Where it’s possible, an investment in rooftop solar can help you reduce your electricity costs long into the future and increase the value of your home. Having less-expensive solar power can also increase the cost effectiveness of other green technologies, like EVs and heat pumps, compounding your ability to cut your carbon footprint.
£6,000 - £8,000
Based on typical system size of 4 kW
About the technology
How it Works: A rooftop photovoltaic (PV) system uses solar panels to convert sunlight to direct-current (DC) electricity. An inverter then converts from DC to alternating-current (AC) electricity – the type used in your home.
Grid-Tied Systems: Most rooftop PV systems are tied to the electrical grid. This allows you to take electricity from the grid when you need extra (such as at night) and put electricity onto the grid when you generate more than you need. Generally, your local utility will provide a credit for the power you put on the grid.
Battery Storage: Battery systems can be installed along with solar as a backup power source during power outages. Also, depending on your electric rates, a battery can store cheaper solar power for later use to reduce the need for high-priced electricity from the grid. Given the high cost of battery storage, however, this storage of power for later use is generally not cost effective.
Economics: How much you’ll save by going solar depends on a variety of factors specific to your situation. For many, however, solar is now a cost-effective option, with systems paying back in less than 8 – 10 years — well under a system’s expected life of 25 years.
Environment: The environmental benefits of solar largely depend on the level of emissions associated with the grid-supplied power being displaced. The benefits are greatest where fossil fuels (such as coal, oil, and natural gas) provide a large percentage of the local power.
Maintenance: Very little routine maintenance is required. Rinsing or washing the solar panels a few times a year will remove dust/debris that can degrade the system’s efficiency. With the exception of certain types of inverters (which may require replacement after about 15 years), the components can be expected to last for the lifetime of the system.
Frequently Asked Questions (FAQ)
1. How does a solar system work?
A solar electric system, also known as a photovoltaic (PV) system, uses solar panels to convert sunlight to electricity. The panels produce direct-current (DC) electricity, which must then be converted to alternating-current (AC) power — the type used in your home. An inverter (or a series of panel-mounted microinverters) is used to convert from DC to AC power. Almost all solar systems are “grid-tied”. When you produce more electricity than you use at any given time, you put that electricity back onto the power grid and generally obtain a credit for the power you provide.
2. How can I tell if my house is a good fit for solar?
A home with an uncluttered south-facing roof and little or no shade is ideal. Somewhat shaded roofs and east- and west-facing roofs also are viable, but have a lower annual output for the same size solar system. A qualified solar installer can perform an analysis of your roof and suggest your best options.
3. Does having solar on my roof mean I am “off the grid” and not connected to my local power company?
No. Having solar on your roof does not generally mean you are “off the grid”. The great majority of solar systems are “grid-tied” systems, allowing a homeowner to use the electrical grid when needed. For example, you can often put excess electricity onto the grid during the day when the sun’s shining and draw power back from the grid at night.
Battery backup systems can be installed along with solar as a way for homeowners to deal with temporary power outages. Although it adds to the cost of the system, batteries can provide power to critical appliances such as refrigerators and computers. Battery systems can even be sized large enough to power all of a house’s electrical loads for multiple days, but that’s generally cost prohibitive for the great majority of homeowners.
4. Do solar systems work in a power outage?
In general, if your grid-connected solar system doesn’t have battery storage, your system will shut off in the event of an outage. This is to prevent emergency responders and electric utility personnel from being injured by electricity that is being fed back into the grid from solar systems.
5. What happens at night or on cloudy days? Where does my electricity come from?
At night and on very cloudy days, a solar system goes dormant. During these times you will get power from the grid.
6. Will my roof leak?
Solar mounting systems rely on the same leak-resistant technologies and installation principles as other roof features such as vents and exhaust fans. Ask your solar installer how your system will be mounted and how any roof penetrations will be sealed.
7. Does my roofing material impact my ability to get solar?
The solar industry has created mounting methods and equipment for most of the commonly used roofing materials. Some materials (such as composite shingles or metal standing seam) are generally easier to install solar on, and others (such as clay tiles) present more of a challenge and may involve a higher installation cost.
8. What happens to the solar hardware when I sell my home?
Because they are designed for a specific location, solar systems almost always stay with the home on which they are initially installed. The cost to remove and reinstall a system on a different home is very high. Solar homes typically have a higher resale value because they have lower monthly energy costs.
9. Can I heat my pool with my solar electric system?
An electrically driven heat pump (powered by solar electricity) can be used for pool heating, but another solar technology normally used to heat a pool is called solar thermal heating. This warms the water directly in solar thermal panels facing the sun. This approach is different from solar photovoltaic technology which generates electricity.
10. Can I provide hot water (for showers, etc.) with my solar electric panels?
Two key solar technologies are available for providing hot water for a home. Solar thermal (not solar photovoltaic) heating involves running a fluid through a particular type of solar thermal panel. This is a more-direct way to use solar for water heating, but is generally expensive and prone to leakage and other maintenance problems. The other approach involves producing electricity in solar electric panels and then using this electricity for water heating. You can use a highly efficient heat pump water heater (HPWH) or a conventional electric water heater.
1. How much do solar systems cost?
System costs vary by size and technology. A typical roof-mounted system normally ranges between £1.5 – £2 per Watt. For a 4 kilowatt (4 kW, or 4,000 Watt) solar system, costs generally range between £6,000 and £8,000. Smaller systems generally cost more per Watt than a larger system. In some cases, homeowners going solar don’t pay for the entire system up front. Instead, they take out a loan, or participate in a lease or Power Purchase Agreement (PPA) program. If you can afford it, the economics of the direct-purchase approach are generally the most favorable.
2. What is the Smart Export Guarantee (SEG)?
The SEG is similar to a feed-in tariff in that electricity suppliers will pay you for the excess power that you put onto the electrical grid. This happens when your system is generating more power than you’re using at any particular time. The price you’ll be paid is substantially lower than the price that you pay when taking electricity from the grid. Accordingly, the economics of solar are much better if you can use (during the day) a high percentage of the solar energy that you generate, as opposed to sending it back onto the grid. You’ll need to have a smart electric meter when you go solar so the amount of electricity going onto the grid can be measured.
3. What is my up-front cost? What costs might I face later on related to the solar system?
Costs vary greatly depending on whether you purchase the system, take out a loan, or sign a lease or Power Purchase Agreement (PPA). If you purchase the system, you’ll pay the cost of the system up front and also be responsible for any future maintenance. With a loan, you’ll generally pay little or nothing up front for the system, pay back the loan with a monthly payment, and be responsible for any maintenance. With a lease/PPA, you don’t own the system. Typically, you pay little or nothing up front and have no responsibility for maintenance, but you’ll pay a fixed recurring monthly fee for electricity. If you can afford it, the economics of the direct-purchase approach are generally the most favorable.
4. Who benefits most from solar power?
The most cost-effective installations are in homes with larger electric bills, a large fraction of electricity use during the day (when the sun is shining), and unshaded roof space facing generally south. But households without these characteristics can also find the economics of solar to be compelling. Homeowners sometimes install solar as a way to benefit the environment, rather than for pure economic reasons.
5. How does solar impact my property value?
Studies have shown that homes with solar energy systems sell for more than homes without them. However, your property value will likely increase more if you own, rather than use a lease or Power Purchase Agreement with your solar system.
6. Will having a solar system help the sale of my home?
It will depend on how you acquired the solar system and the age of your system. The value of your home is likely to increase if the solar system is free of encumbrances, such as a lease or Power Purchase Agreement (PPA). With a lease/PPA, the details would need to be worked out with your solar provider to transfer the lease obligations to the new homeowner.
7. What is the likely payback period (in years) for my solar investment?
Payback time is determined by many factors, most importantly the up-front cost of your system, the buy-back rate, the size of your average electricity bill, and your electricity-usage patterns. In some cases, households will see a return on their investment within 10 to 15 years, but most will generally have longer payback periods.
8. How long is a typical lease or Power Purchase Agreement contract?
Lease/PPA contract periods can vary, but a 15- or 20-year contract is typical.
9. What happens at the end of my contract if I’m in a lease or Power Purchase Agreement?
At the end of your contract, you’ll need to work with your solar provider to determine if you’ll keep the solar system in your home (there may be a cost associated with this) or have it removed. Your options should be written into your initial contract, and it’s always good to review such contract language carefully before signing an agreement.
10. What if I have a solar lease or Power Purchase Agreement and I want to sell my home? What do I do about the contract?
Typically the contract is sold to the new home buyer, but sometimes there are complications. The options you have in this situation should be outlined in your initial contract with the solar installer, and it’s always good to carefully review such contract language before signing an agreement.
11. After getting solar, what is the fee for removal & replacement of the solar panels if I need to reroof?
If your roof needs to be replaced during the life of your solar system, a professional will need to uninstall and reinstall the part of the system that is on the roof. Before installing solar, you should carefully consider the condition of your roof since the cost for this service can run into a substantial cost.
1. Are solar electric systems reliable?
Yes. Solar systems consist of various components, but the key ones are the solar panels and the inverter(s). While the energy generated by a solar panel degrades a small amount each year, they are generally guaranteed to operate for 25 years. The reliability of an inverter depends on the type. Microinverters are quite reliable and can be expected to last for 25 years. Central inverters, however, are less reliable and can be expected to require replacement before the end of the 25-year expected life of a solar system.
2. How long are solar inverters guaranteed for?
Central inverters (also called string inverters) generally come with a 10- to 12-year warranty, but many manufacturers offer extensions to 20 years for an extra fee. Microinverters generally come with a 25-year warranty.
3. What maintenance do I need to do on my solar panels?
Rinsing or washing the panels a few times a year will help keep the system operating at its best. Washing can be done with a simple garden hose and should be done early in the morning before the panels get hot. There is a very small chance that spraying cold water on hot solar panels can cause damage.
4. Who is responsible for repairs, and what happens if the system breaks down?
This depends on how you choose to install your system. Most lease and Power Purchase Agreement programs include the maintenance costs for the life of the contract. So if there is an issue, you can call your provider. If you directly purchase the equipment or take out a loan for it, you (as the owner) have the responsibility.
5. If a lease or Power Purchase Agreement (PPA) is 20 years long, will the equipment last that long?
Most lease/PPA programs cover maintenance (caused by equipment malfunction) for the life of the agreement. In these cases, the equipment will be maintained at no cost to the homeowner, so you would not be responsible for malfunctions. However, it’s best to check the specifics contained in any agreement.
1. What size solar energy system should I get?
The best size for your solar energy system will depend on a variety of factors, including how much electricity you use on an annual basis, when you use the electricity, the amount of shade that falls on your roof, the electricity price you pay, the feed-in-tariff rate, etc. It’s best to obtain estimates from several solar installers who can perform more-detailed analyses for your situation.
2. If I have an old roof, do I need to replace it before installing solar?
If your roof has less than 15 years of life left, you should seriously consider reroofing prior to installing solar. This is because it can be costly to remove and reinstall the system’s panels and roof mounting hardware if you need to reroof after going solar. A roofer or solar professional can help you determine the amount of life left on your roof. Solar installers can generally coordinate with your roofer if you wish to have solar installed at the same time as you reroof.
3. How long is the install time?
While it can take well over a month or two to plan and contract for a solar installation, an actual solar installation is typically completed within a day or two. Installations need to comply with all applicable regulations.
1. Are incentives available for rooftop solar?
The key incentive available is the Smart Export Guarantee, through which you can be paid for the excess power that you put onto the electrical grid.