Is Solar Energy Reliable? Your Guide to The Facts & Myths

As specialists in renewable energy, one of the more common questions we hear from homeowners or businesses considering a solar PV installation is, “Is solar energy reliable?” – especially here in the UK, where a sunny day can sometimes seem like a rarity.

Well, the short answer is yes. Thanks to innovations in solar panel design and the underlying technology, solar energy is a much more realistic option for temperate climates like the UK than it was ten or twenty years ago. But, with myths about solar power’s unsuitability persisting, it’s a good idea to understand the details, define what reliability really means, and explore what use cases solar PV can effectively address in the UK.

This guide is designed to provide you with a better understanding of the reliability and durability you can expect from a modern solar panel installation, and the ways in which you can maximise the impact of your investment in solar. In this 10-minute read, we’ll take a look at key questions, including:

• What makes an energy source reliable?
• Are solar panels reliable in typical UK weather conditions?
• How reliable is solar energy at night or during low-light periods?
• How can battery storage enhance solar reliability?
• What’s the expected lifespan of solar panel systems?
• What are the common myths about solar reliability, and the realities?
• When might solar panels not be the best option?

What makes an energy source reliable?

Before getting into the details, let’s define what “reliability” means as it applies to an energy source. Broadly speaking, reliability is a combination of four factors:

• Availability: Is the energy source there when you need it?
• Consistency: Does it provide a steady, uninterrupted supply of power?
• Sufficiency: Is the total power output enough for your needs?
• Scalability: Can the energy source meet future demands?

Traditional energy sources (coal, oil, gas and nuclear), which have been the backbone of our energy supply for decades, are generally considered reliable in that they fulfil each of those four criteria well. However, they come with their own set of issues, which impact how reliable we can consider them to be long-term.

Fossil fuels (coal, gas and oil) are finite, and the process of extracting them is increasingly costly and environmentally damaging. Geopolitical events can also significantly impact trading prices, which makes energy costs unpredictable. And the centralised model of large power plants (including nuclear) can be vulnerable to widespread outages.

Solar energy, on the other hand, offers a different reliability profile:

• The sun provides an essentially unlimited energy source.
• Solar generation varies with day/night cycles and weather. However, this intermittency is predictable to an extent.
• Solar installations can be widely distributed and sited close to the point of need, reducing reliance on a single point of failure.

So, while solar panel output isn’t constant in the same way as a gas power plant, modern technology and system design have made it a highly dependable option – with a much lower environmental impact than traditional methods of generating energy.

Are solar panels reliable in typical UK weather conditions?

It’s a common misconception that the UK isn’t sunny enough for solar panels to be worthwhile. In fact, the total hours of sunlight are similar to those in Germany, already a world leader in solar adoption. Of course, yield will always be higher in summer versus winter, but that can be factored into system design. The key figure is the annual yield, which is substantial enough in the UK to make solar a viable option.

The key factor to remember is that solar photovoltaic (PV) panels work on light, not necessarily direct sunlight. Even on overcast days, significant amounts of light still penetrate the clouds, so while output will be lower than on a bright sunny day, generation doesn’t stop. Modern solar panel technology has focused on improving the effectiveness of panels in capturing this diffused or scattered light.

Another advantage the UK has is its cooler temperatures – yes, you read that correctly. Most solar panels operate more efficiently in cooler temperatures – excessive heat can reduce their output. So while the total output of a solar system may be lower in the UK than, say, the Middle East, the increased efficiency with which the panels operate means the gap is not as large as you might imagine.

How reliable is solar energy at night or during low-light periods?

There’s no getting around the fact that solar panels do not generate electricity if there’s no light! This is where system design and complementary technologies come into play, with three main ways that solar energy systems address the lack of generation during night or low-light conditions:

System type	How it works	Is it reliable?
Grid Connection (Grid-Tied Systems)	During the day, you use the solar energy you generate. If you produce more than you need, it can be exported to the grid. When solar panels aren’t producing power, you automatically draw electricity from the grid as usual.	Extremely reliable, as you have the grid as a 100% backup. Currently, the most common setup in the UK for homes and businesses.
Battery storage (Hybrid or off-grid systems)	Solar batteries store the excess electricity your panels generate during the day. This can then be used at night, during peak demand hours (when grid electricity might be more expensive), or during a power cut (if the system is configured for backup power).	Highly reliable. Batteries provide energy independence and bridge the gap when solar panels aren’t generating. Becoming more common in the UK as battery storage systems have become more accessible/economical.
Off-grid systems	These systems are not connected to the national grid. They rely entirely on solar generation and battery storage to meet all energy needs.	Variable in terms of reliability. Depends on system sizing – ensuring enough panel capacity to generate sufficient power and enough battery storage to cover periods of no sun. Fully off-grid systems are rare in the UK.

How can battery storage enhance solar reliability?

Battery storage systems transform your solar PV installation from an intermittent daytime source into a consistent and controllable 24/7 supply. By adding a BESS to your solar PV system, you unlock several benefits that directly boost reliability:

• Maximising self-consumption: Batteries store your surplus solar energy that would otherwise be exported to the grid (often for a lower feed-in tariff rate). You can use this stored, free energy during the evening or night, reducing your reliance on grid power.
• Peak shaving: Electricity tariffs are often higher during peak demand hours (e.g., early evening). With a battery, you can use your stored solar power during these times, avoiding expensive peak charges and further lowering your bills.
• Grid trading: New legislation allows UK businesses to profit from intelligent grid trading with battery energy storage systems, selling your stored energy back to the grid when demand (and the unit price) is high.
• Backup power: Certain battery systems can be configured to provide backup power if the grid goes down, so essential equipment or infrastructure can keep running with no disruption to business as usual.
• Reduced intermittency: BESS helps smooth out fluctuations inherent to solar generation by discharging stored energy when panel output temporarily dips, ensuring a more stable supply to your property.

What’s the expected lifespan of solar panel systems?

Modern solar panels are incredibly robust. Most Tier 1 manufacturers offer a lifespan of 25 to 30 years, and many continue to generate electricity well beyond this period. When comparing the panels available, you’ll usually see two types of warranty:

• Product Warranty (or Materials Warranty): This covers defects in materials and workmanship, typically for 10-15 years, with some premium brands offering up to 25 years.
• Performance Warranty (or Power Output Warranty): This guarantees that the panels will maintain a certain percentage of their original output capacity over time. A common standard is a guarantee of at least 80-85% of nominal power output after 25 years.

It’s true that solar panels experience a slight, gradual decline in efficiency over their lifespan (known as degradation). However, the rate of degradation for modern panels is very low, typically around 0.5% to 0.8% per year. This means that even after two decades, your panels will still be operating at a high percentage of their initial capacity.

Solar PV systems are remarkably low-maintenance, and in the UK, natural rainfall often keeps panels sufficiently clean. In some cases (e.g., very dusty areas or near trees with heavy bird droppings), occasional cleaning might be beneficial to maintain optimal performance, but it’s not usually a frequent requirement.

What are the common myths about solar reliability, and the realities?

Several myths about solar reliability persist, especially concerning the effectiveness of solar panel installations in the UK’s often cloudy, rainy climate. Let’s break down a few of them with clear facts:

Myth: “Solar doesn’t work in the UK because it’s not sunny enough.”

Reality: This is probably the most common misconception. The UK receives ample daylight throughout the year to make solar a viable and effective energy source. As we mentioned above, today’s solar panels are highly efficient in capturing diffused light, which means they keep generating even on overcast days.

Myth: “Solar energy is too weather-dependent to be truly reliable.”

Reality: Solar output does vary with the weather (more on sunny days, less on cloudy days), but this variability is predictable. Solar system designers use historical weather data and sophisticated modelling to accurately estimate annual energy production for a specific location. And as we’ve seen, when integrated with the grid or a battery storage system, this intermittency is eliminated.

Myth: “Solar panels don’t work if it’s cloudy.”

Reality: Panels do work on cloudy days, just at a reduced output compared to bright, clear days. Even on a heavily overcast day, solar panels can typically produce 10-25% of their rated capacity. Over a year, the energy generated during these less-than-perfect conditions still contributes significantly to overall energy savings.

Myth: “Solar panels are fragile and require a lot of maintenance.”

Reality: Solar panels are engineered to withstand extreme weather like hail, snow, and high winds, and they have no moving parts, which means there’s very little that can mechanically fail. Maintenance is minimal: occasional cleaning (even less of an issue in rainy climates like the UK) and periodic inspections, as with any infrastructure.

Myth: “You’ll have no power at night or during blackouts with solar.”

Reality: Partially true. For standard grid-tied solar systems (without batteries), your system will automatically shut down during a power cut for safety reasons (to prevent sending power back to the grid while workers are trying to fix it). However, if you have a solar system combined with a BESS (and it’s configured for backup power), you can maintain power to essential circuits during a blackout.

When might solar panels not be the best option?

As a leading specialist in renewable energy solutions, we’re naturally huge advocates for solar energy. But, we’re engineers – and we recognise that solar PV is not a magic bullet. Naturally, there are cases where solar isn’t the best option, and we advise our customers to look to alternative energy sources. Here are some of the factors that could mean solar power isn’t the right choice for your home or business:

Even taking the above points into account, the pace of development in solar PV and associated technologies continues to accelerate. That means that, with new cell and solar panel types coming onto the market, alongside complementary solutions such as improved battery storage, we’re able to design systems to solve more and more use cases every year. And if your only barrier to entry is the suitability or structural integrity of your roofspace, we can help with roof refurbishment or replacement.

The key is to talk to an expert to find out what’s possible. Your premises may be more suited to solar generation than you think. At JLM, we have extensive experience designing solar PV installations of all sizes, which overcome logistical, structural or siting challenges to deliver highly efficient systems.

If you’re looking to make the switch, the ideal first step is to book our free remote audit, where we’ll review your current energy use in detail and propose the most cost-efficient solution based on your available space and budget. This can include zero-upfront-cost models, which allow you to implement solar energy without capital expenditure. Contact one of our expert consultants to book your free remote energy audit today.