This definitive guide exposes the secrets to various types of solar electric systems for on-grid or off-grid usage.
It reveals to you the building blocks of those solar power systems along with their pros and cons.
By reading this guide, you can discover different ideas how to solar power or back up your home, RV, boat both partially ( i.e. more cost-effectively) or completely.
It will show you how to implement solar power gradually if you are on string budget as well.
In addition, you will discover:
– how you can benefit from a grid-connected solar panels system for your home,
– how an off-grid solar power system will help you meet your daily energy needs,
– what kind of off-grid solar panel system to choose if you live in a remote area and you don’t have access to any utility grid,
– what building blocks your home or mobile solar power system should comprise,
We offer you concise yet comprehensive solar stuff, just read below!
There are two basic types of solar panel systems:
- Grid-direct (on-grid, grid-connected, grid-tied) systems
- Off-grid systems.
The main difference between these two types of PV systems is whether they are connected to the grid or not.
‘The grid’ is the distribution system used by public utility companies to deliver electricity to business and residential consumers.
It includes the network of electrical towers, poles, and wires that are built across the country.
Such a network delivers electricity from coal burning, nuclear or water-generated power plants into commercial buildings and residential houses.
Grid-tied solar panel systems
Grid-tied (on-grid, grid-direct, grid-connected) photovoltaic systems:
- Produce electricity
- Use electricity from the grid
- Export electricity to the grid.
Grid-tied photovoltaic systems:
- Are a source of significant saving from electricity bills.
- Satisfy user’s own energy needs.
- Add value to the building.
- Protect the environment.
- Provide energy backup (for grid-tied systems with power backup).
Grid-tied systems can be designed with or without battery backup.
Grid-tied systems without battery backup are built in regions where power outages rarely happen and for short periods.
Here are the main components of a grid-tied system without battery backup:
A simplified view of a grid-tied solar system without power backup
- Photovoltaic array – generates DC electricity from sunlight
- DC disconnect – disconnects the solar array from the rest of the system
- Inverter – converts DC electricity into AC electricity
- Main distribution panel – the connection point between home electrical network and utility grid
- AC loads – the devices operating on AC electricity
- Net meter – measures the electricity imported from and exported to the utility grid.
In case of power outage, every grid-tied PV system shuts down until the utility is up again.
By shutting the PV system down, technicians that might be doing certain repair works on the utility grid at a moment are prevented from getting an electric shock.
Grid-tied systems with battery backup are preferred in areas where power outages happen more often and by users for whom electricity outage is not an option even for short periods.
If you have a grid-tied system, you use the electricity generated from the system during the day while the sun is shining.
After the sun goes down, your home network automatically switches to using electricity from the grid.
Therefore, you have to pay the utility for the electricity provided during night periods only.
Certainly, you use electricity from the grid when electricity generated by your PV system does not fully meet your household electrical consumption.
Moreover, if your photovoltaic generator produces more electricity than you consume, the ‘excess’ of electrical energy is exported to the grid, for which you get paid.
Grid-tied systems are less expensive and require less maintenance support than off-grid systems.
An obvious disadvantage is that conventional grid-tied systems (i.e. the ones without battery backup) shut down in case of power outage.
This can be avoided by buying a grid-tied system provided with a battery backup option.
Grid-tied photovoltaic systems with battery backup are similar to conventional grid-tied systems except in their ability to provide power backup for critical loads in the event of grid power outage.
The solar array generates power while the sun is shining, thus reducing electrical consumption from the grid.
Should the solar-generated power be not enough for the user’s needs, the excess electricity is provided by the utility.
If however, the photovoltaic system generates more power than needed, the excess solar electricity is exported to the grid.
A grid-tied system with battery backup comprises the following components:
A simplified view of a grid-tied solar system with power backup
- Photovoltaic array – generates DC electricity from sunlight
- Charge controller – regulates battery charging, thus increasing battery lifespan
- Battery bank – stores the electricity generated by the PV array
- Inverter – converts DC electricity into AC electricity
- Main distribution panel – the connection point between home electrical network and utility grid
- Backup loads – all the AC and DC devices provided with power backup
- Non-backup loads – those electrical devices which are not provided with power backup
- Net meter – measures the electricity imported from and exported to the utility grid.
The PV array charges the battery bank via a charge controller.
The charge controller regulates battery charging when the grid fails.
The DC electricity stored in the battery bank is converted to AC electricity by a battery-based interactive inverter and then is delivered to the loads.
Such an inverter:
- Converts DC energy stored in the battery to AC power
- Manages the battery charge via through an integrated charger
- Exports the surplus of energy to the grid thus preventing battery bank from overcharging when the grid is available.
The inverter in a grid-tied system with battery backup is required by the standard to have an ‘anti-islanding protection’.
Such a protection ensures that the inverter is disconnected from the grid during the grid outages, while only backup loads are powered by the solar system.
During grid outage, backup loads are provided with power supply only until there is enough electricity stored in the battery bank.
The obvious advantage of grid-tied systems with battery backup is the ability to provide a backup power supply for critical loads.
The drawback, however, is increased costs both for implementation and maintenance, as a result of adding a battery bank and charge controller.
The cost of the battery bank is usually 20% of the overall system price, batteries are to be replaced every 5 years and, in case of ‘wet’ batteries, their electrolyte needs to be regularly checked.
Grid-tied photovoltaic systems in a summary
| Grid-tied without battery backup | Grid-tied with battery backup | |
|---|---|---|
| Similarities | Connected to the utility grid (the local electrical company) | Connected to the utility grid (the local electrical company) |
| Advantages | -Less expensive -Do not require maintenance | - Your building is not in an outage if the utility fails |
| Disadvantages | - Stop operating in case of a power outage (if the utility fails) | - More expensive (more components to buy/install) - Require more maintenance (as a rule, batteries of residential solar power systems need maintenance) |
When do you need a grid-tied system?
A grid-tied photovoltaic system without power backup is a right solution for you if you are connected to the grid and also if:
- You want to reduce your monthly electricity bill.
- You wish to add value to your home.
- You want to avoid an electricity price increase in the future.
- You search to increase your power security.
- You are passionate about renewable energy from photovoltaics.
A grid-tied photovoltaic system with power backup is the right solution for you if:
- You are a business owner who wants to ensure 24/7 backup and availability of the most important business processes.
- You want to reduce your monthly electricity bill.
- You wish to add value to your home.
- You want to avoid an electricity price increase in the future.
- You search to increase your power security.
- You are passionate about renewable energy from photovoltaics.
Off-grid solar electric systems
Off-grid systems are not connected to the utility grid.
Generally they are preferred in areas where getting connected to the utility grid is too expensive.
In the recent years they are gaining popularity for mobile solar power applications.
Residential off-grid systems are more expensive than grid-tied systems.
There are two types of off-grid systems – stand-alone and hybrid.
Stand-alone PV systems are purely photovoltaic.
Stand-alone systems only rely on solar energy to generate power.
They are not backed by an additional source of electricity.
Hybrid solar power systems are modified stand-alone systems provided with an alternative generator operating by the wind, combustive fuel, etc.
Distinctive features of stand-alone solar panel systems:
- Having implemented power efficiency is of utmost importance.
- Stand-alone systems cannot provide you with unlimited access to electricity.
- Stand-alone systems can take advantage of DC loads (lighting, refrigeration, electronics).
Stand-alone solar photovoltaic systems are typically supplied with battery storage since electricity might be needed when solar energy is not enough (or lacking at all) to generate power, which usually happens:
- In the evening and at night, or
- During year periods of scarce sunlight (in winter or cloudy/rainy days).
When daily electricity needs are too high, a photovoltaic (pv) system relying only on solar energy is not suitable.
Otherwise, a too large and expensive battery bank is needed (which is related to both high initial and maintenance costs), making the purely photovoltaic option far from cost-effective.
In such a case a hybrid off-grid system is the preferred solution.
Hybrid pv systems have additional sources of electricity, apart from the solar array, which supplements the pertaining battery storage.
A stand-alone photovoltaic system is a right solution for you if you cannot get connected to the grid and also if:
- You need electricity 24 hours a day.
- You are passionate about renewable energy from photovoltaics.
- You are not fond of combustible fuel generators based on diesel, propane, petrol or natural gas.
- You do care about environmental pollution and want to preserve the Earth’s fuel resources that are running out.
In a typical stand-alone solar system, the electricity produced by the PV modules is used for charging batteries through a charge controller.
The charge controller, however, as well as the battery bank, might not be needed.
Inverter might not be needed either.
There are stand-alone PV systems (directly-coupled ones, see the table above) where a DC load is connected directly to the solar array – like in pump stations, for example:
Such stand-alone PV systems are called ‘directly coupled’.
They are the simplest and the most used ones, since they:
- Only comprise a PV array, a battery (optional) and loads, and
- Are used in wide range of applications.
| Directly coupled standalone solar power systems | Applications |
|---|---|
| Standard DC motors, DC fountain pumps, DC cooling fans (all of them known as ‘day-use appliances’); various mobile solar panel applications – caravans, campers, RV, motorhomes, etc. |
 | Small devices, pocket calculators, watches; various mobile solar panel applications – caravans, campers, RV, motorhomes, etc. |
If the solar array is intended to power AC loads, an inverter is needed.
Inverters in stand-alone PV systems are different from inverters in grid-tied systems, although they apparently do the same – convert DC into AC electricity. A stand-alone inverter and a grid-connected inverter cannot be used interchangeably.
In stand-alone solar power systems, it is very important that the electricity produced by the PV array should be enough to meet the energy needs of the all the electrical loads the PV system is connected to.
Here are some more configurations of stand-alone systems:
 | Electricity is only needed while the sun is shining – cooling fans, pumping & irrigation equipment. |
 | The system is provided with battery storage, usually combined with a charge controller, so that the electricity produced can be used later. |
The requirements for the solar arrays in grid-tied systems are also applicable for stand-alone systems.
Anyway, you should mind the following:
- Stand-alone systems are usually built in rural areas, away from cities, including the solar systems installed on vehicles. This means that there are more options for installing solar panels. Typically the panels of the solar power systems for homes are located on the ground rather than on the roof. As to mobile solar electric systems, both options are popular, regardless of the specific solar panel type used.
- Solar electric systems for homes are supposed to operate well all the year round. Since in winter sun is located lower in the sky and nearer the horizon than in summer, in winter PV arrays orientation requires a higher slope. Such a higher slope is much easier to achieve with a solar array mounted on the ground rather than on a roof.
- In a stand-alone system, whether for home or mobile, the target is to provide all the facilities to store the energy produced in order to be able to meet the consumption needs at any moment. Often such a moment, however, does not coincide with the solar array’s period of maximum power yield.
When using electricity generated by a battery bank, you should use compact fluorescent light bulbs, eliminate phantom loads and unplug any resistive loads – devices using electricity to generate heat, i.e. water heaters, room heaters, electric stoves and cookers, even incandescent lamps.
Fuel generators, however, support resistive loads, so you cannot backup them by batteries.
You are not bound by all means to a single bulky stand-alone photovoltaic system meeting all the needs possible.
Often several small systems are more advantageous than a single system.
This is valid especially if you intend to power a couple of electrical devices, independently from each other, as is the case with campers, motorhomes or RV, since smaller systems are always easier to manage and maintain.
| Off-grid system modification | Applications |
|---|---|
| Standard DC motors, DC fountain pumps, DC cooling fans (all of them known as ‘day-use appliances’); various mobile solar panel applications – caravans, trailers, RV, motorhomes, etc. |
| Small devices, pocket calculators, watches; various mobile solar panel applications – caravans, trailers, RV, motorhomes, etc. |
| AC motors, AC pumps |
| Various mobile solar panel applications – caravans, trailers, RV, motorhomes, etc., telecommunications, medical cooling, bus station lighting, small residential solar systems |
 | Off-grid hybrid systems: in homes, schools, hospitals in remote areas, often in combination with an additional power source – a wind turbine or a diesel generator. Off-grid hybrid systems are explained below. |
Off-grid stand-alone PV systems have the following benefits:
- A reliable source of power.
- Practically unlimited in size – a stand-alone system could serve a single device or a couple of buildings with a complex electrical network.
- Can be installed almost anywhere in the world.
- Can be less expensive than paying for getting connected to the utility grid (if the utility grid connection point is located miles away).
- Can provide electricity to the most household devices.
- When properly adapted, they are suitable for various mobile solar panel applications – caravans, campers, RV, motorhomes, etc.
Limitations of stand-alone photovoltaic power systems:
- Unless your building is located too far from the utility grid, replacing the utility grid with a stand-alone PV system is not cost-effective.
- Due to solar radiation variability, a PV system does not deliver a maximum performance all the year round. In winter, it is often more cost-effective to buy a hybrid system than to spend a fortune on a battery bank and rely solely on solar generated electricity.
- The electricity produced by the PV array can be stored in batteries for a limited period only.
- Making your home energy efficient is a must before buying a residential stand-alone system.
- The battery banks used in most home off-grid systems require a separate, well-ventilated room, as well as specific operation and maintenance activities.
You can learn more about off grid solar panel systems for home, cabins, RV, campers and boat in our bestselling book/paperback or kindle edition/ “Off Grid And Mobile Solar Power For Everyone: Your Smart Solar Guide available on Amazon”
You can discover how this book helps you get fast and easy an off-grid or mobile solar power system for your home, cabin lodge, RV, van, motorhome or camper by watching the video below:
Click Here to Get This Book Now on Amazon
Hybrid off-grid solar electric systems
Whether to choose either a stand-alone (purely solar) or a hybrid off-grid photovoltaic power system depends on:
- Whether you use the building on a yearly or on a seasonal basis.
- Whether the site is easily accessible or not.
- How much total daily you need.
- What kind of electrical applications you use – whether critical or not.
In a hybrid system, the alternative generator is usually a diesel, propane or gasoline one, and less commonly – wind generator.
As a rule, hybrid systems are recommended when daily energy needs exceed 2.5 kW.
Certainly, a hybrid system is recommended always when the available sunlight in your area is not enough to meet the desired days of autonomy, and this would result in a costly battery bank.
A backup power generator modifies a stand-alone photovoltaic solar system into a hybrid one.
A hybrid system is a combination of a photovoltaic generator and an alternative power generator – wind or fuel one.
Such a generator charges the batteries upon lack of sunlight and is used either as a backup one or when the PV system alone cannot meet the specific energy demands.
Block picture of a hybrid solar power system
In a hybrid system, the combustive fuel generator is a source of AC electricity, which, after having been converted to DC electricity, is stored in batteries.
Batteries are charged both by the PV array and the generator.
The available loads in the building draw power from the batteries.
Additional power backup sources in hybrid photovoltaic systems
Actually, you could do without a backup generator in a stand-alone system but at a higher cost – you have to oversize your system and choose a battery bank of a rather high capacity. Such a strategy, however, is highly impractical for two reasons:
- The initial cost of batteries is extremely high.
- Such a system will work with maximum performance just a few months throughout the year (probably in winter), while in the rest of the time it will work far below its maximum efficiency. Therefore, the value of the electricity produced probably will be not enough to cover the expenses needed for the maintenance support of the battery bank.
The wind and fuel generators on one side and photovoltaic generators on the other side have rather few in common.
This implies the need for additional knowledge of different technologies, each one having its own specifics.
The minimum overlapping, however, means that the drawbacks of the first technology can be easily compensated by the advantages of the other one.
A wind generator appears as a relevant supplement to solar generator since in general windy periods very often coincide with periods of sunshine lacking (for example, during cloudy weather or at night).
What is more, the practice has proved that a combination of a solar generator and a wind generator often makes redundant the use of an additional fuel generator.
Fuel generators are the most popular power backup generators.
Their main advantages are:
- Low initial expenses
- Available on demand
- Portable
- Widely spread in various modifications.
Here is a list of their drawbacks:
- Relatively costly maintenance
- Noise pollution
- Air pollution
- Low fuel-to-power conversion efficiency – maximum 25 % but upon partial loading can go even below 10%
- A lot of the energy produced is dissipated as heat
Fuel generators (as well as wind generators) are sources of AC power.
In a stand-alone solar system, the AC power produced by the fuel generator is used:
- By the existing AC loads
- By the battery charger to generate DC power used by the existing DC loads.
PV arrays and fuel generators do not produce the same kind of electricity.
PV generators are sources of DC power.
In a stand-alone solar system, the DC power produced by the PV generator is used:
- By the existing DC loads
- For charging the battery bank.
Upon enough sunlight, the needed AC power at the site is provided by the inverter converting the DC power produced by the solar array, into AC power.
When sunlight is insufficient, the needed AC power at the site is provided by the fuel generator.
When compared to wind generators, fuel generators have some benefits:
- Quite an affordable price
- Easy to launch
- Highly portable
- Operate independently on weather, at any time of the day.
In hybrid systems, fuel generators do not operate continuously but rather during sunless periods only.
This means that they have:
- A more efficient use of fuel
- A longer life-cycle
- Lower maintenance costs
A well-designed photovoltaic system needs running a fuel generator between 50 and 200 hours per year.
Benefits of hybrid solar power systems in a summary:
- A cost-effective solution, except for the remote spots with difficult access (where maintenance and fuel delivery can be quite expensive).
- Low initial cost – fuel generators have affordable prices and there is a great variety of models available at the market, compared to the high initial cost of batteries and PV modules to provide the desired number of days of autonomy if a generator is lacking.
- Increased reliability – there is a simple rule “2 is more than 1”, which is applicable if there are two instead of one battery charging sources – a PV array and a generator.
- Increased efficiency – a fuel generator is used not only to charge the batteries but also to provide power to the loads operating simultaneously at a given moment. Therefore, a generator could be turned on together with a large load consuming lots of power (a dryer and a washing machine). If such loads are not turned on every day, this might be a preferred way to avoid supplying them with power from the PV array and the battery.
When do you need a hybrid solar photovoltaic system?
A solar power system is recommended:
- If the daily consumption of electricity exceeds 2.5 kWh.
- For regions with poor sunlight for long periods of time.
In these two cases, a stand-alone solar system cannot meet your energy needs.
You can learn more about off grid solar panel systems for home, cabins, RV, campers and boat in our bestselling book/paperback or kindle edition/ “Off Grid And Mobile Solar Power For Everyone: Your Smart Solar Guide available on Amazon”
Other types of photovoltaic systems
Grid fallback system
Grid fallback system is a relatively new photovoltaic system type which is very advantageous for low-power residential photovoltaic systems.
Grid fallback is gaining popularity since it is operationally efficient, cost-effective and environmentally beneficial.
In a grid fallback solar system, the PV array generates power, thus charging a battery bank.
Electricity is taken from the battery bank and then run through an inverter to power all the circuits connected to a secondary distribution panel. Since the solar array generates low power, it can power a part of the loads in your house.
The rest of the loads are always powered by the utility grid via the main distribution panel.
Grid fallback solar photovoltaic system diagram
In case of utility grid failure, protected loads will be powered by solar array only upon enough capacity in battery bank available.
Upon battery discharge, the system automatically switches back to the grid power supply.
After the battery bank gets recharged by the photovoltaic array, the solar system switches back to the solar array.
Usually, such a system is economically viable if it generates less than 1 kWh of energy per hour, which corresponds to a solar array of up to 500-750 Wp installed power.
The main feature of a grid fallback system is that electricity is not sold to the utility grid but rather used for user’s own needs.
Therefore, you might not be allowed to take advantage of some of the subsidies provided by the government in some countries.
Furthermore, you cannot benefit from selling electricity to your local power provider.
For this reason, implementing a grid fallback system appears more reasonable in countries with no feed-in tariff available (like India) or in countries where financial incentives are provided both for grid-tied and off-grid systems (like Australia).
Actually, grid fallback systems offer you most of the advantages of a grid-tied system with battery backup, with the added benefit that you can use the power your own system generates at any moment you need, not only while the sun is shining.
This eliminates your dependence on external power providers which is perfect especially during peak load periods.
As mentioned above, a grid fallback system is cost-effective.
It allows you to power one or more additional loads in your home for a very small investment and to expand the number of those loads according to your budget, as shown in the picture above.
A grid fallback system installed for about $700 provides a fair amount of power for a home, while even a small grid-tied system would cost a couple of thousand dollars.
When is a grid fallback system more advantageous than a typical grid-tied system?
1 kWh is considered the boundary between a grid fallback and a typical grid-tied system.
If the solar array is capable of generating more than 1 kWh of energy, a grid-tied system would be the cost-effective solution. If the PV array, however, generates less than 1 kWh of energy, a grid fallback system would be a less expensive solution.
So, unless your goal is to produce much more than 1 kWh of energy thus taking advantage of feed-in tariffs (and certainly investing a substantial amount of money in a larger grid-tied system), a grid fallback system is much more attractive as a solution for your home energy needs.
When is a grid fallback system more advantageous than a typical grid-tied system?
1 kWh is considered the boundary between a grid fallback and a typical grid-tied system.
If the solar array is capable of generating more than 1 kWh of energy, a grid-tied system would be the cost-effective solution.
If the PV array, however, generates less than 1 kWh of energy, a grid fallback system would be a less expensive solution.
So, unless your goal is to produce much more than 1 kWh of energy thus taking advantage of feed-in tariffs (and certainly investing a substantial amount of money in a larger grid-tied system), a grid fallback system is much more attractive as a solution for your home energy needs.
Grid failover system
A grid fallback system could be configured as a grid failover system. Such a system is run by a power outage by your utility company.
In this case, automatic switching box switches the solar-generated electricity to the secondary distribution panel and the protected loads connected to it.
Grid failover solar photovoltaic system diagram
The unprotected loads connected to the main distribution panel are not powered.
Protected and unprotected loads are normally powered by grid energy via the Main and Secondary distribution panels, while the solar array charges the battery bank in the daytime.
Thus grid failover system acts like a UPS (Uninterruptable Power Supply) powered by solar electricity.
This is quite beneficial if you wish to be grid-independent and you need to provide continuous power to some critical parts of your production cycle, or to the most important loads in your household.
The drawback of such a configuration is that the solar electricity generated by the system is not used for your daily needs.
Grid failover system is, therefore, recommendable in countries with occasional grid power outages, for example in Africa and some parts of Asia, rather than in Europe and America.
Sources:
1. Boxwell, Michael. 2012. Solar Electricity Handbook, Greenstream Publishing, Amazon Kindle Edition.
2. Antony, Falk, Christian Durschner, Karl-Heinz Remmers. 2007. Photovoltaics for Professionals: Solar Electric Systems Marketing, Design and Installation, Routledge.
3. Mayfield, Ryan. 2010. Photovoltaic Design and Installation for Dummies, Wiley Publishing Inc.
You also may like:
Can Solar Panels Power a House?
Connecting Solar panels: Mixing Solar Panels
How Many Solar Panels Do I Need to Power My House or RV, camper and Boat
Free Solar Panel Calculator and Solar Power Calculator
Latest posts by Lacho Pop, Master of Science in Engineering (see all)
- The Ultimate Off-Grid and Mobile Solar Power Bundle: 2 Books in 1 - August 10, 2021
- The Ultimate Guide to Solar Lights and Solar Photovoltaic Lighting Systems - February 1, 2021
- Solar Battery Monitors Demystified: Battery Monitor For RV And Off-Grid Solar Power Systems - October 18, 2020
