Please can you check the FAQS below as these may help with your issue.




On Grid

Off Grid

Solar Panel Systems







Where should I install panels?

The solar array of a solar panel system is mostly mounted on a buildings roof, generally with a gap around 10 cm parallel to the surface of the existing roof. If the rooftop is flat, then the array is mounted with each panel aligned at an angle to maximise the solar irradiation.

If the panels are planned to be mounted before the construction of the roof, the roof can be designed accordingly by installing support brackets for the panels before the materials for the roof are installed. If the roof is already constructed, it is relatively easy to retrofit panels directly on top of most existing roofing structures.

For a small minority of roofs the existing structure or outer material is not ideal or not designed so that it is capable of bearing the additional weight of installing solar panels. This would mean selecting another location or could demand that the roof structure must be strengthened beforehand.

What is a Tier 1 solar panel?

Callidus prefer to use a Tier 1 panel. Tier one panels are classified based on the volume of large scale projects using them within a specific time frame and carry Tier 1 status as they are a preferred product. Our current Q-Cells or JA solar panels are both Tier 1 approved.

What are the laws with installing solar panels?

There are strict laws and compliance in place to protect consumers, installers and contractors in solar PV. This is not something you can try at home. There is a serious risk of death and systems are designed to protect you at all times, but this is live electricity and just like educating a child not to put fingers in sockets, the same rules apply. Don’t touch things that could cause harm. Call the experts or professionals.

What is the best area for solar panels?

An area to install the panels that is free from shading or obstacles that can block out the sun. It needs to be around 20m² for a 4KW system.

What size area do I need for solar panels?

A solar panel is between 1.7m² & 2.1m². The smaller panel usually is less in watts and therefore you need more of them to get to the same size output of a larger panel. A standard 4kW system would take up around 20m². With all solar panel installations we need to leave a border or gap from the sides of the roof. This is worked out by our surveyors when they attend your location.

Can I install panels on many different roofs?

There are few ways to overcome some of the problems installers face when working with multiple panels. One is to use a string inverter with multiple inputs each with MPPT capability. This allows for different strings, not modules to have different orientation, tilts and module types without having one string hinder the performance of the other.

The second option is to add DC optimisers to the string inverter system; these are like the micro-inverters. DC optimizers are installed at each module and make adjustments to the output on an individual basis.

How do solar panels actually work?

The science of turning sunlight directly into electricity is known as photovoltaics, or PV referring to photons of light and volts of electricity. Solar panels now more commonly known as PV modules contain solar cells which are mostly made of layers of silicon and a semiconductor material made from sand. (This silicon product is the most expensive part of the panel).

When photons of light enter the solar cells they get absorbed and the electrons get excited and start to move within the silicon layers causing them to ultimately flow continuously through a circuit of wiring that feeds into the PV system. Harnessing these quickly flowing electrons is what gives you a electrical power. Electricity produced by Solar PV modules or panels and the power used by all batteries is direct current, abbreviate to DC. This is where all of the electrons move in one direction only. DC is the more dangerous of the currents.

Your homes electrical system and most appliances use AC known as alternative current. With AC power the electrons move back and forth in an alternative direction and at around 60 times per second. Due to the two different currents, PV systems include one or more inverters that convert the DC solar generated electricity to a usable AC power for your home. Once the power is converted to AC any over production can be sold back to the grid. 

All home PV systems start with a collection of Solar Electric modules (PV or Panels) called the PV array the array can be installed on a roof or on the ground. The modules in an array are usually wired together in groups each called a series or string. These strings are joined near the array at a junction box or other device, and wiring from the box taking the power to the rest of the system components usually at the ground level. The first component that the supply lines connect to depends on the type of PV system. (On Grid – connected to the main grid, or Off grid – no main incoming supply)

Should I have a string inverter or micro-inverters?

It’s true that micro-inverters have some great features and may seem like the first choice in designing a new solar system but there are some good reasons why Callidus and other industry experts would always opt for a string inverter, they are dependable & reliable option for the Solar industry when designing systems.

What does the glass do on a solar panel?

The outer glass pane is the first line of defence. This glass panel protects the solar cells from dust, dirt, debris and any other pollutants. The glass is also made up of an anti-reflective material. This anti-reflective material helps prevent the rays of the sun from being reflected, hence there is a maximum absorption of the sun’s rays by the solar panels.

What does the back sheet do on a solar panel?

The back sheet also helps in keeping the frame, solar cells, encapsulates and glass together. The back sheet also secures the panel junction box. 

What are solar PV or photovoltaic panels?

Just like the great British sandwich, solar panels are made up of many layers each of which has a unique role to play. Panels are made up of the outer frame, the solar cells, glass, encapsulates, a back sheet and a junction box. All of these layers make up the complex solar panel.

Can I add to my existing solar system?

Callidus are able to extend your existing solar system or add batteries to an existing system to maximise the benefits of generating your own power and not sending it back to the grid. If you already have a solar system that is 3kW or 4kW, then it will likely already be around 16amps. If we need to add another inverter, then this will require a G99 Application. Callidus will do this for you and it will then be a lawful addition to your existing solar array.

What is the difference between monocrystalline and polycrystalline solar panels?

The main difference between the two technologies is in the crystal purity of the panel cells. Monocrystalline solar panels have solar cells made from a single crystal of silicon while polycrystalline solar panels have solar cells made from several fragments of silicon melted together. The crystalline purity of the cells of monocrystalline solar panels is therefore much higher than that of polycrystalline solar panels. The image below shows you how to distinguish the two different types of solar panels. Monocrystalline cells are black and octagonal while polycrystalline cells are dark blue and squared.

What is the difference in performance?
The efficiency of a solar panel is the ratio between the amount of energy it collects compared to the amount of energy it produces, the rest being lost in heat. An efficiency of 20% means that 20% of the solar radiation is transformed into electricity and that the missing 80% is transformed into heat.
The higher the efficiency, the greater the amount of electricity produced.
That said, monocrystalline solar panels perform better than polycrystalline solar panels due to the fact that monocrystalline solar cells are composed of a single crystal rather than a conglomerate of crystals, which increases their spectral response and thereby their energy production. Concretely, the efficiency of monocrystalline solar panels varies between 16 and 24% while that of
polycrystalline solar panels varies between 14 and 20%. That means that on an equal surface, monocrystalline solar panels are more efficient. These panels are often suggested for those whose space is a limiting factor. In summary, monocrystalline solar panels have solar cells made from a single silicon crystal while polycrystalline solar panels have solar cells made from multiple fragments of silicon crystals melted together. This manufacturing difference means that the spectral response of monocrystalline solar panels is higher, which gives them better performance. Although they are more expensive, the fact
that they can produce more energy offsets their additional cost, especially knowing that their lifespan is at least 25 years. In addition, their black colour is more discreet


Can I control the available amount of power left in the batteries in the event of a power cut?

Yes, this can be programmed by you or us to a level you are happy with. This applies to the Callidus board socket or the complete home islanding if you have selected this upgrade. 

Can I add batteries to my existing solar panel system and old inverter?

Callidus offer a battery system to compliment almost any existing solar installation. This can really help you get the most out of your system and store the power you generate rather than send it back to the grid. We can even add additional panels and batteries to make a more powerful system for additional electrical use. 

AGM or Gel?

AGM (absorbed glass mat) uses special design glass mat designed to wick the battery electrolyte between the battery plates. AGM batteries contain only enough liquid to keep the mat wet with the electrolyte and if the battery is broken no free liquid is available to leak out.

Gel Cell batteries contain a silica type gel that the battery electrolyte is suspended in, this thick paste like material allows electrons to flow between plates but will not leak from the battery if the case is broken.

More often than not AGM Batteries are mistakenly identified as Gel Cell Batteries. Both batteries have similar traits; such as being non spillable, deep cycle, may be mounted in any position, low self discharge, safe for use in limited ventilation areas, and may be transported via Air or Ground safely without special handling.

AGM Batteries outsell Gel Batteries by at least a 100 to 1. AGM is preferred when a high burst of amps may be required. In most cases recharge can be accomplished by using a good quality standard battery charger or engine alternator. The life expectancy; measured as cycle life or years remains excellent in most AGM batteries if the batteries are not discharged more than 60% between recharge. There are some AGM batteries we sell that offer excellent 80%+ deep cycle abilities.

Gel Batteries are typically a bit more costly and do not offer the same power capacity as do the same physical size AGM battery. The Gel Cell Battery excels in slow discharge rates and slightly higher ambient operating temperatures. Not recommended to work with an inverter. One big issue with Gel Batteries that must be addressing is the GEL CHARGE PROFILE. Gel Cell Batteries must be recharged correctly or the battery will suffer premature failure. The battery charger being used to recharge the battery(s) must be designed or adjustable for Gel Cell Batteries. If you are using an alternator to recharge a true Gel Cell a special regulator must be installed.

What are AGM batteries?

Callidus would recommend an AGM or (Absorbed Glass Mat) battery. Lead acid batteries are best for occasional use and not continual discharge. For continual charge and discharge Callidus would recommend you opt for a lithium battery. AGM batteries are also more versatile in different temperatures, this is really important as the AGM batteries work within a temperature range of 32 and 104 degrees Fahrenheit (0 and 40 degrees Celsius).

What are Lithium batteries?

Lithium batteries are far better at charging and discharging and prefer to be kept in this state although they have a limited working temperature. They are sensitive to heat and work best between 15 and 25 degrees. The major benefit as they can do 6000 Cycles. When using the batteries correctly this can give them a life span of 16.4 years

What are batteries used for in Solar installations?

We are all used to swapping over the batteries around Christmas trying to find a pair to work for the kids toys, or rubbing them together to get that last bit of charge to work the remote, but the reality is batteries are very complicated for PV systems and we could easily fill several pages for there are many types, sizes, prices, characteristics, behaviours also countless personal experiences and opinions from across the world of Solar.

Batteries often perform differently for different PV systems and under varying solar irradiation, temperature and electrical load conditions. The reality is batteries last between 5 and 8 years although most of our newer types are predicted to last between 10 and 15 years so you could go through one or two sets of batteries in the life of your PV system. (PV systems over 40 years old are still generating good amounts of electricity).

What batteries should I have or use on my system?

For regular use Callidus advice would be to only use deep cycle batteries which are designed for the regular deep discharges of a PV system. This compares to standard batteries, like a car battery that is designed for a quick burst of discharge to start the engine followed by immediate recharging while the engine is running.

The deep discharge of a PV charge/recharge cycle would quickly destroy a car battery. Callidus use sealed lead acid batteries. They cost a little more but they have a greater storage capacity and are very little maintenance and often referred to as maintenance free.

What do I need to do for battery maintenance?

All batteries should be monitored regularly to make sure they are charging and discharging properly but in terms of manual maintenance this usually means flooded lead acid and this is not something Callidus would offer although it can be done safely by a professional. Most of our batteries are simply a plug and play system and don’t require any maintenance.

What is battery capacity?

Battery capacity is measured in Amp-hours. AGM and other standard deep cycle batteries for PV systems might have an individual capacity ranging anywhere from 100 to 500 amp hours each. There is a simple calculation to work out battery capacity.  We simply multiply the voltage of the battery by the Amp-hours rating. A 12-volt 200 amp hour power battery can discharge 2400 watt hours or 2.4 kW hours of energy. There may be some small efficiency losses from converting the power from DC to AC and minor losses through cable runs.

What is the battery cycle life and depth of discharge?

Cycle life is always an estimate of how many times a battery can complete a single cycle of discharging and recharging. Under normal conditions batteries in an off-grid system this would be one cycle per day. Cycle life ratings for deep cycle batteries typically range from 500 to 3000 Cycles. The life span of Deep cycle batteries last longer if they are discharged no more than between 50% and 80% with each cycle.

Lead acid batteries should not be discharged to below 50%, where lithium batteries can be discharged up to 80%. No battery should be discharged more than 80% it significantly shortens the life of the battery. Please always note the manufacturer’s recommended depth of discharge (DOD) when comparing cycle life and battery capacity.

How should I monitor the battery performance?

Batteries for solar systems are incredibly heavy and we would advise against trying to move or lift them once they have been installed. An average battery can weigh in excess of 100 kg. They are not like the battery in your remote control and can have cable and switches attached for on-line monitoring and performance. The Pylon lithium batteries are stored in a purpose build cabinet and come in banks of 4.

Is it possible to have the battery system charged from the grid supply?

Yes, many companies like Octopus Energy have a tariff that is more reasonable at night allowing you to charge your batteries at a cheaper rate than standard daytime electricity charges.

Is the battery storage expandable in the future (i.e. could additional capacity be subsequently added)?

Yes, Callidus battery systems are expandable and it is a fairly simple process.

Can I have Solar Micro inverters, or Optimisers with a battery system?

Callidus Battery storage systems use Victron parts and we use an MPPT (Maximum Power Point Tracker) this works the same way. You can have batteries with SolarEdge products.  

SolarEdge have their own battery system called Energy Bank. This is a 10kW battery that connects at the DC side and offers customers with optimisers a solution to battery storage.


On Grid

What is On Grid Residential?

An on grid system is the most common type of residential PV system as well as the simplest to install and the least expensive. It connects to the grid and uses the grid for both supply and backup. When the array creates more power than the house uses the excess power is fed back into the grid – this can create an SEG (Smart Export Guarantee) payment, previously known as the ‘export tariff’. When the house needs more power than the solar array provides the house automatically will pull electrical power from the grid.

What is On Grid Commercial?

Most commercial buildings are connected to the grid and usually have a 3 phase incoming supply. Callidus are considered experts in commercial solar installations and will help your business be less dependent on the grid, but still power your business without interruption.

What are the advantages of being on grid?

The advantages of an on grid system include its simplicity, it’s low cost and low maintenance making it the obvious choice for most homeowners and businesses who are buying electricity from one of the big six suppliers. This is the majority of the UK. But the grid can also be the main disadvantage of an on grid system and this is all about safety.

When the grid goes down and we experience a power outage, so does the PV system. This automatic shutdown function is called self-islanding and is required by all installations for on grid systems for the safety of engineers potentially working further down any power lines. If your system started to export back to the grid while people were working on fixing the problem the result is life threatening.

How big can my system be if I am connecting to the grid?

This all depends on whether you are residential or commercial premises. If you’re a residential single phase home with a grid connection then you are limited to a 3.68kW inverter without doing a G99 Application. We can go above this, it just means we need to do the G99 application. This means we can put a much larger system into your home and then limit the export to 3.68kW.

This is signed off with the G99 form. If you are a 3 phase or commercial property then the options are different and we would need to look into this for you in more detail. Currently it’s free to complete many of the applications with the District Network Operator (DNO) or your local supplier E.G. SSE


Off Grid


What is Off Grid?

The ultimate self-sufficiency power system. Off grid systems have no connection to the national grid and therefore the best choice for new homes or properties far away from the national grid. (Grid connection costs have climbed in recent years and we have seen quotes from £18,000 to £100,000 for new connections to a remote location).

Off grid systems always include a bank of batteries for storing solar generated power during the day and feeding this power back to the property at night. These systems may also get additional backup power from a fuel powered generator. Solar electricity goes through the inverter charger to the batteries or to the property.

The property is not directly powered from the array. Batteries are charged by power from the array going through the inverter charger. The inverter charger also monitors and controls how the power is converted for a better before supply to the property.

What is a Callidus Off Grid Hybrid?

Callidus offer a hybrid version of an on grid system that can combine with battery backup. Solar power can feed the property, charge the batteries and feed back to the grid. When there’s an excess and the house needs more power than the solar array produces it can pull from the grid or the batteries.

If the batteries are getting low and the PV array is not providing enough power to charge the batteries, then the system will use the power from the grid to recharge the batteries. When the grid goes down the batteries supply power to the property circuits this enables you to keep important things like a fridge lighting computers running during power outages the batteries typically do not power the entire house as this would require a larger more expensive battery bank.

With the current increase cost of wholesale gas effecting the direct unit cost of electricity, many home owners are adding battery storage to their system rather than exporting electricity and collecting the SEG payment.


Solar Panel Systems

Can I have a system larger than 3.68kW?

Many people believe a system on a residential property is restricted to 4KW. This is not the case and the system can be double this if it suits your usage. There are some rules around what can go back to the grid and this is always restricted to 3.68KW. Anything over this would require a G99 Application that we can complete on your behalf with your written consent.

Can I have full, complete or whole home islanding?

Callidus can offer ‘Complete home islanding’ this is a fair amount of work and our standard charge for this is £1600 ex Vat and Vat is only 5% if this is part of the complete installation. You need to make sure that you just have a base load running and not have lots of high use items in the event of a power cut, otherwise the batteries can be quickly depleted and then you are waiting for the sun to come back up and power your home/charge your batteries, or the grid to come back online. 

With ‘Complete home islanding’ you are able to run most items in your home as you would with a grid connection. The solar inverter charger and batteries are always working, so if it is daylight, then the panels will power your home and if over producing, charge the batteries. When the sun goes down you are on battery only.

If I have the complete home islanding in the event of a cut would the circuits in my home remain ‘live’ with no interruption?

Yes, it’s seamless and you wouldn’t even know as long as you have solar power, or power in the batteries. The output will be dependent on your inverter charger output which is 4.4kWh on a 5kva inverter.

Is there any way that I could be made aware that the mains supply to the house has failed?

Yes, we install a light close to the metering point, above a door or nearby that lights up in the event of a power cut, so you are fully aware (Only when having the complete home islanding installed).

What power limitations can I expect on my system?

The power from the system is limited by the size of the inverter. For example a 5kva inverter charger will give 4.4kW/h. 4.4kW is the highest output. This covers most typical home base loads. We can put 2 x 5kva inverters in parallel and this would offer 8.8kW maximum output.

Is weather sealing important?

In all cases of retrofits particular consideration to weather sealing is necessary. There are many low-weight designs for Solar PV systems that can be used on either sloped or flat roofs, most however, rely on a type of extruded aluminium rail (e.g. Renusol).

What are rail and mounting systems?

Photovoltaic mounting systems, also called solar module racking are used to fix down solar panels on surfaces like roofs, a buildings structure, or to the ground. These mounting systems are designed generally to enable retrofitting of solar panels on an existing roof or as part of the structure of the building. They anchor with brackets and are designed to cope with all the elements in mind, primarily wind. Most PV mounting systems are designed to last for the life of the system using strong lightweight materials like aluminium and stainless steel.

Residential systems over 3.68kW and G99 applications

We can install systems that match your usage provided you have enough room for all the panels and battery storage area. This means we have to use larger inverters and inverter chargers. If you have a grid connection, then we are limited to the products we can use and in most cases on a domestic property we can’t use an 8kva, or 10kva inverter charger, it would need to be 2 x 5kva as this is permitted. Any on grid domestic property going over 3.68kW will need a G99 application.



The difference between PWM & MPPT

What is Voltage?

This is the electrical potential of the circuit.

What is Current?

Current is the flow of electrons and can be seen as the kinetic energy of the circuit. Current is the element that actually flows through the circuit.

What is Resistance?

Resistance is the opposition to the flow of current and it can be compared to friction like the tires of a car when driving on the road.

What are Transistors?

Transistors make up the solar cells and are capable of converting the light from the sun into electrical energy.

What is a Kilowatt hour?

1x kilowatt hour or kWh is equal to 1 x unit of electricity. (New average is between £0.28p and £0.36p /kWh).

What is a Module?

A module is simply another name for a solar panel. Several modules make up an array.

What is an Array?

The array is the group or string of panels within a system.

What are Strings in a solar system?

Strings is the name given to the linking of panels. You could have an array made up of 10 panels and this would be on 2 strings of 5 panels (If this was 20 panels it would be 4 strings of 5 panels).

What is the outer frame?

The frame helps in holding all of the layers of the solar panel together; it also helps in preventing damage that might take place during transportation of panels. It is a key component to securing the panels on the mounting system of a roof or ground mount system. (On roof mounted systems are more reasonable than ground mounted systems).

What are Solar Cells?

The solar cells are made up of transistors. These transistors are capable of converting the light energy given by the sun into electrical energy. The transistors are made up of a silicon material and this is where the actual conversion of energy takes place.

What are Encapsulates?

Encapsulates are the second line of defence for the solar panel. They hold the solar cells in place and help in keeping the panel together.

What is a solar panel Junction Box?

This is the output for the entire solar panel. It usually consists of two wires; one end of the wire is connected to the solar cells internally, the other end of the wire as the output.

What is a unit cost?

This is how much you currently pay, or will be paying for 1kWh of electricity. This can range from £0.28p to £0.36p /kWh. We will need to know this information so we can work out how much a system may save you on your bills.

What are Inverters and optimisation?

There are two main types of inverter for residential or on grid systems: String inverters and micro inverters there is also another option called DC optimizers designed for a string inverter system like SolarEdge.

What are String Inverters?

String inverters are quite large units that usually mount on a  wall or a cupboard at ground level. They are often near the rest of the components (MPPT, Switches and Isolators) and usually in a garage or storage area. They are designed to be enclosed and not on external wall. (Although some are weather rated for external mounting like the Tesla Powerwall.)

They receive DC power from the series strings from the array and deliver AC power to the electrical circuit  of the property. Most residential PV systems with string inverters have one or two inverters depending on the array size and the layout. String inverters for an on grid system are commonly referred to as a ‘grid tie’ inverters to distinguish them from standalone and  sometimes known as ‘battery inverters’.

String inverters get input from modules as strings (a group of panels) not as individual modules. The inverter monitors and optimises the output of the entire string. This is because the inverter can’t distinguish or separate one panel or module from the other.

What are Micro-inverters?

Micro-inverters are small units that mount onto the back side of each module or onto the panel / array railing system below the modules. Typically each module has its own micro-inverter although some micro-inverters can feed from two modules. Micro-inverters convert DC power to AC power from the individual module so the wiring that connects the modules and runs back to the property consumer unit already carries AC electricity.

Micro-inverters offer module level monitoring and MPPT optimisation. If a module is shaded, a micro-inverter can adjust its production without affecting the other modules. There are other benefits to module level monitoring, it also gives you the flexibility to design the array with smaller groups of modules on different roof slopes.

You could even use different sizes of panels and different models of modules. Individual module monitoring also helps with troubleshooting problems. However it can be expensive to service micro-inverters. This is because it does require the panel to be removed from the railing. This could require a scaffold or access equipment. It often means a new micro-inverter and/or panel.

What do inverters do?

Inverters do more than convert power from DC to AC they also monitor the modules performance or the performance of the string (A group of panels wired together) and automatically make adjustments to optimise power output. Solar electricity production is constantly fluctuating throughout any given day due to multiple changes in the Solar irradiance, (this is how much sun is hitting the modules) air temperature, shading, and other factors.

Inverters are always monitoring the changing conditions and respond by shifting the balance of voltage and amperage to get the highest possible output from the modules. This is known as Maximum Power Point Tracking (MPPT for short). Most Callidus systems with batteries will have their own MPPT device.

Inverters are also the tools with which PV system owners and technicians can monitor the output and other performance factors of their modules or model strings helping with maintenance troubleshooting and service. Cerbo is a great example of this. Callidus have been able to remotely connect and change simple settings, rectifying a fault code in minutes and saving our customer valuable time and electricity.

What are DC optimisers?

You can check on the performance of your array using a data monitoring system that you can access on your computer or smartphone through the manufacturer’s online software. As you might guess, string inverters can tell you what’s happening only with each string in your array while micro-inverters and DC optimises report on every module in the array. If a module is significantly under performing for no apparent reason you will instantly be aware that something is wrong with it. This is the same for a micro-inverter or if an optimiser has gone offline.

What are Charger inverters?

Charger inverters are needed for all off grid solar systems, because the module of strings from solar panels put out much higher voltage than the batteries can handle. The largest battery banks are rated at 48 volts, while a typical UK home is working off 240 V. The charger inverter regulates the amount and rate of charging that the batteries require at all times. Callidus will make sure the optimum settings are configured to your specific set up and array. It’s a truly bespoke system.

Charger inverters come in many different types, with different ranges, cost and capability. Callidus would highly recommend that if you opt for an off-grid system you have an MPPT charger inverter, which can accept an input voltage from the array that’s higher than its output voltage that goes to the batteries.

What is the difference between micro-inverters and optimisers?

The key difference between micro-inverters and DC optimisers is DC optimisers do not convert DC power to AC power at the module.  They are always used on systems with a string inverter for the power conversion, they do however allow for individual module monitoring and MPPT optimisation.

For any residential solar installation adding optimisers will increase the initial cost, but this needs to be looked at over a longer term as the optimisers will give your panels, better efficiency meaning your using less electricity from the grid.

What does MPPT mean?

Maximum Power Point Tracking (MPPT) capability on a charger inverter is similar to the MPPT with micro-inverters and DC optimisers. In this case the charger inverter constantly monitors the voltage and current of the module strings and adjust the levels as needed to maintain the Maximum Power Point (MPP).

How does an MPPT work?

We don’t live in a perfect world and there are constant adjustments required to keep the system performing. The MPPT Inverter Charger is always managing poor sun conditions, extreme temperature conditions and low battery conditions. MPPT inverter chargers really earn their keep in low light or cloudy weather, when the modules are partially shaded or during any extremes in solar irradiance or temperature. Callidus therefore recommend the MPPT in any solar system.


How can I save money on my electricity bill?

Saving money on energy bills is always a hot topic. Callidus are able to offer a range of solutions to help reduce your energy bills and keep them down. By installing a solar system that is powered by the sun for free and then storing the energy in batteries, you effectively turn your home into a mini power station. Callidus will look at the amount of energy you use, how much you are paying per kW (Kilowatt) and then tailor a system to work for you.

How can I reduce my electricity costs?

Callidus are always trying to help our customers reduce their electricity and energy costs. There are many ways to do this and it is always sensible to make sure you are buying energy efficient products usually measured in A- ratings or AA or A+. The more A’s or +’s the more efficient the product.

On electrical items this means they use less electricity than lower rated items to do the same job. You could also look to change your light bulbs to LED bulbs. LED bulbs can be 10x more efficient than standard halogen or incandescent bulbs adding to that they usually have a much longer lifespan.

Once you put some energy savings in place and then get a Callidus Solar PV array, some solar battery storage and you will be able to really control how much you spend on electricity.

How can I make savings on my energy bills?

Callidus can help you reduce your energy bills by installing a simple but effective solar PV system with battery storage. This is a bit of a hybrid system if you are already connected to the grid. It uses the grid as the back up supply (like a generator in off-grid situations). Callidus will work out a system that best suits your usage and needs.

This will tell us how many panels and batteries you may need to give you a renewable power supply for most of the time. Once your system is installed, you will only be using the grid to back up your system for those dark days of winter or if you have gone for one of the smaller systems, either way your energy bill will be less.

What possible additional charges for items such as evacuation works, concrete pads, trenches, cables etc.?

Are any such items likely to be required for my system? Will there be any other additional costs you have not mentioned (such as scaffolding for example which you specifically exclude in the quote)?

There are only trenching costs if the equipment is not being installed near your existing incoming supply and we have to put cables underground (across a drive or path). Most installations are fine and don’t need additional work. This is identified upon a survey. Scaffolding requirements will be identified upon survey and you can then get an accurate quote from a local scaffolding company based on what you need.

It is so difficult to put a figure on this based on different house types and locations in the country. We can be more helpful to anyone local to our head office in Newton Abbot, but this is limited only as we have various local scaffolders that have worked for our customers.

Are Hybrid or on grid solar and battery systems more expensive?

Hybrid on grid systems are relatively more complex, technically sophisticated and a little more expensive, costing significantly more than a standard on grid system. There are two main types of battery backup systems, DC-coupled and AC coupled. DC coupled are pretty much the main type of installation and set the standard, while AC coupled systems are becoming more common, electricity providers back them because they make it easier to track the solar production.

All Callidus PV systems include one or more inverters that convert the solar generated DC power to AC power for use within the home. This also allows for the additional electricity to be put back into the grid through your electricity company. Off grid systems are a different set up which typically include one or more inverters that receive DC power from the batteries and send AC power to the property.



What are generators used for?

Most off-grid PV systems need or include a generator for backup power as the PV system can rarely meet the demands of the household electrical load. This is usually during the low light days of winter or extended periods of bad weather.

Generators are also useful for equalising batteries and for powering significant loads that would otherwise use a lot more stored power from the batteries and as we know, it is not good for the battery to be drawn down below a certain point as this can cause damage and shorten the life span.

There are many factors to consider when choosing a generator including the size of the battery bank, the household maximum load and AC output of the PV inverter. If a property has a 240-volt load then the generator must also have a 240-volt output.

How do I make sure the generator is the right size?

Generators are typically sized to cover a little more power than the PV inverter’s full charging capacity, plus any household load that may run concurrently with battery charging.

What should I think about if I need a generator?

Most generators are available with remote and auto start features. Remote capability allows you to monitor system functions inside your home and to start and stop the generator remotely. The location of generators is really important as they give off carbon monoxide.

They are usually installed in an outbuilding to remove the risk of deadly exhaust fumes, noise and odours. Sometimes a purpose built shed is best. Please also consider the foundation the Generator will sit on as larger generators can vibrate and it is these vibrations that can disturb your day to day living.