Ethan BrooksBy Ethan Brooks

Updated November 2026

A complete 5kW solar power system off grid for home is sized to run most of a typical house without a utility connection, provided you design the battery bank and load profile around it. In this guide you will learn how to estimate your daily energy use, size the solar array, battery storage, inverter, and charge controller, and lay out the wiring in a safe, code-aware order. The math is straightforward once you have your numbers, and the checklists below will keep you from skipping the steps that cause most failed installations.

What a 5kW Off-Grid System Can and Cannot Power

The “5kW” rating refers to the inverter’s continuous AC output and, in most designs, the approximate size of the PV array in watts of panels. A 5kW inverter can supply 5,000 watts of continuous load, with short surges higher depending on the model. Manufacturers typically list surge ratings for motor starts, so check the datasheet for the figure that applies to your refrigerator or well pump.

In practical terms, a well-designed 5kW off-grid home system can handle lighting, refrigeration, a well pump, internet equipment, a washing machine, and a microwave, but not all of them at once and not an electric range plus a heat pump simultaneously. Plan around your average daily kilowatt-hours (kWh), not just the peak wattage.

Step 1: Calculate Your Daily Energy Use

Start with an inventory of every appliance you plan to run from solar. For each item, record its wattage, how many hours per day it runs, and how many days per week it runs. Multiply watts by hours to get watt-hours per day, then sum the list.

  1. List each load and its rated wattage from the nameplate or manual.
  2. Estimate daily run time. A refrigerator typically cycles, so use a duty-cycle estimate (often 8 to 10 hours of actual compressor run time per day for a modern unit) rather than 24 hours.
  3. Multiply watts by hours to get Wh/day for each load.
  4. Add all loads to get your total daily Wh.
  5. Add 20 to 25 percent for inverter and wiring losses, and for future growth.

A household that uses roughly 15 kWh per day after losses is a reasonable target for a 5kW system with a properly sized battery bank. If your number is much higher, reduce loads or plan for a larger system. Unsure about your load calculations? Consult a licensed electrician or a qualified solar installer before committing to a design.

Step 2: Size the Solar Array

Once you know daily energy use, size the PV array to replace it on a typical sunny day, accounting for your site’s peak sun hours. Peak sun hours are the equivalent hours per day at 1,000 W/m² irradiance and vary widely by region and season. Use the lowest month you need to cover, not the annual average, if you want reliable winter operation.

Formula: Array watts = Daily Wh ÷ (Peak sun hours × system efficiency). A system efficiency of 0.75 is a common planning value that covers temperature derating, wiring, and charge controller losses.

For example, if your daily load is 12,000 Wh and your winter peak sun hours are 3.5, the array needs to be about 12,000 ÷ (3.5 × 0.75) ≈ 4,571 W, or roughly 4.6kW of panels. A 5kW system gives you a small margin. Panel selection and mounting are covered in depth in our guide How to Install Off Grid Solar Power System: A Step-by-Step Guide for Beginners.

Step 3: Size the Battery Bank

Batteries are where off-grid systems most often fail. Size them to hold a specified number of days of autonomy, usually one to two days for a home that can tolerate a backup generator.

Formula: Battery usable Wh = Daily Wh × Days of autonomy ÷ Depth of discharge. Lithium iron phosphate (LiFePO4) batteries are commonly rated for a depth of discharge of 80 to 90 percent, while lead-acid batteries are usually limited to about 50 percent to preserve lifespan.

Battery type Typical usable depth of discharge Notes
LiFePO4 (lithium iron phosphate) 80 to 90 percent Higher efficiency, lighter, longer cycle life; needs a BMS compatible with your inverter
Flooded lead-acid About 50 percent Lower upfront complexity, requires water maintenance and ventilation
AGM or gel lead-acid About 50 percent Sealed, no watering, but more sensitive to overcharge

Using the 12,000 Wh example with two days of autonomy and LiFePO4 at 90 percent depth of discharge: 12,000 × 2 ÷ 0.9 ≈ 26,700 Wh of nominal capacity. For a 48V bank, that is roughly 555 Ah. Many homes use a 48V architecture because it reduces current and wire size for a 5kW inverter.

Step 4: Choose the Inverter and Charge Controller

A 5kW off-grid inverter-charger is the heart of the system. Look for a unit that provides a split-phase 120/240V output if your home is wired that way, a transfer switch for a generator input, and a built-in or external MPPT charge controller. Confirm the inverter’s maximum PV input voltage and the number of strings your array requires.

MPPT charge controllers extract more energy from the array than PWM controllers, especially when the panel voltage is higher than the battery voltage. Size the controller so the array’s short-circuit current stays within its rating, and so the open-circuit voltage at your coldest expected temperature remains below the maximum input. Our article Off Grid DC Solar Power System: A Step-by-Step Sizing and Wiring Guide walks through those voltage checks.

Step 5: Plan the Wiring and Protection

Off-grid wiring follows a logical order: panels to charge controller, controller to battery, battery to inverter, inverter to the main panel. Each DC segment needs fusing or a breaker close to the battery, and a disconnect at each source.

  1. Mount panels and run PV conductors to a combiner box with string fuses or breakers.
  2. Route PV wiring to the charge controller, sized for the controller’s current rating and temperature.
  3. Install a DC disconnect and fuse between the battery and inverter, sized close to the battery terminal.
  4. Connect the inverter AC output to a sub-panel or transfer switch feeding your critical loads.
  5. Bond the system to a grounding electrode per your local code, and install surge protection on the PV side.

Battery cable sizing matters more than most beginners expect. At 48V and 5kW, current can exceed 100 amps at the inverter, so use cable and lugs rated for that load with short runs.

Tools and Materials Checklist

  • Clamp meter and multimeter rated for DC solar voltages
  • Torque wrench for battery and busbar lugs
  • Crimping tool rated for the conductor size you use
  • Insulated tools and appropriate PPE
  • Labels for all disconnects and breakers
  • Permit documents and a copy of your local electrical code

Common Mistakes

  • Sizing the array for average sunlight instead of the worst month you need to cover.
  • Forgetting inverter standby draw and battery self-discharge in the daily energy budget.
  • Ignoring open-circuit voltage at cold temperatures, which can exceed controller limits.
  • Using undersized battery cable, causing voltage drop and heat at the lugs.
  • Skipping a generator or other backup for long cloudy periods.
  • Mixing battery chemistries or ages in the same bank.

Tips for a Smoother Build

  • Build the load list first, then design the system. Changing loads later is expensive.
  • Choose a 48V system if your inverter supports it, for lower current and easier wiring.
  • Plan for expansion by leaving space in the battery rack and combiner box.
  • Keep a logbook of battery voltage, state of charge, and generator run hours during the first months.

A clamp meter lets you check DC current on live conductors safely, which is essential during commissioning. View on Amazon

A torque wrench ensures battery and busbar lugs are tightened to specification, preventing loose connections that cause heat. View on Amazon

A crimping tool matched to your cable gauge produces reliable, low-resistance terminations on heavy battery cable. View on Amazon

FAQ

Can a 5kW off-grid system run an entire house?

It can run most essential loads, but not every appliance at once. Electric ranges, dryers, and central air conditioning often exceed what a 5kW inverter can supply continuously. Many owners pair solar with a propane range and a high-efficiency heat pump.

How many batteries do I need for a 5kW system?

It depends on daily energy use and days of autonomy. A typical home using about 12 kWh per day with two days of storage needs roughly 25 to 27 kWh of usable LiFePO4 capacity, which may be configured as several modules in parallel.

Is 48V better than 24V or 12V for a 5kW system?

Higher voltage reduces current for the same power, which allows smaller wire and lower losses. A 48V architecture is the common choice for systems at this size.

Do I need a generator with an off-grid solar system?

Most designs benefit from a backup generator for extended cloudy periods, especially in winter. A transfer switch and automatic start can make the switchover seamless.

How many solar panels does a 5kW system use?

Using modern panels rated around 400 to 450 watts each, a 5kW array typically uses about 11 to 13 panels. The exact count depends on the panel wattage and your array sizing calculation.

Can I install the system myself?

Many people do, but DC and battery work carries real shock and fire risk. Permits and inspections are often required, and a licensed electrician or qualified solar installer should review the design and final connections.

How long do off-grid batteries last?

LiFePO4 batteries are commonly rated for several thousand cycles at moderate depth of discharge. Lead-acid batteries generally last fewer cycles and need more maintenance. Check the manufacturer’s warranty and cycle rating before you buy.

Where should I read more about off-grid system options?

If you are comparing ready-made packages, see 7 Best 5kW Off Grid Solar Power System Options for Homes (2026). For a sizing walk-through, Off-Grid Solar Power System Calculator: How to Size Your Setup Step-by-Step covers the math in more depth.

Conclusion

A complete 5kW solar power system off grid for home depends on accurate load data, a conservative battery design, and careful wiring and protection. Work through the load calculation first, then size the array, batteries, inverter, and controller in that order. Verify your design against local code and have a licensed professional review the final installation before energizing the system.

Ready to choose one?

Ethan Brooks

About Ethan Brooks

Ethan Brooks is part of our editorial team and reviews and edits our DIY solar power systems guides, checking product details against manufacturer specifications and owner feedback.