Benefits of household rooftop solar – a personal point of view

This blog is the first in an irregular series from the Cornwall Insight team on their experiences of installing or owning various energy assets.

In 2018 I finally acted on the desire to install my own generation at home, largely prompted by the looming closure of the Feed in Tariff (FiT) scheme in March 2019. Although the aim to have a lighter carbon footprint was the main reason, a little number crunching convinced me it would make financial sense too.

The financial case was made easier by participating in a collective purchase scheme, Solar Together Norfolk, run by ichoosr and in conjunction with Norwich City Council.

Anyone thinking of installing PV should seek these collective purchase schemes out as I estimate the total cost of the kit and installation was around 20% lower than if I purchased it directly. The process was smooth and simple (see points 1-6 below), and from the point of entering the collective purchase scheme to generating electricity took about six months.

Collective Purchase Scheme

1.Register for scheme (typically regionally focussed)

2.Scheme operators run auction for installers to bid for work

3.Successful bidders provide a no obligation quote to the householder

4.The householder has some options (e.g. type of panel, size of installation etc.)

5.The installation and kit are under warranty

6.The installer deals directly with the householder to finalise installation details and payment

I opted for the more efficient solar panels, on the basis that the extra cost would be more than offset by the additional generation over the life of the panels. I also selected a control unit that diverts generation to the hot water immersion heater rather than export unused output to the network. Living in a rural, off-gas property the idea of ‘free’ water heating to reduce burning heating oil in my decrepit boiler was appealing. The oil boiler has since been replaced with an electric boiler, but that’s probably for another blog on how I got to that decision.

All in the installation cost around £4,200, significantly lower than the prices I hear being quoted now for similar installations. The set-up is a 4.2kW array on an unobscured south-facing roof, with the diverter for heating water, an inverter (tucked away in the attic) and a gadget to allow generation data to be viewed via an app.

The installation was completed in late January 2019 and took a couple of burly guys less than four hours to install and commission (although the scaffold remained for a few weeks). Being a dyed-in-the-wool energy geek, I tracked half-hourly generation (and real-time output) for the first six months or so, but no longer do.

Generation peaks at around 3.8kW, which is to be expected once the direct current output from the panels is converted into alternating current. Even on the most overcast days in winter, I’ll still get around 200W which is more than enough to power the laptop and have a few lights on.

Annual output has ranged from 4,000kWh to 4,500kWh and results in yearly FiT payments in excess of £250 (a combination of payments made for all units generated, currently 4.21p/kWh, and an export rate of 5.99p/kWh based on “deeming” where the FiT scheme assumes 50% of generation is exported).

Since the installation things have of course changed significantly. With electricity prices being so high, the payback period has obviously reduced. As I’ve only had a smart meter installed in the last few weeks it has not been possible to accurately measure how much of the power generated offsets importing electricity during daylight hours. But even a rough and ready estimate, assuming that 50% is consumed on-site, shows that the panels avoid around £800 a year in electricity bills. I suspect this is an underestimate though as ‘excess’ generation powers the immersion water heater, again offsetting the need for the electric boiler to operate. During the summer months, we can typically survive without putting the hot water on at all and rely on what is diverted to the immersion heater during the day, which remains hot enough for showers the following morning.

An additional and unforeseen benefit has arisen from days now worked at home following the uptake by Cornwall Insight, and many businesses, of hybrid working. Not only does the solar power likely cover all electricity costs associated with working from home, but I also try to ensure appliances are only turned on when the sun is shining.

Finally, the other benefit of solar PV is that, unlike lots of other tech, it doesn’t crash, need updates or have any moving parts requiring regular maintenance. It is probable that the panels will last for a good few decades, so recouping the investment many times over, although the inverter will need replacing at some point in the future as they have an expected life of 10 or so years.

Ed Reed, Head of Learning and Development Services, oversees Cornwall Insight’s online energy markets and net zero transition training service. Our subject matter experts provide up-to-date and role-relevant training for people new to the sector, via our monthly Introduction to GB Energy Markets Academy, and a range of other courses covering low-carbon generation, electricity flexibility services, e-mobility, low-carbon heat, electricity network charging, wholesale markets and risk management, and the future of electricity markets.



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