Two NCS members describe how they selected a domestic Solar System for their new home that was then installed in March 2020. 

Some pointers and lessons learned

• Despite the end of the Feed-in Tariff and the low export rates available with the Smart Export Guarantee, we still estimate an annual return on investment of 3% (5% if you exclude the optional EV charger and Tesla battery) – well above current cash savings rates.
• The latest systems now function on East- and West-facing roofs and a South-facing roof is not a critical requirement.
• New monocrystalline panels are expensive but they are more efficient and many people find them more aesthetically pleasing.
• UK Power Networks has to approve your proposal for micro generation and often limits how much you can export to the grid.

Background

Having purchased a new home in Norfolk in late 2019 with a large South-facing roof plus East- and West-facing pitches, we looked into buying solar PV. We invited two local companies to survey the property and provide quotes. Having moved from a small mid-terrace in Norwich with low energy requirements to a larger detached property near the coast, we had no data on our annual energy consumption. Our request was to maximise the use of our roof space, generate as much as possible and to include the option of heating the existing Heatrae Sadia hot water tank by bypassing the gas boiler. We needed enough power to charge our Nissan Leaf EV as well. 

Initial research and quotes

We discovered that the technology had advanced since we last looked at options in 2013. At that time, we were informed that having an East-West facing roof would minimise the efficiency of PV panels. Any shade on one panel would reduce the power generated from all. 

In January 2020, we found out about new inverter technology which makes it possible to have PV panels on East- and West- as well as South-facing roof spaces to maximise the power produced. The shady panels are switched off while those in the light carry on generating at maximum output. So, each panel produces the maximum energy and power losses are eliminated.  

We were told that the colder sunnier days we get on the East coast are more productive than in hotter temperatures enjoyed in the South of England. PV panels are, ironically, less productive in very hot climates. We knew that the Feed-In-Tariff (FiT) was no longer an option but were not aware that micro-generators still get paid for any excess exported to the grid thanks to the Smart Export Guarantee (SEG). Then we discovered that, although the SEG became law in January 2020, only the big energy providers are being forced to pay for exported energy. We were using Good Energy (the original campaigners for FiT back in the day), and they had not got around to complying to the SEG. Changing providers during the pandemic has meant that we cannot get a smart meter installed and our excess is going back into the grid for no return. On the other hand, working from home during the pandemic means we are using a lot more of our solar electricity during the day than we would otherwise. 

It took nearly two months to get a quote from one company (indicating that they were too busy to prioritise our small project) and a single day to get an initial quote from the second; suggesting that they were keen! We used their recommended system and initial quote to inform further research. We looked at alternative manufacturers, more powerful panels, differing warranty periods and reviews. We realised that the initial quote was based on the assumption that we wanted to install panels as a financial investment rather than prioritising environmental returns. 

The initial quote was for a 7.5KWp system using 25 x JA Solar panels which were polycrystalline. We finally opted for a 9.75 KWp system (to maximise winter generation) using 25 x Sunpower 390 panels which were monocrystalline. We researched the differences between monocrystalline and polycrystalline panels. Monocrystalline panels are expensive, but they are aesthetically more pleasing (an opinion) and more efficient (a fact). Sunpower 390 panels also came with a longer extended warranty than the JA Solar panels. There are many reviews on the internet that can be found with a quick search on Ecosia or Google. This is a quote from one: “Monocrystalline panels have a long lifespan. Most solar panel manufacturers put a 25-year warranty on their monocrystalline solar panels. Because both types of crystalline solar panels are made from crystalline silicon, a stable material, it is very likely that these solar panels will last much longer than their 25-year warranty life.”  

We had lengthy discussions with our installer (who has been in the business since 2008) before making the final decision. We consulted our neighbours who suggested that the large wood pigeon population would necessitate the installation of bird guards. 

We also decided to install an EV charger for our Nissan Leaf, factoring in a government grant of £500. It is vital to use an installer approved by the UK Government OLEV (Office for Low Emission Vehicles) scheme to obtain this grant. 

Installation

We opted for the following package:  

• 9.75KWp system using 25 x Sunpower 390 panels
• Tesla Powerwall 13.5KWp battery for storage of unused energy  
• SolarEdge SE10K inverter
• I boost power diverter (for the hot water tank)
• EO smart home EV charger 
• Bird guards 

Early data March 23rd – June 5th 2020

System commissioned: 23/3/2020

Today’s date: 5/6/2020

System production to date:           2.8 MWh

CO2 Emission Saved to date:       714.99 kg

Dark cold rainy day 5/06/2020: 27.38kWh

Full sunshiny day 31/05/2020       63.44 kWh 

Comparative data illustrating spring 2020 weather variances: 

31/03/2020:                                      45.27 kWh

25/04/2020:                                      39.62kWh

30/04/2020:                                      18.16 kWh

Estimated financial and CO2 savings: (yet to be verified – we think it may be better than this) 

Size of PV System: 9.75 kWp

Annual Generation: kWh CO2 Emissions Avoided: 3,111.5136 kg (actual to date is 714.99 kg for 71 days)

Export = £ 0.0500 per kWh

Money saved by Diverter (avoiding gas water heating) = £150

Money earned from Export 20% of income = £144

Electricity bill savings 59% of income = £431

Total Year 1 benefit = £724

Investment for installed system = £14,700 (£23,600 with the EV charger and Tesla storage)

ANNUAL TOTAL RETURN ON INVESTMENT = 3% on complete system (5% excluding EV charger and Tesla storage).

Installer: Green Home Energy Solutions based in Upton, Norfolk – Excellent customer service, fuss-free installation. 

Other things you need to know

UK Power Networks has to approve your proposal for micro generation and often limits how much you can export to the grid (unless you pay for a network upgrade in your area – I was told this was quite expensive but cannot find out exactly how much) We were limited to 3.68 kWh – but in the height of summer on sunny days we are exporting up to 30 kWh per day after filling the Tesla Powerwall.

Going forward

On Nigel Hargreave’s advice, we looked into V2G (Vehicle to Grid). But found that our system was considered too large to be put forward for trials with Ovo Energy. They were collaborating with Nissan Leaf (our car model).  

We will keep an eye on all the different trials going on where energy providers pay the customer to import or export electricity to or from your battery during peaks and troughs in the supply. See footnote 2 on “demand side response (DSR)”. 

What is needed now is a concerted programme from UK Power Networks and the other regional electricity distributors to update the grid to accept more microgeneration and therefore reduce the national reliance on fossil fuels or nuclear energy.

The Tesla and the SolarEdge apps make for compulsive viewing – we enjoy looking at how much we are producing, consuming, storing and exporting at any one time! 

We are also keeping an eye on how domestic wind power technology develops to cover the drop in PV energy production during the winter months when the days are shorter. To date, we have not found any wind turbines that are suitable for domestic microgeneration. They need consistent wind power and direction.  

Footnotes