batteries charge fully without being overcharged.
• A battery bank stores energy for nighttime, cloudy days and loads bigger than the panels can supply at that moment.
• An inverter converts the batteries’ DC power into the alternating current (AC) that household outlets and most appliances use.
• Wiring and protection: cables sized for the current they carry, fuses or breakers, a disconnect switch and grounding.
• Mounting: racks or brackets that hold the panels on a roof, on the ground or on a pole.

Power flows through those parts in one direction:

Solar panels → charge controller → battery bank → inverter → AC loads
   (DC)           (regulated DC)       (DC)          (AC)

Some products combine parts. An all-in-one inverter-charger, for example, includes the charge controller and inverter in one box. A grid-tied system without batteries skips the charge controller and battery bank, and its inverter feeds power straight into your home’s electrical panel.

Grid-tied, off-grid or hybrid

The first decision is whether your system connects to the utility grid:

• Grid-tied systems connect to your home’s electrical panel and the utility grid. They have no batteries. They run your home during the day, send any surplus to the grid, and draw from the grid at night. They are the cheapest way to cut a power bill, but they shut down during a grid outage for the safety of utility workers.
• Off-grid systems aren’t connected to the grid at all. Everything you use has to come from the panels and batteries, so they need a bigger battery bank and careful sizing. They suit cabins, remote properties, RVs and outbuildings where running a utility line is impractical.
• Hybrid systems connect to the grid and also have batteries. They can keep chosen circuits running during an outage and store solar power for the evening.

Most first DIY builds are small off-grid systems, because they don’t need utility approval and you can start small and expand. Grid-tied and hybrid systems connect to the utility’s wiring, so they come with permits, inspections and an interconnection agreement (see the safety section below).

Step 1: Work out your power needs

Every other choice follows from one number: how many watt-hours (Wh) you use in a day.

Make a load list. For each device you want to run, multiply its power in watts by the hours a day you’ll run it, then add up the results:

These figures are hypothetical. Check each device’s label or datasheet for its wattage, or measure it with a plug-in watt meter. For appliances that cycle on and off, like fridges, use the average daily draw instead of the peak. Round your total up and add 10 to 20% for things you forgot. In this example, that gives about 2,000 to 2,400 Wh a day.

For a whole home, skip the load list and use your electric bill. Our guide to how many solar panels you need for your home shows how to work from yearly kWh instead.

Step 2: Choose your panels

Once you know your daily use, you can size the array:

Array size (W) = daily use (Wh) ÷ (peak sun hours × loss factor)

Peak sun hours describe how much sunlight your location gets, and the loss factor (about 0.75 to 0.85) accounts for heat, dust, wiring and conversion losses. Our guide to how much power a solar panel produces explains both terms. With 2,000 Wh a day, 4.5 peak sun hours and a loss factor of 0.8, you need about 2,000 ÷ (4.5 × 0.8) ≈ 556 W. Round up to 600 W, for example three 200 W panels.

Then choose the panel type:

• Monocrystalline vs polycrystalline. Monocrystalline panels are more efficient, so you need less space for the same wattage, and they are now the standard for new panels. Polycrystalline panels are less common and mainly worth it as a cheap used find.
• Rigid vs flexible. Rigid framed panels last longest and suit roofs, ground mounts and poles. Flexible panels are light and can bend to curved surfaces like RV and boat roofs, but they usually run hotter and wear out sooner.
• Panel wattage and size. Larger panels (300 W and up) cost less per watt and mean fewer mounts and connections, but they’re heavy and awkward to lift onto a roof. Smaller 100 to 200 W panels are easier to handle and fit small roofs.

Check that each panel’s voltage suits the charge controller you plan to use (Step 4) before you buy.

Step 3: Size your battery bank

The battery bank has to cover your nighttime use and carry you through cloudy days. The sizing formula is:

Battery capacity (Wh) = daily use (Wh) × days of autonomy ÷ usable depth of discharge

• Days of autonomy is how many days the batteries should last with little or no sun. One to two days is common for a weekend cabin, and three or more for full-time off-grid living.
• Usable depth of discharge is how much of the battery’s rated capacity you can use without shortening its life. It’s around 80 to 100% for lithium iron phosphate (LiFePO4) batteries and around 50% for lead-acid.

With 2,000 Wh a day, two days of autonomy and LiFePO4 batteries at 90%, you need about 2,000 × 2 ÷ 0.9 ≈ 4,400 Wh. Battery capacity is often listed in amp-hours (Ah), so divide by the system voltage: 4,400 Wh ÷ 24 V ≈ 185 Ah at 24 V.

Most new DIY builds use LiFePO4 batteries. They cost more upfront than lead-acid, but they last many more charge cycles, weigh less and need no maintenance. Lead-acid batteries can still make sense for a small system on a tight budget. Our battery guide compares the main battery types and shows how to size your solar battery bank and wire it safely.

Step 4: Pick a charge controller

The charge controller protects the batteries and gets the most out of the panels. There are two types:

• PWM (pulse-width modulation) controllers are simple and cheap. They work well for small systems where the panel voltage closely matches the battery voltage, such as one 12 V panel charging one 12 V battery.
• MPPT (maximum power point tracking) controllers convert the panels’ higher voltage into extra charging current. They harvest more energy, especially in cold weather or when the panel voltage is well above the battery voltage. They’re the usual choice for any system beyond a few hundred watts.

Size the controller on two numbers:

1. Current: array watts ÷ battery voltage × 1.25 for a safety margin. A 600 W array on a 24 V battery needs about 600 ÷ 24 × 1.25 ≈ 31 A, so you’d choose a 40 A controller. On a 12 V battery, the same array needs about 63 A.
2. Input voltage: the array’s open-circuit voltage, which rises in cold weather, must stay below the controller’s maximum PV input voltage. Check the panel datasheets and allow a margin for your coldest mornings.

Both numbers depend on how you wire the panels (Step 6), so plan the wiring and the controller together. Our guide to choosing and sizing a solar charge controller works through a full example, including the cold-weather voltage check and the settings to get right.

Step 5: Choose an inverter

The inverter has to handle everything you run at the same time, plus the brief surge some appliances draw when they start:

• Continuous rating: add up the watts of everything that might run at once and pick an inverter rated comfortably above that total. In the example load list, the fridge, pump, laptop and lights together draw about 410 W, so a 1,000 W inverter leaves room to grow.
• Surge rating: motors in fridges, pumps and power tools can draw several times their running watts for a moment when they start. Check the inverter’s surge rating against your largest motor.
• Pure sine wave: choose a pure sine wave inverter. Cheaper modified sine wave units can make motors run hot and buzz, and some electronics won’t work on them.
• Input voltage: the inverter’s DC input has to match the battery bank’s voltage.

Bigger systems favor higher battery voltages. A 3,000 W inverter on a 12 V bank draws about 250 A, which needs very thick cable, while the same inverter on a 48 V bank draws about 63 A. A rough guide: 12 V for systems up to about 1,000 W, 24 V up to about 3,000 W, and 48 V above that. Our guide to what size off-grid inverter you need has a worked example with running and surge watts.

Step 6: Wire the system

Wiring turns separate parts into a safe working system. The main choices are:

• Series vs parallel. Wiring panels in series adds up their voltages while the current stays the same. Wiring them in parallel adds up their currents while the voltage stays the same. Series wiring reduces current, so you can use thinner cable for long runs, but shade on one panel drags down the whole string. Many systems combine the two (series-parallel).
• Wire gauge. Size each cable for the current it carries and the length of the run, keeping voltage drop to a few percent. Low-voltage DC systems carry high currents, so the cable between the batteries and the inverter is usually the thickest in the system.
• Fuses and breakers. Put overcurrent protection on every circuit that a battery or a parallel group of panels could feed, including a fuse close to the positive battery terminal. Add a disconnect so you can isolate the panels and batteries for maintenance.
• Grounding. Ground the panel frames and racking, and follow the equipment’s instructions for grounding the system.

Use connectors and cable rated for outdoor solar use, and follow each component’s installation manual, since the manufacturer’s specified wire sizes and fuse ratings take priority. Our guide to wiring solar panels in series vs parallel walks through each layout step by step, with a worked example.

Step 7: Mount and install

The panels need full sun, ideally from midmorning to midafternoon, with no shade from trees, chimneys or other buildings:

• Roof mounts use space you already have and keep cable runs short. They need a sound roof, flashing to keep out water, and fixings into the rafters, not just the roof deck.
• Ground mounts are easier to install, clean and adjust, and they don’t touch the roof. They need open space and a cable run back to the batteries.
• Pole mounts lift a few panels above snow and shade, and some can tilt or track the sun.

In the Northern Hemisphere, face the panels south. A fixed tilt close to your latitude works well year-round. Tilt them steeper to favor winter and flatter to favor summer.

Put the batteries, charge controller and inverter close together, in a dry space that stays within the batteries’ temperature range. Keep the cable runs between them short. Our step-by-step guide to how to install solar panels covers the racking, flashing, panel clamps and connection order in detail.

Going fully off grid

Powering a home completely off grid uses the same seven steps on a bigger scale, and it leaves less room for error. Size for the worst month of the year, usually December or January, instead of the yearly average. Plan for more days of autonomy, and add a backup generator for long cloudy stretches. Cutting your daily use is the cheapest upgrade there is. Efficient appliances and running a propane or wood stove for heat and cooking can shrink the system you need considerably. Our guide to planning an off-grid solar system covers winter sizing, backup power and a worked example for a full-time home.

Kit or build from parts?

A solar panel kit bundles matched parts in one box. Building from parts means choosing each component yourself.

A kit is the easier route for a first system, as long as its capacity matches your load list. Our roundup of the best solar panel kits compares kits by wattage, battery and inverter. Building from parts makes more sense once you know exactly what you need, or when no kit fits.

What a DIY system costs

Cost depends on the size of each part, so the best estimate comes from your own numbers. Price the panels by their watts, the batteries by their usable Wh, and the charge controller and inverter by their ratings. Then add 10 to 20% for wiring, fuses, mounts and other parts that are easy to forget. Battery storage is often the biggest single cost in an off-grid build.

For a home-sized system, our solar panel cost calculator walks through the estimate step by step, from system size and price per watt to incentives and payback.

Safety, permits and when to hire an electrician

Solar systems carry enough power to cause fires and serious shocks, and the DC side can’t be switched off just by flipping a breaker, because the panels produce power whenever light hits them.

• Electrical code. In the US, solar installations fall under the National Electrical Code (NEC), mainly Article 690 for PV systems and Article 706 for energy storage. Rooftop systems on homes also have to meet rapid shutdown rules. Your local building department decides which code edition applies.
• Permits. Many areas require a permit and an inspection for any solar installation attached to a building or wired into one, and some require one even for off-grid systems. Check with your local building department before you buy.
• Grid-tied systems need utility approval. Connecting a system to the grid usually requires a licensed electrician, a permit, an inspection and an interconnection agreement with your utility. The utility then gives you permission to turn the system on. You can do much of the planning and physical work yourself, but plan on a licensed electrician making the final connection to your home’s electrical panel.
• Battery safety. Fuse the battery bank, use a battery management system (BMS) with lithium batteries, ventilate lead-acid batteries, which can release hydrogen gas while charging, and keep batteries within their rated temperature range.
• Roof work. Use fall protection on any roof, and leave steep or high roofs to professionals.

If you’re unsure about any part of the wiring, have an electrician review the design before you buy parts and inspect the system before you switch it on.

Frequently asked questions

Can I build my own solar system?

Yes. Small off-grid systems for sheds, cabins, RVs and backup power are common DIY projects, and the parts are widely sold. Grid-tied systems are also possible, but they usually need a permit, an inspection, utility approval and a licensed electrician for the final hookup.

Is DIY solar cheaper?

Usually, yes. Doing the work yourself avoids the installer’s labor and overhead, which make up a large share of a professional install’s price. You give up the installer’s design work and workmanship warranty, though, and you’re responsible for permits and for getting the system to pass inspection.

How big a solar system do I need?

Divide your daily use in watt-hours by your peak sun hours times a loss factor of about 0.8. Steps 1 and 2 above show the method, with a worked example.

What voltage should a DIY solar system be?

It depends on the inverter size. A 12 V system suits small builds up to about 1,000 W, 24 V suits mid-sized systems, and 48 V is usual above about 3,000 W because it keeps currents and cable sizes down.