The Ultimate solar glossary: Terms every homeowner should know

Thinking about installing solar panels at home? You’ve probably come across terms like kWp, kWh, inverter, self-consumption and feed-in tariff. They might sound a little technical at first, but once you understand what they mean, choosing and getting the most out of a solar PV system becomes much easier.

Whether you’re just starting to explore solar energy or you’re already comparing PV systems for your home, this guide breaks down the most important solar terms in simple, everyday language.

And because solar systems work a little differently depending on where you live, we’ll also cover some of the terms you’re likely to come across when installing solar in Malta.

Solar terms at a glance

Here are some of the most common terms you’ll encounter when researching solar energy.

1. Solar PV basics

What is photovoltaic (PV)?

Photovoltaic, usually shortened to PV, is the technology used to convert sunlight directly into electricity.

Solar panels contain photovoltaic cells. When sunlight hits these cells, they generate electricity in the form of direct current (DC). An inverter then converts this into alternating current (AC), which can be used by the appliances in your home.

In simple terms:

Sunlight → Solar panels → DC electricity → Inverter → AC electricity → Your home

This DC-to-AC conversion is the foundation for almost everything else in this guide, so it’s worth keeping in mind as you read on.

What is a solar panel?

A solar panel, also called a PV panel or photovoltaic panel, is made up of many photovoltaic cells that work together to generate electricity from sunlight.

The number of panels you need depends on several factors, including your electricity consumption, available roof space, panel power and the amount of sunlight your property receives.

What is a solar cell?

A solar cell is the individual unit inside a solar panel that converts sunlight into electricity. A single panel contains multiple solar cells connected together to produce a useful amount of electrical power.

What is a solar array?

A solar array is simply a group of solar panels connected together as part of a PV system. So, while you might casually refer to all the panels on your roof as “solar panels”, the complete group is known as the solar array.

What is DC?

DC or direct current is the type of electricity generated by solar panels. The electricity produced by your panels is initially DC. Because most homes use AC electricity, the DC electricity needs to pass through an inverter before it can be used by your household appliances.

What is AC?

AC or alternating current is the type of electricity used by the electrical system in your home. Your solar panels produce DC electricity, while your household appliances generally use AC electricity. The inverter converts the electricity from DC to AC so you can use it around your home.

2. Understanding solar power and electricity

Some of the most confusing solar terms are actually measurements of power and energy. The good news is that the difference is quite straightforward.

What is a watt (W)?

W is a unit used to measure power. For example, an appliance might have a power rating of 1,000 watts, or 1 kilowatt.

What is a kilowatt (kW)?

A kW is equal to 1,000 watts. These are used to describe the power capacity of equipment such as solar inverters or appliances. For example, a 5 kW inverter can handle a certain amount of electrical power at a given moment.

What is watt-peak (Wp)?

Wp describes the peak power output of a single solar panel under standard testing conditions. In fact, you may see panels described as, for example, 400 Wp or 450 Wp.

Kilowatt-peak (kWp) is the peak power rating of a complete solar PV system or group of panels. For instance, a system made up of ten 450 Wp panels would have a total panel capacity of 4.5 kWp.

It’s important to remember that kWp describes the rated power capacity of the panels. It doesn’t mean the system will continuously generate that amount of electricity throughout the day.

What is a kilowatt-hour (kWh)?

kWh measures energy, in other words, how much electricity is generated or consumed over a period of time. Your electricity consumption is normally measured in kWh, so if an appliance uses 1 kW of power for one hour, it uses 1 kWh of energy.

kWp vs kWh: What’s the difference?

This is one of the most important distinctions to understand when comparing solar systems.
kWp tells you how much power your solar panels are designed to produce at their rated peak, while kWh tells you how much electricity is actually generated or consumed over time.

So, a 5 kWp solar PV system doesn’t necessarily generate 5 kWh every hour. Its actual generation varies throughout the day and year depending on factors such as sunlight, orientation, shading and weather conditions.

What are peak sun hours?

Peak sun hours describe the amount of sunlight available for solar energy production. They don’t simply mean the number of hours the sun is in the sky. Instead, they represent the equivalent number of hours of sunlight received at a standard intensity. This helps solar professionals estimate how much
electricity a PV system could generate.

Solar irradiance refers to the amount of solar power reaching a given surface. In other words, how much sunlight is available for your panels to convert into electricity.

3. The main components of a solar PV system

As mentioned earlier, a solar inverter converts the DC electricity produced by your solar panels into AC electricity that your home’s electrical system can use. Depending on the type, it can also manage electricity flowing between your solar panels, home, battery and the electricity grid. The inverter is one of the key components of any PV system, and there are a few common configurations:

• Hybrid inverter – manages electricity from multiple sources (solar panels, home, battery and grid), making it particularly useful for systems that include battery storage.
• String inverter – connects a group, or “string”, of solar panels to a single inverter.
• Microinverter – a small inverter installed at each individual panel, rather than one central inverter handling multiple panels. Useful in certain roof designs or where panels receive different levels of sunlight.
• Power optimiser – works alongside individual panels to optimise their output before it reaches the inverter, useful where panels have different orientations or face partial shading.

Here is some further information about hybrid and standard inverters.

4. Solar batteries and energy storage

A solar battery stores electricity so it can be used later. For example, your panels may generate more electricity than your home needs during the day, but instead of sending all of that excess electricity to the grid, a battery can store some of it for use later, helping increase the amount of your solar electricity that you use yourself.

Battery capacity vs. battery power

Battery capacity, measured in kWh, is the amount of energy a battery can store. A battery with a 10 kWh capacity can store up to a certain amount of electrical energy, subject to its usable capacity and operating limits.

Battery power, measured in kW, describes how quickly the battery can deliver or receive electricity.

What is depth of discharge (DoD)?

DoD describes how much of a battery’s stored energy can be used before it needs to be recharged. If a battery has a 10 kWh capacity and its recommended usable depth of discharge is 90%, around 9 kWh would be available for use.

What is state of charge (SoC)?

State of charge (SoC) tells you how much energy is currently stored in your battery, usually expressed as a percentage. A battery at 100% state of charge is fully charged, while one at 20% has much less energy available.

What is a battery cycle?

A battery cycle refers to a complete charge and discharge cycle of a battery. Battery manufacturers use cycle information when describing the expected lifespan of battery storage systems.

5. Using solar electricity at home

Understanding what happens to the electricity your panels generate is just as important as understanding the panels themselves.

Self-consumption vs. self-sufficiency

These two terms sound similar but measure different things:

Self-consumption is the solar electricity you generate and use directly in your home — for instance, while your washing machine or air conditioner is running. The more of your generated solar electricity you use yourself, the higher your self-consumption.

Self-sufficiency describes how much of your home’s total electricity needs are met by your own solar generation, rather than electricity imported from the grid.

Import and export

Import is the electricity your home takes from the grid, such as when your panels aren’t producing enough to meet demand.

Export is electricity your PV system generates but doesn’t use, which is instead sent to the electricity grid. Depending on the applicable scheme, exported electricity may be eligible for payment.

6. Solar schemes and exporting electricity in Malta

If you’re considering solar panels in Malta, you’ll probably come across a few terms relating to government schemes, grid connection and payments for exported electricity.

What is a feed-in tariff?

A feed-in tariff (FIT) is a payment made for eligible electricity generated by a PV system and exported to the electricity grid. The exact arrangements, rates, eligibility criteria and available allocations depend on the applicable scheme. In Malta, feed-in tariffs for solar PV are administered by the Regulator for Energy and Water Services (REWS). Because these schemes can change, it’s always worth checking the latest official information before making decisions based on a particular tariff.

What is a PV grant?

This is financial support that may be available towards the cost of an eligible renewable energy system. Naturally, eligibility requirements and amounts can change from one scheme or year to another.

If you’re planning to install solar, make sure you check the current scheme requirements before purchasing or installing equipment.

Grid connection, REWS and Enemalta

Grid connection is the process of connecting your solar PV system to the electricity distribution network. In Malta, applications involving PV systems and feed-in tariffs go through the relevant regulatory and grid-connection processes, involving both REWS (the Regulator for Energy and Water Services, which administers renewable energy schemes and feed-in tariffs) and Enemalta plc (Malta’s electricity distribution and supply company, which connects installations to the network).

7. Understanding a solar quote

Once you start comparing solar systems, you’ll see many of the terms above appearing on quotations. Here’s what some of the most important ones mean in practice.

• System size — usually expressed in kWp, this tells you the total peak capacity of your solar panels. A bigger system isn’t automatically better, while the right size depends on factors such as your electricity consumption, available roof space and how much electricity you want your system to generate.
• Estimated annual generation — an estimate, in kWh, of how much electricity your system could generate over a year. It’s an estimate rather than a guarantee, since generation is affected by weather, shading, orientation and system performance.
• Panel efficiency — how effectively a panel converts the sunlight it receives into electricity. Higher efficiency can be particularly useful when roof space is limited, as more electricity can potentially be generated from a given area.
• Warranty — a solar system can come with several types: a product warranty, which covers defects in the equipment itself), a performance warranty, covering the panel’s expected electricity-generating performance over time, as well as an installation warranty, which may cover aspects of the installation work. It’s worth checking exactly what is covered, for how long and by whom.
• Payback period — the estimated time it takes for the financial benefits of a solar installation to recover its initial cost. This depends on factors such as system price, electricity consumption, generation, electricity prices, exported electricity and any applicable incentives. Since these factors can change, treat a payback estimate as an indication rather than a guarantee.

8. Solar performance: what affects how much electricity you generate?

Two homes can have similarly sized PV systems but generate different amounts of electricity. Here’s why.

Shading occurs when something like a tree, building, chimney or wall blocks sunlight from reaching your panels. Even partial shading can affect generation, which is why the position and layout of your panels matter.

Orientation refers to the direction your panels face, which affects how much sunlight they receive throughout the day and therefore how much electricity they can generate.

Tilt is the angle at which your panels are installed. The ideal angle depends on factors such as location, roof design and desired system performance.

Panel degradation is the gradual reduction in a panel’s electricity-generating capacity over time. Panels are designed to operate for many years, but output naturally decreases as they age.

Performance ratio is a way of assessing how effectively a PV system converts available solar energy into usable electricity after accounting for system losses. It can give a more realistic picture of performance than looking at panel capacity alone.

9. Solar maintenance and lifespan

One of the biggest advantages of a solar PV system is that there are no moving parts in the panels themselves, but that doesn’t mean you should completely forget about your system once it’s installed.

Do solar panels need cleaning?

Solar panels can accumulate dust, dirt and other debris, which can affect the amount of sunlight reaching the panel surface.

How often cleaning is needed depends on the location and conditions around your property.

• Cleaning: Panels can accumulate dust, dirt and debris, which can affect the amount of sunlight reaching the panel surface. How often cleaning is needed depends on the location and conditions around your property.
• Lifespan: Panels are designed to operate for many years, with output gradually decreasing over time. The lifespan of the complete system can vary, since components like panels, inverters and batteries have different expected operating lives.
• Monitoring: A solar monitoring system lets you track how your PV system is performing, including current generation, consumption, grid import/export, battery charge level and historical generation. Monitoring helps you understand both system performance and your own usage patterns.

Take a look at this guide on how to maintain your PV system.

How GO Energi can help

Understanding the terminology is the first step but putting it into practice on your own roof is where it helps to have an experienced team behind you. Here’s how we support homeowners at each stage:

• Site assessment and system design: we evaluate your roof space, orientation, shading and electricity consumption to design a system sized correctly for your home, not just the biggest system that fits.
• Supply and installation: from panels and inverters to battery storage, we source and install equipment suited to your budget and goals, backed by clear product, performance and installation warranties.
• Grid connection and scheme support: we help manage the paperwork and processes involved with REWS and Enemalta, including feed-in tariff applications and eligibility checks for current grants and schemes.
• Battery storage integration: if you want to increase your self-consumption or prepare for outages, we can advise on and install battery systems sized to your household’s usage patterns.
• Monitoring and aftercare: once your system is live, we help you set up monitoring so you can track generation, consumption and performance — and we’re on hand for maintenance and servicing over the system’s lifetime.

Discover more about GO Energi.

Solar might come with plenty of technical terms, but choosing the right system doesn’t have to be complicated.

The key is to look beyond the number of panels and understand how the complete system will work for your home, your electricity consumption and your everyday routine.