Frequently asked questions
Is there really enough sunlight in the UK for it to work?
Yes. The UK receives slightly more than half of the solar energy received at the equator, ample to operate a solar water heating system. A typical solar water heating system in the UK provides 50% - 70% of annual domestic hot water requirements. This is spread out over the year to approximately 90% in summer, 50% in spring, and 20% in winter. A solar system provides heat input even on cloudy days by utilising energy from diffuse light. In winter the system will pre-heat the water in your cylinder, meaning the solar system will make meaningful reductions to your gas, oil or electricity consumption throughout the year.
How do I get hot water when it isn’t sunny?
The solar water heating system works alongside your existing hot water system. On cloudy days, the little sunlight there is will preheat the water in your cylinder – and your boiler or immersion heater will do the rest.
How big is the panel?
This depends on the optimal size of system for your property, number of people in the house, capacity of cylinder installed, and available roof area. Generally a 2-person household would have a 2.75m2 panel and a 3-4 person house a 3–4m2 panel. The installer will advise on the best sizing for your property during the site visit.
Who fits the solar water heating systems?
Heating engineers who have been specially trained in installing solar water heating systems have been selected as Solar for London installers through a competitive tender process.
What will need to be done?
If the solar panels are to be installed on the roof, scaffolding will need to be erected to comply with Health & Safety requirements. The installers will also need access to the loft space. Your existing cylinder will need to be replaced by a dual coil cylinder. The panel will be connected via new pipe work to the dual coil cylinder. Securing the panel involves removing and replacing half a dozen roof slates/tiles.
How long will it take to fit?
A solar water heating system can be fitted in about 2 days by professional installers with a minimum of disruption and mess. Installers will clean up after themselves. You should not be without hot water for more than a few hours.
Can it be fitted in any direction, on any roof?
The solar panels need to face in a southerly direction (ideally somewhere between southeast and southwest), and ideally they should be fitted on a sloping roof.
Can it be fitted onto a flat roof or onto a gable end?
Yes to both, but the panel would need to be mounted onto a special frame and extra piping may be needed. There would be an additional cost, which the installer will discuss with you.
Will I be able to fit a solar system in a loft conversion?
In some cases it is possible to incorporate solar with a loft conversion, however for many it is impractical. You have to imagine how the pipes will connect from the back of the collector to the hot water cylinder. You should ask yourself, will the pipes come out into the room and is there access to connect pipes to the hot water cylinder?
Is a solar water heating system compatible with a combination boiler?
Most combination boilers (combi) are designed to take in cold, not preheated water and are thus not compatible with a solar water heating system. There are a few combi’s on the market that will accept pre-heated water and you should check with the manufacturer whether this is the case if you have a combi, or are installing a new one and wish to have solar as well. It is advisable to get the manufacturer of the combination boiler to state in writing that the combi boiler in question will accept pre-heated water.
Alternatively your combi boiler can be altered so that it functions as a standard boiler connected to a dual coil cylinder however this will void manufacturers guarantees and is not generally recommended.
Another option available through Solar for London is the Solar-combi system.
The solar combi system is a unique solution allowing solar to contribute in situations where an intermittent requirement for very large quantities of hot water would favour the use of a combi or multi-point.
A potential difficulty with any stored hot water system is that at times of very high hot water demand, the cylinder might not have sufficient time to build up a store of hot water (even a high recovery coil is unlikely to deliver more than 9 kW). This can lead to water below the required temperature being delivered to the taps. In situations where this could occur, simply installing a very large hot water cylinder to cover these brief periods of high demand may be inefficient or simply impractical; a combi or multi-point would therefore be the preferred solution. Although this would normally preclude solar, there is now a system available through Solar for London that allows the solar heated water stored in a standard size cylinder to be used first, providing the energy savings. When the solar heated water that is stored in the cylinder has been used, the combi takes over, efficiently providing the required hot water.
What savings should I expect?
Financial savings will depend on the amount of hot water used, your boiler efficiency, and the type of fuel used to heat your water normally; (gas tends to be cheaper than electricity). Savings could therefore be £20 - £120 per year. By installing a solar system you will also be helping to protect the environment by reducing emissions of carbon dioxide, (CO2 the main greenhouse gas) at an average of 440kgs per year.
Will I need Planning Permission?
You can make certain minor changes to your home without needing to apply for planning permission. These are called ''permitted development rights''. Installing a solar panel comes into this category. However permitted development rights do not apply if you live in a listed building or in or near a Conservation Area, a National Park, or an Area of Outstanding Natural Beauty. In these cases planning permission for fitting a solar panel onto your home should be applied for.
Local authorities can withdraw permitted development rights. We recommend that you check with your local authority planning department whether you need to apply for planning permission. Ring your local authority and ask to speak to the duty planner.
Does a system need much maintenance?
No. There is very little that can go wrong with a solar system – they require much less in the way of maintenance than any conventional boiler – and their lifespan of over twenty years is more than double the lifespan of a normal boiler. The installer will leave written details with you after a system is fitted and commissioned, detailing the simple maintenance checks that you can undertake from time to time to see if everything is working properly.
Will the water ever get too hot, is there a risk of scalding?
No. The systems are all fitted with a thermostatic mixing valve as standard so the temperature of water coming out of your hot taps is therefore set as standard. The systems are also designed so that overheating does not occur.
Are there any guarantees or warrantees?
Panels come with either a 5 or a 10-year guarantee. Other components and all labour are warranted for 1 year.
What situations might mean that there would be extra costs?
- If panels have to be fitted to walls (e.g. a south facing gable end) or on a flat roof.
- Scaffolding required – cost varies depending on whether a tower can be used or bespoke scaffolding needs to be erected.
- If you have a loft conversion or an attic room.
- If an unusual amount of additional pipe work is needed (more than 20 meters).
