Best off-grid solar systems
How to choose an off-grid solar system for your home
Choosing an off-grid solar power system for your home is not easy, as off-grid systems are far more complicated than standard grid-connected solar systems. This article highlights the important factors that must be considered and describes the various off-grid systems available. We also explain why a good quality off-grid inverter is vital to building a reliable system. Finally, we will dive into the available batteries and determine which systems best suit different applications.
Many people believe off-grid solar systems can be easily put together. This may be true in the case of a small caravan or cabin, but larger off-grid systems used to power homes and businesses can cost tens of thousands of dollars and be problematic if designed incorrectly. This is why off-grid systems should be carefully sized by an experienced off-grid professional, taking into account the household loads, maximum demand, solar irradiance, and system losses.
The five main parts of an off-grid system
Unlike standard grid-connected solar systems, which generally consist of solar panels and an inverter, off-grid systems are far more complex and require more equipment, including batteries, off-grid inverters, solar charge controllers, and backup generators.
Solar panels
Off-grid Inverter
Solar inverter or Solar charge controllers
Battery bank
Generator (Optional)
Basic layout of a AC-coupled off-grid system - Well suited for modern off-grid homes and businesses with high AC loads
Key considerations when selecting an off-grid solar system
Off-grid systems must be sized accurately to meet the household's average and peak energy demands throughout the year and during adverse weather conditions. If the various loads and loss factors are not taken into account during the initial design process, this will result in poor performance, frequent power loss and even system failure. Learn more in our detailed guide to designing off-grid solar systems.
Key considerations when sizing off-grid solar power systems include:
Daily energy consumption (kWh) - Summer and winter average using a load calculator.
Peak loads (kW) - The maximum peak (surge) power demand.
Maximum demand (kW) - Inverter maximum continuous load (30-minute peak).
Solar exposure - Location, climate, panel orientation & shading issues.
Backup power options - Generator for periods of poor weather or faults.
With the above considerations in mind, a critical component of an off-grid power system is the off-grid inverter, often referred to as an inverter-charger. They are not just an inverter but a battery charger and must be able to meet peak loads and maximum demand. Learn more about the best off-grid inverters in our detailed review.
How much do off-grid solar systems cost?
The cost of a home off-grid system can vary substantially based on factors such as system size and complexity. For example, an off-grid setup designed to power a small home or cabin with essential appliances and lighting typically ranges from $20,000 to $30,000. This includes 6 to 8kW of solar panels, batteries, solar charge controllers, and a smaller capacity 4 to 5kW off-grid inverter. Mid-sized systems capable of powering small, efficient homes with more appliances and electric heating/cooling generally fall within the $30,000 to $60,000 range. These systems incorporate higher-capacity batteries, more powerful inverters and larger 10 to 15kW solar arrays. For off-grid systems supporting larger homes or multiple buildings, costs can easily exceed $60,000 and may extend into the six-figure range.
Small Cabin: $20,000 to $30,000 - 6 to 8kW Solar array, 12kWh battery & 4kW Inverter *
Average home: $30,000 to $60,000 - 8 to 15kW Solar array, 24kWh battery & 8kW Inverter *
Large home: $60,000 to $90,000+ - 20kW Solar array, 40kWh battery & 10kW Inverter *
Many different variables (*) can substantially vary the size and cost, including the geographical location (sunlight availability), building efficiency, consumption patterns (summer and winter loads), and the need for large backup generators or sophisticated monitoring. While the initial investment may seem significant, correctly sized off-grid solar systems using quality equipment can supply reliable power for many years and offer long-term savings by reducing backup generator runtime and maintenance. It's crucial for homeowners to conduct a detailed assessment, using a load calculator, with a solar professional to determine the most suitable system size and features based on individual needs and budget constraints.
Off-grid system types - AC or DC-coupled solar
Off-grid systems can a built using either AC or DC-coupled power sources. AC-coupled generation sources include common solar inverters and backup generators (gen-sets), while DC-coupled sources include solar charge controllers (MPPTs) or micro-hydro systems.
Whether a system is AC or DC-coupled is generally based on the size of the system. Most small-scale systems are DC-coupled and use low-cost, efficient MPPT solar charge controllers. Larger off-grid systems used for homes can be AC or DC-coupled depending on the type of off-grid inverter used and compatibility with different solar inverters. Most modern off-grid inverters can be both AC and DC-coupled, creating a very secure, flexible power system with multiple charging options. DC-coupling can provide black-start functionality, which enables easier system re-start if the main inverter shuts down, the backup generator fails, or the batteries are fully depleted.
Basic layout of a DC-coupled off-grid system - The most versatile and modular off-grid configuration
Small-scale DIY off-grid solar systems
Small-scale off-grid solar systems and DIY systems used on caravans, boats, small homes and cabins use MPPT solar charge controllers, also known as solar regulators, which are connected between the solar panel/s and battery. The job of the charge controller is to ensure the battery is charged correctly and, more importantly, not overcharged. Most small 12V/24V solar charge controllers also have load output terminals which are often used for simple DC lighting circuits. In small DIY systems, simple ‘plug-in’ style inverters provide 240V or 120V AC power. These are available in many different sizes, from tiny 150W inverters up to 3000W or higher.
Note: Small-scale, low-voltage systems can still cause damage or serious injury if not installed correctly - we recommend a trained, licensed solar or electrical professional installs all systems.
Small scale 24V off-grid system with a single MPPT solar charge controller and small battery inverter for AC loads.
Solar charge controllers have been around for decades and are available in two main types: PWM and MPPT. Learn more about solar charge controllers and how to size small-scale off-grid solar systems correctly. More powerful MPPT Solar charge controllers up to 100A are used on larger-scale off-grid solar power systems. These are a very efficient and reliable way of charging and managing high-capacity lithium or lead-acid battery systems.
Off-grid Battery Options
Lithium-Ion Batteries
Over the last few years, lithium-ion battery systems have become extremely popular due to their high round-trip efficiency (92% to 98%), compact size, lightweight, and scalability. In contrast, most lead-acid battery banks have a fixed size or capacity due to the battery cells (2V) being connected in series. On the other hand, most lithium systems are comprised of individual (24V or 48V) battery modules connected in parallel, so they do not suffer the same limitation. This flexible sizing allows additional batteries to be easily added at a later stage, as each lithium battery can operate independently and is not affected by the older lithium batteries. This modular feature is a real bonus for both installers and customers alike.
Another big advantage of lithium batteries is the ability to sustain a low (partial) state of charge for a prolonged amount of time without any negative effects, such as sulfation, which is a common problem with lead-acid batteries. Also, much higher charge rates can be achieved using lithium, with charging times up to 70% faster than lead-acid batteries. See our complete solar battery review for a detailed comparison of lithium batteries from the leading manufacturers.
The recommended self-managed lithium (Lithium Ferro Phosphate) batteries from the leading battery manufacturers include Simpliphi, GenZ, Discover AES, PowerPlus Energy and Zenaji Aeon.
Types of Lithium-Ion Batteries - LFP Vs NMC Vs LTO
Lithium-ion batteries have a much higher energy density than lead-acid batteries and are, therefore, lighter and more compact. However, there is not just one single type of lithium battery. Lithium-Ferro-Phosphate batteries are the most popular type of lithium battery chemistry used today, commonly referred to as Lithium-Iron, LFP or LiFePo4. These batteries have proven to be more thermally stable and safer and have a longer cycle life than most other Lithium battery types. The second most popular lithium chemistry used for storage batteries is NMC or Nickel-Manganese-Cobalt Oxide batteries, also called NMC batteries. These batteries are used in the Tesla Powerwall 2 and can be charged and discharged at a higher rate compared to LFP without reducing battery life. However, lithium NMC is not as thermally stable and needs to be kept in a more controlled environment, which is why the Powerwall 2 battery has a sophisticated liquid thermal management system. The third most popular type is Lithium Titanate or LTO. These batteries are claimed to have the longest lifespan and can be safely charged and discharged at extremely high rates. However, LTO batteries are very expensive and are not compatible with all off-grid inverters.
Advantages of Lithium Batteries
Very high round trip efficiency - 92% to 98%
Very high energy density - Compact and Lightweight
High charge and discharge rates allowed
No degradation issues with partial state of charge
Modular and scalable systems (upgradable)
Safe and low risk (if charged correctly), in particular LFP cells.
Most lithium batteries come with a 10 year warranty
Disadvantages of Lithium Batteries
Can shutdown at high temperatures (45+ degC)
Can shutdown at low temperatures (below 5 degC)
Can ‘trip off’ under continuous high surge loads.
More difficult to recycle at end-of-life.
May not function without a compatible inverter
Off-grid Lithium Battery Systems
Managed lithium batteries
The popular Pylontech US5000 (LFP) modular rack mount battery system uses CANbus communications to the inverter.
Managed lithium battery systems contain a BMS (battery management system) and require a dedicated communication link to the inverter. If the inverter isn’t compatible with the battery, they cannot function together and will not work. While generally very reliable, one potential issue with this type of system is that if communication is lost or suffers interference, the inverter or battery will shut down to ensure the battery is not overcharged or discharged. However, managed batteries offer the advantage of individual module-level monitoring, which is useful if one or more of the modules are underperforming or faulty. They also provide very precise battery level data and accurate SOC at all times.
The Pylontech US series and BYD LVL Premium series are popular managed lithium batteries used for grid-connected or off-grid systems, as they are compatible with a wide range of hybrid and off-grid inverters, including SMA, Selectronic, and Victron. See the complete list of managed lithium battery options here.
Self-managed lithium batteries
A 26.4kWh self-managed lithium LFP battery system from PowerPlus Energy. Each 3.3kWh module operates independently.
There are several self-managed lithium battery options available that also contain a BMS but do not require a communication connection (such as CANbus) with the inverter in order to operate. Most self-managed batteries are modular and able to be scaled to create very large capacity battery banks. Much like managed batteries, the internal BMS is used to monitor the state of charge (SOC), temperature and cell voltages. Another advantage of this type of battery system is it can be easily retrofitted and used to replace existing lead-acid battery banks since, much like lead-acid batteries, they do not require any special communications or connections. In the event of a system shut down or system black due to a low state of charge or low voltage, most self-managed batteries will restart automatically and do not require manual activation or reset to restart operation.
One disadvantage of self-managed battery systems is that the battery state of charge (SOC) needs to be monitored via an external DC shunt (current meter), which must be programmed and calibrated precisely to ensure the SOC value is correct according to the battery specifications. This generally works very well, but if the shunt is not installed or programmed correctly, accelerated battery degradation can occur, leading to low-voltage shutdown events and even premature battery failure.
Lead-acid batteries
Until around 6 years ago, lead-acid deep-cycle battery systems were the most common and reliable option for off-grid systems. Lead-acid batteries are a proven technology and can last 15 or more years if they are not held at elevated temperatures (above 40 deg C) and not regularly discharged too low. Lead-acid batteries require precise charging following a specific charge cycle and temperature sensors to adjust voltage settings. Most well-known off-grid inverters offer programmable charge voltage settings along with sensors to precisely charge under all conditions. Lead-acid deep-cycle batteries are still used and offer several advantages over lithium, as outlined below.
One of the most significant benefits of lead-acid batteries is that, unlike modern lithium batteries, they will not shut down at a low voltage or low state of charge (SOC). This is important, especially in emergencies or when a backup generator fails. Lead-acid batteries can be discharged down to 0% state of charge if needed for backup, but it is not recommended as it can severely reduce the battery's life.
Advantages
Compatibility with most inverters.
Proven and trusted technology.
Safe, very low risk (sealed Gel/AGM).
The battery will not cut out at low SOC or low voltage**
Long life (if not over-discharged)
Easily recycled
Disadvantages
Low round-trip efficiency - 75% to 80%
Low energy density - Very heavy
Usable capacity limited - Max 40% DoD on a regular basis
Not modular - Fixed-size once installed
Cannot sustain a partial state of charge for long periods
High temperatures can drastically reduce battery life
** Cutout voltage & SOC based on inverter settings and rate of discharge.
In specific applications, high-performance lead-acid batteries are still an excellent choice for off-grid systems. Lead-acid is a well-proven and reliable technology that is compatible with virtually all off-grid inverters and solar charge controllers. Lead-acid battery banks can also be more reliable in some situations as the battery will not automatically shut down in extreme temperatures or when a low state of charge is reached. In addition, they can be easily recycled using existing infrastructure.
Best Off-grid Inverters
Off-grid inverters used to power modern off-grid homes are powerful battery inverters capable of supplying pure sine wave AC power to all loads and appliances under all conditions. These inverters also contain powerful built-in chargers, which is why they are often referred to as inverter chargers. Off-grid inverters are available in a wide range of sizes from 2.4kW up to 20kW and generally contain large, heavy transformers that can power appliances with high-surge loads, including pumps, compressors and other air-conditioning units.
Power off-grid inverters - SMA Sunny Island, Schneider Electric XW+, Selectronic SP PRO, Victron Quattro, and Outback Power Radian series.
Modern off-grid inverters, often called multi-mode inverters due to their ability to operate in various modes, are the heart and brains of any off-grid system and manage multiple power sources simultaneously, including solar (AC or DC-coupled), backup generators and can even be grid-tied and operate in hybrid mode. Off-grid inverters must be sized correctly according to the loads and appliances they will be running. Many cheap battery inverters cannot handle high continuous or surge loads, leading to system failure or tripping events. See our best off-grid inverter review for the highest quality and best-performing off-grid inverters.
Technical Guide to selecting off-grid inverters
For a detailed guide to selecting and sizing an off-grid inverter, see our Technical guide to choosing off-grid and energy storage systems. An experienced solar professional should provide a load table to help determine which type and size inverter will best suit your needs. A load table or a load calculator is also required to help accurately size the solar array, battery and backup generator.
Best off-grid Solar Systems Summary
This summary highlights the top-performing off-grid solar systems available across different regions. While most systems allow for the interchangeability of many components, it's crucial to note that not all inverters, MPPTs, and batteries are compatible. The systems featured below are some of the most popular and have a proven track record of reliability based on many years of use and low failure rates, yet there are other reputable off-grid inverters and battery options in the market. Before making any off-grid equipment purchases, we advise reading this article along with our related articles. Additionally, we strongly recommend engaging an experienced off-grid solar professional for design and installation.
1. Best value off-grid solar system
Small to medium size homes * (Available Internationally)
2. Best mid-size off-grid solar system
Medium-size homes * (Available in Australia)
Off-grid Inverter: Selectronic SP PRO SPMC482 (7.5kW) Inverter
Charge Controller: Fronius Solar Inverter & AERL MPPT charge controllers
Battery System: PowerPlus Energy ECO or Premium Battery system
Backup Power: Auto-start diesel generator 12kVA
3. Best off-grid solar system North America
Medium-size homes * (Available in the USA)
Off-grid Inverter: Outback Power Radian GS8048 (8kVA) Inverter
Charge Controller: Outback MPPT solar charge controllers
Battery System: Discover AES Rack-mount Battery
Backup Power: Auto-start diesel/propane generator 12kVA
(*) This is a basic guide only. The selection and sizing of off-grid inverters and equipment must be done based on the household's average and peak energy demands (load calculations).
