What’s the difference between the two different types of solar energy systems?
Solar panels heat water using the warmth of the sun and transfer that heat to your domestic hot water system.
Photovoltaic (PV) systems are ‘solar cells’ that use sunlight to generate electricity for use in the home. Any excess electricity can be sold to the National Grid.
Is my home suitable for solar energy?
The basic minimum requirements for both solar water heating and PV systems are much the same:
- unobstructed exposure to the sun during the sunniest part of the day, typically between 9am and 3pm
- an opportunity to mount the panels or cells at an angle between 20 and 50 degrees to get the most benefit.
A south-facing roof that enjoys direct sunlight during the two hours either side of noon is particularly ideal.
How much available roof space will it take up?
You’ll typically need to allow:
- about four square metres for solar water heating panels
- 12 to 16 square metres for a PV system.
How much does it dost?
Costs for the average home are:
- £3,000 to £5,000 for a solar water heating system
- £4,000 to £9,000 or more for a PV system.
How much energy will it save?
- solar panels should save around one-third of the energy used for heating water
- PV will generate around 750–800 kW hours of electricity annually.
Will I need lots of batteries?
You do not need batteries for solar water heating.
If you’re planning a PV installation that isn’t going to be connected to the National Grid, you’ll need to use batteries to store the power generated. Your installer or supplier should be able to advise you on the right sort for your system, as well as the necessary additional equipment you’ll need to regulate their charging.
Do I need planning permission?
Since April 2008, the need for planning permission has been removed from most micro-generation technologies in England, allowing them to be installed under the General Permitted Development provisions.
But there are still some occasions when planning permission will still be
needed, eg if the panels:
- will protrude more than 20cm
- are in a conservation area and visible from the road.
It’s always best to check with your local council before doing anything, although there shouldn’t be a problem for most householders.
In Scotland, Wales and Northern Ireland, planning is a devolved issue; although similar legislation is coming into force, it is essential to check with the appropriate authority to stay on the right side of the relevant country’s law. You can find out more from your country’s planning portal using the link below:
What happens when it’s cloudy?
Obviously both PV and solar water heating work best when the sun shines, but even on cloudy days, all is not lost. When the sun does peep out from behind the clouds, there can often be enough heat to help warm the water, but there’s no escaping the fact that this sort of solar energy system really needs the sun’s warmth to make a serious contribution to household energy savings.
Modern PV systems run surprisingly well even under overcast skies and will continue to generate at least some electricity at quite low light levels – but as always, the sunnier the day, the better!
Many people installing solar systems also choose to invest in other renewable technologies to make up for times when the sun doesn’t shine; wind power or wood-burning stoves, for instance, can be used to make up the shortfall.
Is it worth it?
That depends on how you view things.
Neither system has a particularly fast payback, so unless you’re planning to stay in your current home for several years, it’s probably not worth it from a purely economic standpoint.
But for community buildings the long-term answer has to be yes, for obvious reasons.
However, where this kind of approach really comes into its own is in terms of reducing your carbon footprint: a typical domestic PV installation will save around 1 tonne of carbon dioxide emissions annually. According to World Energy Council figures, electricity from PV costs between 0.01 and 0.1 kg of carbon dioxide per single kWh, five times lower than electricity from a gas-fired power station and at least 10 times lower than a coal-powered one.
Saving energy isn’t all about lower bills, although it’s certainly nice when it does!