Solar PV Explained

Solar PV is about more than choosing a panel.

The roof, system size, inverter, mounting method, shading, grid connection and what you plan to add later can all affect how well the installation works.

Energy Flow Hub is designed to help you understand the complete solar PV system before you start comparing products, quotations or installers.

Is Your Home Suitable for Solar?

Most homes can be assessed for solar PV, but some roofs are better suited than others.

The main things to consider are:

roof orientation
roof pitch
shading
usable roof area
roof condition
structural suitability
chimneys, dormers and rooflights
whether panels would need to be split across more than one roof face

A south-facing roof can be ideal, but it is not the only option.

East- and west-facing roofs can still generate useful amounts of electricity and may sometimes spread generation more evenly across the day.

The important question is not simply whether a roof faces south.

It is whether the complete roof and system design make sense for the property.

Explore Solar Suitability

How a Solar PV System Works

Solar photovoltaic panels generate DC electricity when exposed to daylight.

That electricity passes to an inverter, which converts it into AC electricity that can be used by the home.

At any moment, the electricity generated may be:

used directly by appliances in the house
used to charge a battery
used to charge an electric vehicle
exported to the electricity grid

The balance changes throughout the day as solar generation and household demand rise and fall.

A well-designed system therefore needs to consider not only how much electricity the panels can generate, but also how that electricity is likely to be used.

Solar Is a System, Not Just Panels

The panels are the most visible part of a solar installation, but they are only one part of it.

A typical solar PV system can include:

Solar Panels: Convert sunlight into DC electricity.
Inverter: Converts DC electricity from the panels into AC electricity for the home.
Mounting System: Secures the panels to the roof using rails, hooks, brackets or another suitable mounting method.
DC Cabling: Connects the panels to the inverter.
AC Connection: Connects the inverter to the electrical installation.
Electrical Protection: Protective devices and isolators form part of the overall electrical design.
Metering: Allows generation, import and export to be measured where required.
Export Control: Some installations require equipment to limit how much electricity can be exported to the grid.

The quality and suitability of these less visible components matter just as much as the panel brand printed on the quotation.

How Big Should a Solar PV System Be?

Solar systems are normally described by their installed capacity in kilowatt peak — kWp.

For example:

10 × 450 W panels = 4.5 kWp

But a 4.5 kWp system does not continuously produce 4.5 kW.

Actual output changes throughout the day and year depending on factors such as:

sunlight
temperature
roof orientation
roof pitch
shading
panel layout
inverter design

The right array size may also depend on:

available roof area
annual electricity use
daytime consumption
battery storage
EV charging
future heat-pump demand
export limitations
budget

There is no universal number of panels that every home should have.

The aim should be to design a system around the property, available roof space and expected energy use.

kW, kWp and kWh: What Is the Difference?

These terms are often confused.

kWp — Kilowatt Peak: The rated capacity of the solar array under standard test conditions.
kW — Kilowatts: The amount of power being generated or used at a particular moment.
kWh — Kilowatt Hours: The amount of energy generated or consumed over a period of time.

A 5 kWp solar array may generate thousands of kWh over a year, but its instantaneous output will constantly change.

Understanding the difference becomes particularly important when comparing:

solar array size
inverter size
battery capacity
battery power
EV charging
household demand

Solar Panels: What Actually Matters?

Panel wattage is useful, but it is not the only specification worth looking at.

When comparing solar panels, consider:

panel dimensions
rated output
efficiency
construction
product warranty
performance warranty
degradation
appearance
suitability for the available roof space

A physically larger panel may have a higher wattage but may not always produce the best layout on a particular roof.

Sometimes a slightly smaller module allows more panels to fit around dormers, rooflights or other obstructions.

That is why panel choice should be considered as part of the array design, rather than simply selecting the panel with the largest number on the data sheet.

The Inverter Matters Too

The inverter is one of the most important parts of a solar PV system.

It converts the DC electricity generated by the panels into AC electricity that can be used around the home.

Different systems may use:

string inverters
hybrid inverters
microinverters

The choice can affect:

system layout
battery options
shading performance
multiple roof orientations
monitoring
future expansion

Why Isn't the Inverter Always the Same Size as the Solar Array?

A common assumption is that a 6 kWp solar array must have a 6 kW inverter.

That is not necessarily the case.

Solar panels only reach their rated output under particular conditions, and their output changes constantly.

It can therefore be perfectly normal for an inverter to have a lower AC rating than the total DC panel capacity.

The correct relationship depends on the:

solar array
inverter
orientation
expected generation profile
manufacturer limits
grid connection

A bigger inverter is not automatically a better inverter.

Understand Inverter Sizing

Hybrid Inverter or Standard Solar Inverter?

A standard solar inverter converts electricity from the PV array for use in the home or export to the grid.

A hybrid inverter can also provide a DC connection for compatible battery storage.

That does not automatically make a hybrid inverter the right choice for every property.

But if battery storage is likely to be added later, the inverter decision should be made with that future plan in mind.

Solar now and battery later is possible, but the choices made during the first installation can influence how the battery is eventually connected.

Roof Mounting Systems Matter

The mounting equipment may be largely hidden after installation, but it is a fundamental part of the system.

Different roofs require different approaches.

Examples include:

Tiled Roofs: Roof hooks are normally fixed into the roof structure, with rails supporting the solar panels above the tiles.
Slate Roofs: Specialist fixings are required to avoid relying on the slate itself for support.
Flat Roofs: Systems may use ballasted or mechanically fixed frames to achieve the required panel angle.
Standing-Seam Metal Roofs: Special clamps can attach to suitable seams without penetrating the roof covering.
In-Roof Solar: Panels replace part of the conventional roof covering rather than sitting above it.

Other details can include:

rail systems
hook extensions
brackets
clamps
cable management
bird protection

The mounting system should suit both the roof covering and the building structure.

Orientation, Pitch and Shading

The position of the panels affects how and when electricity is generated.

Orientation

South-facing arrays can deliver strong overall annual generation.

East- and west-facing arrays can generate more electricity earlier and later in the day.

Roof Pitch

The angle of the panels influences how much sunlight reaches them throughout the year.

Shading

Potential sources include:

trees
chimneys
dormers
neighbouring buildings
aerials
roof structures

Even relatively small areas of shade can affect parts of an array depending on the system design.

Technologies such as:

multiple MPPTs
power optimisers
microinverters

can sometimes help manage more complicated layouts.

They are not automatically necessary on every installation.

Generation, Self-Consumption and Export

Generating electricity is only part of the story.

What matters next is what happens to it.

Example

Imagine a solar system is generating 3 kW.

If the house is using 1 kW, the remaining 2 kW has to go somewhere.

Depending on the system, that surplus may:

charge a battery
charge an EV
be exported to the grid
be limited if export controls apply

The proportion of solar electricity that is used directly within the property is often referred to as self-consumption.

Increasing self-consumption can increase the value of the electricity generated, but it does not mean exporting electricity is necessarily a bad thing.

The right balance depends on:

electricity tariffs
export payments
battery strategy
EV charging
household demand

What Happens to Excess Solar Electricity?

In a simple system without a battery:

Solar generation → household demand → grid export

With battery storage:

Solar generation → household demand → battery → grid export

The exact behaviour depends on the equipment and control strategy.

The battery may charge when excess solar is available and discharge later when household demand exceeds generation.

With an EV charger capable of solar-aware charging, surplus generation may also be directed towards the vehicle.

Understanding these energy flows is one of the reasons it helps to think about the whole home, rather than each technology separately.

Solar PV and Battery Storage

You do not need battery storage to install solar PV.

And you do not necessarily need to install the battery at the same time as the panels.

Battery storage can allow more solar electricity to be retained for use later in the day, but adding a battery introduces additional design decisions.

These include:

battery capacity
battery power
AC coupling
DC coupling
inverter compatibility
backup capability
tariffs
future expansion

If a battery is likely to be added later, it is worth considering that before the solar inverter is chosen.

Explore Battery Storage

Solar PV and EV Charging

An electric vehicle can be a significant electrical load.

Solar PV can contribute towards EV charging, particularly when the vehicle is at home during daylight hours.

But a 7 kW EV charger does not mean that 7 kW of solar electricity is always available to charge the vehicle.

Charging depends on:

current solar generation
household demand
charger settings
battery behaviour
electricity tariff
minimum charging requirements

Some chargers can dynamically adjust charging power based on available surplus solar generation.

A solar, battery and EV system should therefore be considered as a connected energy system rather than three completely separate products.

Explore EV Charging

Planning Now for Future Upgrades

You do not need to install every technology at once.

But it can be useful to think ahead.

For example, you might install:

solar now and a battery later
solar now and an EV charger later
solar and battery before a future heat pump
solar now with whole-home backup added later
one solar array now and additional panels in the future

Future plans may influence decisions about:

inverter type
inverter capacity
cable routes
equipment location
consumer-unit arrangements
CT clamp positions
electrical capacity
grid applications

Future-proofing does not always mean spending more money.

Sometimes it simply means avoiding a decision now that unnecessarily limits the next stage.

Explore Whole-Home Energy

Grid Connection and Export

A grid-connected solar PV system operates alongside the electricity network.

When the home requires more electricity than the solar system is producing, electricity can be imported from the grid.

When the system produces more electricity than the property is using or storing, surplus electricity may be exported.

Depending on the size and design of the system, grid-connection requirements may involve:

G98
G99
export limitation
G100 compliant export control
DNO notification or approval

The exact requirements depend on the installation.

For homeowners, the important point is that the grid connection can influence the system design, particularly on larger installations or where batteries and other generation are involved.

Smart Export Guarantee

Eligible small-scale generators may be able to receive payment for electricity exported to the grid through a Smart Export Guarantee tariff.

Export rates and conditions vary between suppliers.

This means the value of surplus electricity can depend not only on the solar system, but also on:

the export tariff
battery behaviour
household consumption
EV charging
when electricity is exported

Tariffs are increasingly becoming part of the wider home-energy strategy.

What Should a Good Solar Proposal Tell You?

A quotation should contain enough information for you to understand what is actually being proposed.

Useful information includes:

solar panel manufacturer and model
number of panels
total array capacity in kWp
inverter manufacturer and model
inverter rating
predicted annual generation
roof orientation
shading assumptions
mounting system
battery compatibility where relevant
expected export
warranties
monitoring arrangements

Two quotations showing the same number of panels may still represent very different system designs.

The more you understand the specification, the easier it becomes to compare them properly.

Solar Tools & Calculators

Energy Flow Hub is developing practical tools to make solar PV easier to understand.

Solar Generation Calculator: Estimate how much electricity a solar array might generate.
Solar Array Size Calculator: Explore panel quantity, panel wattage and total system capacity.
Inverter Sizing Tool: Understand the relationship between solar-array capacity and inverter power.
Solar String Calculator: Explore voltage, current, MPPT and inverter limits when configuring panel strings.

Explore Solar Tools

Explore Solar PV

There is much more to solar PV than panel wattage.

Explore our guides covering:

solar panels
inverters
system sizing
roof mounting
shading
optimisers
microinverters
strings
batteries
EV charging
export
grid connection
costs and payback

The more you understand the system, the easier it becomes to make sense of the products and quotations being offered.

Planning Solar PV?

Start by understanding the property, the roof and how you want to use the electricity.

Then consider the equipment.