Alconbury Road, London E5
2 roofs L shape, 16 Modules 4kWp system with Micro-Inverters.

The main roof and back extension of this Victorian terrace accommodate a 4kWp solar PV system, which is the maximum size permitted to qualify from the higher rate payments under the Feed-in-Tariff scheme.

16 Panasonic Hybrid solar panels producing up to 240W each are spread over the two roofs to minimise shading from typical obstacles like chimneys. To maximize the output this system uses Micro-Inverters, which offers further advantages:

With 6 panels facing south-west and 10 panels facing south-east, this generator has produced 2000kWh in the first seven months.

To make the most of the free solar electricity an ‘Optimmersion’ (Energeno) was installed. This device detects and re-routes any surplus solar energy to the Immersion heater to keep the hot water tank at the chosen temperature and so reducing the need of the boiler heating up the water. On 27th September David e-mailed us to say “The gas charge is down to £8 per month, I think because the hot water is all from the solar”.

This very happy customer also installed a CHP boiler (Central Heating and Power), gaining even more in-house generated electricity. This boiler is 100% efficient through its ability to convert surplus heat into electricity, earning 10p per KWhour under the CHP FiT scheme.

System Cost: £10,500 

Estimated energy output: 3080kWh 

Expected Feed in Tariff p/a: £475 (at p15.44 rate) 

Total annual income and bill savings: £787 

Annual return on investment: 7.8%
Payback period: 9.5 years

Paradise Row, Stoke Newington
Although only a small roof space we managed to
install a configuration of 10 Solar PV panels that produce a good income for this N16 landlord. In a competitive rental marketplace, our customer is also able to offer reduced electricity bills as an added incentive to her tenants.

System cost: £9000
Electricity savings pa: £117
Total income pa: £ 887
Payback time: 10 years
Lifetime benefit: £22,180

Bouverie Rd, N16
It’s a small valley gutter roof, allowing only for 8 solar panels on the south-facing side to be installed. That’s why the customer went for the powerful 250Watt Hybrid panels, which are adding up the electricity production to a staggering 2kWpeak system (2000Watt peak at any given moment during a sunny midday in July). The system is expected to produce around 1820kWh (that is 50% of the yearly use of an average household).

System size: 2kWp
System cost: £10,000
Electricity savings pa: £114
Total income pa: £ 930
Payback time: 11 years
Lifetime benefit: £23,500 (tax free and index linked)

Cecil Road

14 Sharp NU 185W modules making a 2.6kWp system
Annual expected output: 2300kWh
Yearly FiT payments: £995 plus bill savings of £145
Lifetime benefit: £23,975.00
Total cost (incl VAT): £11,336.85
Payback time: 9.8 years
Annual return on investment: 10.2%

Hawksley Road London N16, East – West System 3.92kWp, 2 x 8 Suntech 245W modules

By utilizing the East and West facing slopes of this 3-storey mid-terrace property, the available mounting area was doubled and we were able to install the maximum eligible system size (<4kW) to benefit from the higher FiT tariff. This installation has two solar arrays: 8 modules facing east, catching the morning to midday sun and 8 modules to the west converting the afternoon and evening sun into electricity. Compared with a south-facing array, east-west solar systems work longer hours and so make up for the minimal losses (around 15%) of not facing south at the optimal angle. The electricity output will cover around two thirds of the annual electricity needs for this property and its inhabitants and guarantees an enormous bill reduction apart from the FiT and export payments for 25 years.

System Cost: £10,400
Estimated energy output: 2750kWh
Expected Feed in Tariff: £577 (at 21p rate)
Total annual income and bill savings: £797
Annual return on investment: 7.7%

190 Evering Road, London E5, 3 in 1: Multi Green-Roof with Top-Up from the west slope

This large hipped roof already had a Solar Thermal system installed on the south-facing roof as well as a velux window, leaving limited space or a pv system. By using the highly efficient Panasonic Hybrid 240 Watt panels, we were able to install a ‘staggered’ array of 5 Modules 1.2kWp system producing up to 1050kWh per year. To top this up, a second array of 5 Hybrid Modules were fitted on the west-facing slope of the roof to catch the afternoon and evening sun and add around 700 to 800kWh p/a to the total of this PV system.

System Cost: £9,500
Estimated energy output: 1942kWh
Expected Feed in Tariff: £841 (at 43.3p rate)
Total annual income and bill savings: £992
Annual return on investment: 10.5%

Evering Road E5, 2.9kWp system, 12 Sanyo Hybrid 240W modules

An end of terrace Victorian house with its typical hipped roof shape allowing for 12 modules to form a 2.8kW system, producing around 2400kWh per year and replace up to 40% of the annual energy imported from the grid. Being located in a Conservation Area, the Homeowner obtained a ‘Certificate of lawfulness’ from the local planning authorities for this project. Since October 2011 planning restrictions for the installation of solar panels have been relaxed and planning permission is not normally required for the installation of roof mounted solar panels in a Conservation Area.

System Cost: £13,000
Estimated energy output: 2370kWh
Expected Feed in Tariff: £1040 (at 43.3p rate)
Total annual income and bill savings: £1230
Annual return on investment: 9.5%

Highbury New Park, London N1 - Case Study

Coping with shading - chimney stacks on London Roofs.

On most London roofs there are chimneys in various shapes and forms towering above the ridge heights and casting shade on to the solar panels at certain times of the day and as the sun changes its path during the seasons.

This property’s roof is south-facing and has a large chimney stack to the west, which will affect parts of the array from around 3.30 in the afternoon and lower the output as soon as one of the panels gets shaded. The solution here was to split the array into 2 independent strings, one string connecting all the panels that will be affected by the afternoon shade and the other string connecting the unaffected modules, which are furthest away from the chimney walls and can receive more hours of unobstructed direct sun light.

System Cost: £10,400
Estimated energy output: 2318kWh
Expected Feed in Tariff: £841 (at 43.3p rate)
Total annual income and bill savings: £1207
Annual return on investment: 11.6%

Carysfort Rd N16 - Case study lead flashing, Slate roofs – lead flashing for solar panel mounting hooks

Fitting solar PV systems on to slate roofs requires special skills as the steel hooks carrying the mounting system need to be fitted securely to the rafters without leaving the roof prone to leaks where the hooks protrude through the slates. Our experienced roofers are using lead flashing which hugs neatly around the hooks and the surrounding slate tiles are then cut to shape to work perfectly together with the lead flashing.

Mapledene Road, London E8 Case Study, Loft conversion with Solar Slates roof-integrated

As part of loft conversion works at this small 2 bed Victorian terrace house, the solar system has been integrated into the roof and blends beautifully with the new natural slates fitting exactly between the two Velux windows. Two rows of 47W solar slates form a 1.13kWp system should return up to 1000kWh per year, reducing electricity imported from the grid by around 35%.

System Cost: £6,950
Estimated energy output: 961kWh
Expected Feed in Tariff: £416 (at 43.3p rate)
Total annual income and bill savings: £496
Annual return on investment: 7%