How to Design an Off Grid Solar Power System? (2023)

Nowadays, there are still a large number of people living in impoverished or remote areas, which are far away from power plants and public power grids. Due to shortage of power or even without power, they cannot enjoy the information and convenience brought by modern civilization. The off-grid solar power system is an independent self-sufficient renewable energy power supply system, which can resolve their basic power use demands.

A typical off-grid solar PV system is made up of six parts, including solar panels, the holder, solar charge controller, off-grid inverter, batteries, and distribution box. The solar cells are connected to the solar charge controller, it produces the energy to first satisfy user’s daily use, and then the superfluous power is stored in the batteries for use at night and during overcast and rainy days. When the power in the batteries is used up, a majority of inverters can support the input of mains supply (or the diesel generator) as the supplementary energy source for the load.

The off-grid solar power system design is different from the grid-tie solar power system. The former needs to take into considerations many factors including the load, daily electricity quantity and local climate conditions and so on, to choose different design plans according to clients’ practical demands. Therefore, the off-grid solar photovoltaic system is comparatively complex.

Get to know how much power of your load

In order to ensure reliability of the off-grid PV system, a thorough survey of customer demands for the electricity is very necessary. That is, you should figure out how much power you need, including the power ratings of all the appliances or devices, running time and the daily electricity consumption (i.e. How many kilowatt-hours is it in total). After that, the design of the off-grid solar power system are mainly based on these data, including the solar inverter selection, solar panel capacity calculation, and batteries capacity calculation.

Solar inverter selection

(Video) How to design an off grid solar power system

The power rating ofsolar inverterto be selected should not be smaller than the total power of the loads. However, considering the lifespan and follow-up capacity expansion of the inverter, certain margin of safety should be left for the inverter power, which is generally 1.2 to 1.5 folds as much as that of the load power.

Besides, if the load includes the sensitive appliances, such as the refrigerator, air-conditioner, water pump, and smoke exhaust ventilator with electric motor (the startup power of the electric motor is 3 to 5 folds of its rated power), then the startup power of these load should also be taken into account. In other words, the startup power of these load should be smaller than the maximum surge power of the inverter.

Below is the formula for the solar inverter’s power selection, which is just for reference upon design.

Power of inverter = (Power of load * Margin factor)/ Power factor of inverter

Solar panel capacitycalcultation

The power generated by solar panel modules in the daytime is partly for the load use, and the remaining is for charging the storage battery. When the night comes or when the solar radiation is inadequate, the electricity in the storage batteries will be discharged for the load use. Thus, it can be seen that the all the electricity consumed by the load is from the electricity generated by photovoltaic modules in the daytime, when there is no mains supply or when the diesel engine serves as the supplementary energy source. Considering differences of illumination intensity in different seasons and in different regions, the capacity design of the solar panel should be capable of meeting demands even in worst season of sunshine lighting so as to ensure the solar system’s reliable operation. Below is the formula for computing of the solar panel capacity:

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Power of solar panel = (Load daily eletricity consumption * Margin factor)/ (Peak sunshine hours of worst month*Efficiency of the system)

Batteries capacity calcultation

The batteries of the off-grid solar power system is mainly used to store energy and ensure that the load can work normally when the solar radiation is insufficient. In terms of the off-grid solar photovoltaic system for important equipment, the design of the batteries capacity should take the number of local longest overcast and rainy days into consideration. The ordinary off-grid solar system does not have such high requirement of power supply to the load and considering the cost of the system, the number of overcast and rainy days can be left unconsidered, and the load use can be adjusted according to the actual illumination intensity.

In addition, most off-grid solar PV systems adopt lead-acid batteries, whose depth of discharge generally ranges from 0.5 to 0.7. The batteries’ capacity to be choose can refer to the following formula:

Batteries' capacity = (Daily electricity consumption× Number of successive rainy and overcast days) / Batteries’ depth of discharge

Solar charge controller selection

(Video) Loads List: Off Grid Solar Power System Design - Step 1

Solar charge controlleris a device that manages the charging and discharging the power from the solar panel to the batteries. The two key factors to select a suitable charge controller are rated voltage and current. The rated voltage of charge controller in line with the operating voltage of the batteries in the solar system. As for the current rating, it can be roughly calculated by the power from the solar panel divided by the voltage of batteries, and also reserve a margin of 25% for safety consideration.

In addition, there are two type of solar charge controller in the market, PWM and MPPT. Generally, PWM solar charge controller is priced lower than MPPT and more suitable for small solar power inverter system. However, MPPT solar charge controller is more cost effective due to its unique advantages over the others. It can be selected based on specific design plan.

A typical design plan for 10kVA off-grid solar power system

Project background: To design an off-grid solar system for a school to satisfy its daily power consumption.

1. Survey on electricity demand

A survey of customer demands should be carried out in the early stage of design plan. The information on load power consumption should be accurate. Below are more details:

(Video) Workshop: Off-grid System Design

How to Design an Off Grid Solar Power System? (1)

2. Choosing solar inverter

Client’s load mainly includes the classroom lighting, classroom fans, lighting of public places, wall lighting, broadcasting system, etc. The total load power is 6.84%kW and the solar inverter power should be no smaller than 9.8kVA. According to these requirements, the 10kVA solar inverter with MPPT charge controller can be selected, which plays a role of inverter and charge controller in one unit.

3. Calculating solar panel capacity

According to the client demand survey, it can be seen that the school’s average daily electricity consumption is around 61.5kWh. The local illumination conditions are favorable, it can calculate the daily duration of sunshine by 4.23h. The solar panel is configured with 1.1 fold of allowance. In this design, 88 pieces of 270W polycrystal photovoltaic modules are adopted with a total power of 23.76W and the average daily power generation of 100.5kWh. The system efficiency is generally around 0.8, so the daily electricity consumption is 80kWH.

4. Calculating batteries capacity

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The school’s lighting is usually during the night. Considering the batteries’ service life, the battery capacity should be properly increased, and the battery backup time is two days as required by the client. The depth of discharge of the battery is set to 0.7. This project adopts the 110-node 1000AH/2V gel batteries in series, whose total capacity is around 220,000VAH, and the utilizable electricity quantity is around 154kWH, which can satisfy the power demand of two day backup time.


How do you design a solar power system? ›

  1. Determine power consumption demands. The first step in designing a solar PV system is to find out the total power and energy consumption of all loads that need to be supplied by the solar PV system as follows: ...
  2. Size the PV modules. ...
  3. Inverter sizing. ...
  4. Battery sizing. ...
  5. Solar charge controller sizing.

How big of a solar system do I need to go off-grid? ›

The average off-grid home usually requires about 7 Kw (or 7000 Watts) of power to rely entirely on its own energy production. Solar panels come in various forms, shapes and sizes.

What are the 4 main components for an off-grid solar electric system? ›

For most DC-coupled off-grid systems it really comes down to four main components – solar panels, charger controller, inverter and the battery bank. There is a lot more that can go into a solar system setup, but those are the four main pieces that will be discussed in this article.

How do I calculate what size solar system I need? ›

You can calculate how many solar panels you need by multiplying your household's hourly energy requirement by the peak sunlight hours for your area and dividing that by a panel's wattage. Use a low-wattage (150 W) and high-wattage (370 W) example to establish a range (ex: 17-42 panels to generate 11,000 kWh/year).

How much solar and battery do I need to go off-grid? ›

If you want to keep the power on when the grid is down, you'll usually just need one solar battery. If you want to go off-grid completely, you'll need far more storage capacity, more along the lines of 8-12 batteries.

How many deep cycle batteries does it take to power a house? ›

A 400 amp-hour 6 volt battery can provide around 2.4 kilowatt hours of power. A three-day battery bank planned to provide 90 kilowatt-hours of electricity to an average American household. The previous example battery can provide2,4 kilowatt hours, while 38 batteries would be needed.

Can a house run on solar power alone? ›

With a modern solar energy system, including power storage, you can definitely run a whole house completely on solar power. Today's high-efficiency solar panels and solar batteries make it cheaper than ever before to power an entire home exclusively using solar energy.

How many amps will a solar panel produce? ›

Solar panels produce between 250 and 400 watts, and wattage is equal to the voltage multiplied by amps. As voltage varies, solar panels produce between 14 and 24 amps, enough to power small appliances.

Can I install my own off-grid solar system? ›

DIY Off Grid Solar Kits have become a lot more popular and If you're looking to install solar panels for a smaller building, such as a holiday shack or shed, it is possible to set up your own stand alone system.

Do On grid solar systems need batteries? ›

On-grid or grid-tie solar systems are by far the most common and widely used by homes and businesses. These systems do not need batteries and use either solar inverters or micro-inverters and are connected to the public electricity grid.

How much does 10kW off-grid solar system cost? ›

A 10kW solar panel system typically costs between $9,500 – $12,500. Prices vary for 10kW systems according to your location and, the quality of components and company you select to perform the install. Solar rebates vary according to the size of your system and the sunshine hours your postcode receives.

How many batteries are needed to power a house? ›

Number of Batteries

A battery bank designed to power an average American household for three days would need to supply 90 kilowatt-hours of energy. The battery from the previous example can supply 2.4 kilowatt-hours, so this system would need 38 batteries.

What is the best off-grid power source? ›

Solar power is the most popular and available option when it comes to off-grid energy. How does off-grid solar storage work? Solar panels first convert solar energy or sunlight into DC power using what is known as the photovoltaic (PV) effect.

How many solar panels do I need to charge a 100ah battery? ›

Charging your battery at 12 volts and 20 amps will take five hours to charge a 100 amp hour battery. By multiplying 20 amps by 12 volts, 240 watts is how big of a panel you would need, so we'd recommend using a 300w solar panel or 3 100 watt solar panels.

How much kW is required for a house per day? ›

A smaller house in a temperate region would consume around 210-kilowatt hours (kWh) per month. Whereas a larger house where air conditioners require the most energy might use 2,000 kWh or more. The typical home uses 900 kWh per month. That works out at 1.25 kWh every hour or 30 kWh per day.

What size solar system do I need for 1000 kWh per month? ›

If you live in California, chances are you are going to need sixteen 400W solar panels in order to offset your 1000kWh electricity consumption each month.

How many batteries do I need for a 3000 watt solar system? ›

How many batteries do I need for a 3kw solar system? 1. Lead-acid battery for 3kw solar system, in the statement of 24V, 3000W/24V=125A, if it needs to stay in the best condition, and run at full load for a long time, we suggest you to use 125A*10H=1250AH, 13 batteries in parallel.

How many batteries do I need for a 4000 watt solar system? ›

Batteries are rated as (Ah) which is amp hour, which tell us how much charge or power it can hold so a battery of 12 volts and 70Ah can hold 12volts x 70Ah = 840 watts so to store 4kw you will need approx 5 such batteries but you will still need a charge controller or Inverter to be able to connect and charge these ...

How many 12V batteries do I need for a 3000 watt inverter? ›

If the battery banks you want to purchase are also 50Ah, you will need six of them for a 3000-watt inverter. If your batteries are rated 100Ah, you would only need three, and with 170Ah rated batteries, only two would be required. Remember, the data above is for 12V applications only.

Is it better to have more solar panels or more batteries? ›

The energy produced over the lifetime of typical rooftop solar panels more than makes up for the energy it takes to make, mount and then eventually recycle them. But adding a home battery usually lowers those dividends, according to new research from Stanford University.

How many batteries do I need for a 5000 watt inverter? ›

A 5000-watt inverter would require a minimum 450 to 500 ah 12 V battery. Alternatively, you can have two separate batteries of 210ah 12V that would power the system for 30 to 45 minutes. If you demand to run the inverter for 1 hour, you would require 750ah 12 V batteries.

Which is better on grid or off grid solar? ›

Being grid-tied is beneficial because you don't have to buy an expensive battery back-up system to store any excess energy. Being off-grid means you are not connected in any way to your grid's power system or utility company. This is appealing because you are 100% self-sustaining your energy use.

What is the longest lasting deep cycle battery? ›

OPTIMA 8016-103 D34M is our picks for the longest lasting deep cycle battery with a reliable power solution.

What is the best battery for solar power? ›

Lead-acid and lithium-ion are the two most popular types of solar batteries. Lithium-ion batteries are the best option due to their longer lifespan and larger solar energy storage capacity. However, lead-acid and saltwater batteries are more affordable.

Can a marine battery be used for solar panels? ›

If a marine battery is a deep cycle battery, this will work for your solar installation. However, don't let the 'marine' label overpower everything else, especially if you are looking for solar for a boat or marine application. Any of Renogy's deep cycle batteries will all work great on a boat.

Does solar power work in winter? ›

Solar panels work through all four seasons of the year, come rain or shine, or even hail or in light snow. But solar panels do generally produce less energy in winter. That's because the days are shorter, so there are fewer hours of daylight and the sun is lower in the sky, on average.

Can a home be 100% solar? ›

If your goal is a 100% solar-powered home, you can achieve it with either a solar system that's off-grid or grid-tied. The difference between these is what happens to your excess electricity and how you access electricity when your system isn't generating power.

Can you have too many solar panels? ›

No, there is no limit to the number of solar panels you can have. However, there may be a limit on how much power your system is allowed to generate. Some utility companies limit the amount of electricity that a grid-tied solar system can generate.

What are the design steps to be considered for a PV system? ›

A solar PV system design can be done in four steps: • Load estimation • Estimation of number of PV panels • Estimation of battery bank • Cost estimation of the system.

What is solar designing? ›

In passive solar building design, windows, walls, and floors are made to collect, store, reflect, and distribute solar energy, in the form of heat in the winter and reject solar heat in the summer.

How many solar panels do you need to power a house? ›

An average home needs between 20 and 24 solar panels to fully offset utility bills with solar. The number of solar panels you need depends on a few key factors, including geographic location and individual panel specifications.

Can I build my own solar panels? ›

Making your own solar panel is a time-consuming process and requires some electrical skills. However, it can also be very rewarding – learning to build your own PV panel is a great way to understand how solar electricity is generated.

Can I install my own off-grid solar system? ›

DIY Off Grid Solar Kits have become a lot more popular and If you're looking to install solar panels for a smaller building, such as a holiday shack or shed, it is possible to set up your own stand alone system.

What are the factors to be considered while designing a solar panel? ›

6 factors to consider when installing solar systems
  • Location of the house and inclination of the roof. ...
  • The energy requirement of the property/home. ...
  • The contracting company. ...
  • The durability of the solar systems. ...
  • The expected length of the project. ...
  • The cost of installation.

How much does a battery based solar system cost? ›

A 1 kWh solar system with Battery will cost you around INR 105,000 if you buy it from Loom Solar. It can easily power a 3-4 BHK home and run smoothly for 8-10 hours. A 3 kW off-grid solar system will cost you INR 2,85,000 if you buy from Loom Solar.

What are the 3 main things to consider when designing for passive solar? ›

To be successful, a passive solar home design must include some basic elements that work together:
  • Properly oriented windows. ...
  • Thermal mass. ...
  • Distribution mechanisms. ...
  • Control strategies.

What are the 5 elements of passive solar design? ›

The 5 main elements of passive solar build design
  • The light collector – 'Aperture' The light collector refers to large, sun-facing glassed (windowed) areas in your home at which sunlight can enter the building. ...
  • The Heat Absorber. ...
  • The Thermal mass. ...
  • The Distribution. ...
  • Control.
May 4, 2020

What is solar tempering? ›

Sun-tempered homes

Sun-tempering means making small changes to a home to maximize incidental solar gain. This means orienting the long wall to true south (so the home is on an east-west axis) and moderately increasing the window surface area along the south side.

Can solar power run an air conditioner? ›

You Can Run an Air Conditioner on Stored Solar Power, if:

Proper design and sizing is essential to any solar PV system, but in the case of using solar energy to power your air conditioner, you will need to have enough energy available to cover the hottest days of the year.

What happens when power goes out and you have solar panels? ›

If you have solar panels installed on your roof or property they will continue to generate electricity during power outages, as they do every day because the panels still absorb sunlight and solar energy.

How much does a 4000 watt solar system cost? ›

As of January 2022, the average cost of solar in the U.S. is $2.77 per watt ($11,080 for a 4 kilowatt solar system). That means that the total cost for a 4,000-watt solar system would be $8,200 after the 26% federal solar tax credit discount (not factoring in any additional state rebates or incentives).

What are the 3 types of solar panels? ›

In this blog we will explore the main three types of solar panel cells: polycrystalline, monocrystalline and thin-film. Understanding the difference between the three, is the very first step to selecting your perfect panel for your home, business or community.

Is it cheaper to build your own solar panels? ›

Ultimately, Is It Cheaper To Build or Buy Solar Panels? A DIY solution should cost you less upfront than having a system installed. However, if you build the panels yourself, it may cost you more in the long run. The materials may not be very efficient and may not last as long.

How long do solar panels last? ›

Solar panels, also known as photovoltaic or PV panels, are made to last more than 25 years. In fact, many solar panels installed as early as the 1980s are still working at expected capacity. Not only are solar panels remarkably reliable, solar panel longevity has increased dramatically over the last 20 years.


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