Before you commit to solar panels, it’s important to ask the right questions to make sure you’re getting the best system for your property and budget.

This guide will walk you through the key questions careful, informed homeowners ask their preferred solar panel installer before accepting a quote.  

Generating your own clean, free electricity is an exciting prospect, and we want to make sure islanders are handed the right information before making big investments of this scale.

Understand things upfront and you’ll be in a much stronger position to make an informed decision and get the most from your solar installation in Guernsey.

Please be aware the Guernsey Electricity do not currently install solar panels in Guernsey. 

Jump to the list of questions to send your installer, or read on to understand things a bit better. 

1. Can you explain how solar panels and battery systems work together?

Don’t get bogged down in technical jargon. As it’s a big initial outlay, it’s best to have a clear understanding from the start.

Please also be aware that inverters and batteries can be sensitive to both extreme heat (such as during summer heat waves) and damp.  

• Solar photovoltaic panels: known in the industry as ‘solar PV’, in Guernsey these are often installed on south-facing roofs to capture sunlight at its longest exposure. The solar panels covert solar energy into ‘direct current’ (DC) electricity. An ‘inverter’ installed in an indoor area or garage (often in the same location as your battery storage) then converts this into ‘alternating current’ (AC) electricity, the standard power that runs your kettle, TV and fridge, etc.
• Home battery storage: Solar panels only produce power when the sun is shining. If you don’t use it, you lose it*. And if you’re relaxing on the beach while your solar panels are busy back home generating electricity, your solar panel system may switch off (more on this below). A home battery will store that excess daytime power, much like a power bank for recharging your phone. Instead of letting that free energy slip through your fingers, it stores that power for later, so when you’re using more electricity at home, you can use your own stored power instead of paying the ‘normal’ (higher) grid rate.

*Unless you’re set up on a ‘Buy Back’ tariff following an ‘EE40’ submission to Guernsey Electricity. Confused? We’ll talk about this later.

Find out more about battery storage here.  

Ask your installer: Where will you install the inverter [and battery system if relevant] in my home, and do those chosen locations meet Guernsey’s specific building and safety regulations for temperature and ventilation?

2. How many solar panels do I need to install?

Don’t oversize. Panel count should match your core use - the more panels you install, the more it’ll cost you to install, maintain and replace.

Your installer should first calculate the right system size based on how much electricity your property uses, and also when you use it.

For example, if your system generates most power at midday but you use most electricity at 7pm, a large system may not benefit you as much as you’d expect (without any battery storage). A good installer will look at your unique usage patterns throughout the day, rather than just rely on annual usage data, and make sure your system is sized properly to match how you actually live.

You can also check this out for yourself ahead of getting a quote. Just give Guernsey Electricity a ring on 01481 200700 Monday to Friday between 9am and 5pm, as they can pull your exact historical data* and tell you how many units (in kilowatt-hours/kWh) you use annually – particularly during winter when you’ll likely use the most power.  

Oversizing your solar panel system, particularly without a battery, can be a waste of money as much of it will go unused.

Your panel count should reflect how much electricity you use today. But, if you know that’s likely to change, it can be sensible to go slightly bigger. For example, installing an electric vehicle charger, a hot tub, or even upgrading to an induction hob, will all add to your future power demand and bill. 

Guernsey homes rely heavily on unique local heating types and have different tariff structures to the UK, which means an ‘average UK home estimate’ is likely to be inaccurate and unverified against your actual historical data. This information is very easy to get from Guernsey Electricity. Without it, there’s a risk you might overpay for panels you don’t need (unless you’re planning to get a battery storage system), or undersize your system entirely.

*Technology is great, but sometimes things don’t go to plan. Especially if your meter depends on signal, as some properties (depending on location) have patchy data transmission. Please ask Guernsey Electricity: “Is my meter communicating properly, and is my usage data accurate enough for a solar installation quote?” If the data isn’t available an electrical contractor may be able to install a logger to track your electricity use for a period of time.

Ask your installer: Before providing a quote, please cross-reference the proposed system design with my actual electricity consumption data from Guernsey Electricity and avoid using an ‘average UK home’ template.

3. Can I use my solar installation to offset electric heating?

The quick answer is no - and this is rarely explained clearly. 

• Solar panels connect to your ‘light and power’ meter, which supplies your everyday electricity (lighting, appliances, sockets).
• If your home has a separate electric heating meter (such as Superheat or Heatpump), your heating is billed separately.

That means your solar panels can only offset your light and power, not your electric heating. It can’t be shared across both meters because a solar system is physically wired into a single circuit. The electricity it generates can only flow through one meter, not be split between two.

The main exception is if you use an overnight storage heating system that runs from your light and power meter. This uses one of the cheapest heating tariffs in Guernsey by charging up overnight on lower-cost electricity. Solar can contribute indirectly, but this setup is different from most electric heating systems.

It’s also worth noting that solar panels generate least electricity in winter when heating demand is highest, so even if everything were connected, solar alone wouldn’t meet most islander's heating needs without significant battery storage.

Ask your installer: As solar power cannot reduce electric heating bills, based on how my home is metered, can you explain how my solar system will help offset my overall electricity use?

4. Should I get a home battery system?

If you can, it’s highly recommended. Every unit you store and use yourself is worth far more than exporting (or losing) it, meaning you'll enjoy a premium return for the exact same electricity.

It's like being paid over 60% more for the same thing. You’ll ‘earn’ much more saving 27.77p per unit during the higher ‘normal rate’ 12 hours of the day than you will being paid 9.9p on the ‘buy-back’ rate.’*   

*2026 figures – please check www.electricity.gg/tariffs for latest prices.

A battery will cost more upfront, but it can also make your solar system work harder for you. Ask your installer what it would cost to install a battery, and how long it could take to recover that investment through savings. Please note those saving calculations should factor in paying for your quarterly standing charge too. 

Sometimes people are sold batteries that are too large for their property, which increases payback periods as the battery hasn’t been matched to your roof’s realistic generation limits - or your consumption habits.

The best option is to:

1. Find out how much electricity your property actually uses
2. Install solar panels to power that usage in real-time plus an extra buffer for future installations
3. Save any excess electricity into a properly-sized battery system to use later

If you’re on the Super Economy 12 electricity tariff, you’ve got 12 hours of higher ‘normal rate’ electricity, and 12 hours of ‘low rate’ electricity, which is over 50% cheaper (10 hours overnight and two in the afternoon).

Ask your installer: Based on my property’s consumption, is this battery sized to cover my actual usage when my solar panels are unable to supply the power directly?

5. Will Guernsey Electricity buy my excess solar power?

Not necessarily. It very much depends how much power your neighbours and the people living close by need (demand) at the time your solar panels are generating extra electricity over and above your needs (supply).

Because energy can’t be created or destroyed, any unused solar power builds up, raises the voltage, then forces your panels to switch off temporarily.

Check with your installer what to do if this happens, and whether the system will automatically restart.

We’ve seen cases where systems switch off for safety reasons but don’t come back on automatically, meaning customers think they’re generating solar power when they’re not.

As your solar panels will work overtime on very sunny days, they'll produces far more power supply than your home actually needs/demands. And all the solar panels around you are doing exactly the same.

The catch? The grid can’t take all that extra energy – because nobody needs it.

When voltage gets too high, your inverter will shut off the solar system to prevent damage. Sometimes these systems are then unable to switch themselves back on again automatically when clouds cover the sun and voltage drops, which is why some people find their solar systems switch off on very sunny days.  

If you use a water butt to collect free rainwater, you’ll know that once it’s full, it’s full. The same goes for solar. We physically can’t push any more energy into a system people are not currently using.   

Ask your installer: Does your payback calculation assume I will export every single spare unit of electricity, or is it safer to treat the non-guaranteed buy-back revenue as a helpful bonus only?

6. What is a ‘Buy-Back’ rate?

This is a fixed amount of money Guernsey Electricity may pay you for the units of surplus power your solar panels generate and feed back into the island’s electricity grid.

It’s cheaper per unit for Guernsey to import clean energy from Europe or generate it locally at the power station than to pay individuals a buy-back rate for their surplus solar during sunny summer days.

This is because supply is high but demand is low. Electricity imported from Europe is bought on a live market, where prices rise and fall depending on supply and demand, much like a stock market. By contrast, the solar buy-back rate is fixed, so the price doesn’t fall when lots of solar is being generated on-island.

As Guernsey Electricity are legally mandated to supply the cheapest possible electricity, paying artificially high buy-back rates to solar panel owners would mean thousands of local islanders who don’t have solar panels would need to subsidise those who do through higher electricity bills.

The best approach is to:

1. Understand how much electricity your home uses
2. Size your system to match it (with a small buffer for future needs), and, if possible;
3. Install a correctly sized battery so you can store and use more of your own solar power.

Your installer will also need to send an ‘EE40’ private generation form to Guernsey Electricity to register for your buy-back. This simply lets us know your system is exporting power, so we can record it properly and pay you for what you do send back.

Ask your installer:  Will you provide me with a copy of the approved EE40 connection confirmation from Guernsey Electricity before installation begins to make sure I can receive buy-back payments where possible?

7. How will Guernsey’s weather affect my yields?

Solar panel brochures rarely get excited about grey January days in the Channel Islands. Like much of Britain, Guernsey sees plenty of cloud and shorter winter days, which means when we're all using the most electricity, solar generation is likely to be low. The maritime climate here means local weather patterns can create a direct mismatch between supply and demand.

• Winter: A typical 4 kilowatt (kW) solar array might happily pump out plenty of electricity on a clear sunny day during a surprise heatwave in May. That same day might see hundreds of islanders’ flock to Herm, Sark, or head to their favourite beach with the family. With few people home, your fridge and perhaps a few electronics left on standby enjoy your free solar power. On the flipside, when you absolutely need the most power – usually around 6pm on a cold January evening – rounding errors may show that exact same solar system producing closer to 0 kWh. Lack of winter sun forces you to switch on more lights and plug in some heaters, meaning you’re entirely reliant on the electricity grid exactly when the solar falls short.
• Summer: Guernsey Electricity manage the power network using hundreds of local substations scattered across the island. These manage the power grid based strictly on the immediate demand of that specific local area. Imagine that record high heatwave in June – many people are outside catching some rays themselves. This is when the nearby solar panels will suddenly try to pump hundreds of units of excess power back into the local grid at exactly the same time. But with no local demand to absorb it, your system voltage spikes. To protect it, the solar inverter will automatically kick in and shut off your panels. 

 Ask your installer: On a sunny day when a high-voltage spike in my PV system forces my panels to turn off, how do I safely reset it if needed so I don’t lose out on any solar generation when the voltage drops again?

8. Will I still need to pay a standing charge if I’ve got solar panels?

Yes.

Standing charges help cover the ‘fixed costs’ of running an electricity network, which here in Guernsey includes (but isn’t limited to) the subsea importation cable, power generators and the local underground cable network. These need to be maintained and kept ready 24/7, so electricity is always available when you need it, regardless of how much you use day to day.

These types of charges are common across energy suppliers in all jurisdictions.  

• ‘Fixed costs’ – this is what your standing charge pays for. It covers the multi-million-pound cost of running a grid, including over 1500km of underground cabling and around 500 local substations supplying power to people on the coldest, darkest day.
• ‘Variable costs’ – this is the electricity you physically use, and solar panels should considerably lower this part of your bill.

Even if you use very little electricity, your home still needs to stay connected to the grid, which is ready to supply power whenever you need it. Standing charges help energy suppliers cover that ongoing cost, which is why everyone contributes.

Ask your installer: Does my payback period calculation factor in my quarterly standing charge, which will remain in place even after my solar installation?

9. What is my payback period for a solar installation?

First, check the back of your most recent electricity bill to see which tariff you’re currently on. Your installer needs to give you a quote based on the exact tariff you’re using, and not only rely on the highest tariff price.

The image below shows the back of an electricity statement for a customer who users a Super Economy 12 tariff for their lighting and power. If you would like to know how much you've used during your 'normal' rate and 'low-rate' times over the last year, you can either check the last year’s bill or give our customer service team a call.

Super Economy 12

• Low Rate: This runs for 12-hours and is split into 10-hours overnight and 2-hours in the afternoon at a rate around 50% cheaper than the higher ‘normal’ rate (see below)
• Normal Rate: Covers the remaining 12-hours of the day and is more expensive to use

Standard Tariff

This is a flat rate charged at the same price 24/7 and is around 50% more expensive than the Super Economy 12 low rate.

To get the fastest return on your investment, the best advice is to shift your heavy electrical usage away from peak times. If you can, use your solar power during your ‘normal’ high-rate times or use a battery to cover those peaks.

Keep in mind that solar panels can’t offset electric heating in Guernsey when it’s measured on a separate meter. This means if you use electric heating, your payback calculation should be based only on your light and power usage, such as appliances, lighting and sockets, and not your total household electricity use.

Ask your installer: Can you give me an approximate payback period based on the specific electricity tariffs my property uses for lighting and power?  

10. Do I need planning permission to install solar panels?

For roof-mounted solar, planning permission on existing homes is usually not needed, provided your panels meet specific exemption criteria set out by the States of Guernsey. Rules may differ if you live in Conservation Areas, a protected building, or the airport safety zone.

However, your installer will need to send an ‘EE40’ private generation form to Guernsey Electricity.

Regardless of planning exemptions, you must register your solar panels with Guernsey Electricity to get formal permission to connect to the electricity grid. Without approval, it’s impossible to legally connect your ‘self-generation’ system, meaning you can’t receive any buy-back payments for excess power.

Ask your installer: Will your team handle the entire EE40 application process with Guernsey Electricity on my behalf and will you provide me with formal grid connection approval documentation before the installation begins?

11. What will happen if a solar panel breaks?

If a panel breaks or stops working, often you’re protected by product and performance warranties. Your micro-inverter or string monitoring system should flag a drop in power immediately on a mobile app, and your first point of contact will be your original installer.

Guernsey Electricity sometimes receive calls about faulty solar panels, but if the issue relates to the equipment itself, it isn’t something an electricity provider can fix. The best thing to do is contact your original installer.

Some product warranties will cover the cost of the hardware, but not necessarily the labour to climb on your roof and replace the panels, so it’s best to check this with your installer ahead of installation too. Also check if the warranty pays for scaffolding to access your system. If it doesn’t, please make sure to factor this into your purchase calculations, as scaffolding in Guernsey can be expensive.

Ask your installer: Does the warranty cover both the hardware failure plus the diagnostic labour and roof-work cost including scaffolding, or will I need to pay a fee to have any damaged panels replaced?

Bonus question – can I go off grid?

The dream for many is to be entirely self-reliant by generating their own power. With today’s technology, it’s certainly possible, and depends on how much electricity your property uses.

Check your electricity bill after you’ve had your self-generation system installed for a full year.

If your variable charge is consistently £0 and you’re only paying a standing charge, then this would suggest your solar panel system is able to cover all your needs and you never need to rely on the grid as a back-up. But before going off grid, make sure to have a Plan B in case your solar system stops working.

If there is a ‘variable charge’ on your bill, this shows your property is still drawing power from the grid, and your standing charge is helping pay to get that power sent to your property.

See how that power gets to you 

Who installs solar panels in Guernsey? Click to find an installer

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12 Questions to ask your solar panel installers