Solar panels – are they worth it?

Our 5.4kW array soaking up the sunshine

I’m frequently asked whether I’d recommend PV panels, especially since the incentive of the Feed in Tariff (FiT) was lost in spring 2019. So after about sixteen months of living with ours, this seems a good time to offer a summary.

I’ll start by saying that, while I’m no fan of the Government’s appalling record on the environment over the last decade, the FiT has arguable served its purpose – at least when it comes to PV panels (as opposed to, say, wind or hydro). Nine years ago, I had a quote to install a standard-sized array of 4kW for £14,750, all in. Last year we installed 5.4kW for less than £6,000. As the cost of the panels has plummeted, so the twenty-year, index-linked rate at which you’re paid for every kilowatt you generate has dropped – to the point of obsolescence.


I wanted to maximise my available roof space, so incurred extra costs by going over the 4kW standard array size. I also chose to have a nifty wee switch called a power diverter installed alongside my main meter. This senses when I’m generating more energy than needed and automatically turns on the immersion, thereby heating my water with the surplus before exporting what’s left to the grid. Normally this would cost a few hundred pounds, but I opted for a higher-tec version, an ‘eddi’ from myenergi, that communicates with our electric car charger and so optimises the use of our self-generated electricity, all configurable via a smartphone app.

It’s worth investigating the various green loans available, some offering 0% interest and even an element of cashback.


Any PV quote should include an estimate of the likely generation. In my case, the estimate was 4791kWh, though by averaging across the sixteen months we’ve had the panels, I calculate a slightly lower figure of 4622kWh.


It’s possible that the inverter (the all-important box that converts the DC current generated by the panels into the AC current needed) will need to be replaced within the lifetime of the panels – £665 plus straight-swap installation costs.

Beyond that, I’ve wiped down the panels twice in six months. Not necessarily because I needed to, but because I bought a telescopic brush with hose attachment and wanted to play with my new gadget.


My (genuinely green) electricity supplier, Ecotricity, charges 14.36p (+5% VAT) per kWh so, were I using 100% of the power generated, that would be an annual saving of £696.97.

Admittedly, this is where PV works so well for us. Most solar panels owners are out during the day, meaning that once any surplus power has heated their hot water tank, the remainder is exported to the grid (good for the wider public, not so good for individual finances). But I work from home, so can easily choose to run appliances like the washing machine when the sun’s out. We also have two holiday cottages running off the same supply, one of which is entirely electric, and holiday makers are just as likely to be in for lunch as out, and so using daytime power. We also have an electric car that, on the days it’s not out with my wife at work, is very happy to suck up the sunshine. All of which I’m guessing means that our usage runs at over 90%. Or, by the calculations above, an annual saving of more than £627.27.

There’s another saving as well, in the form of the oil I’d otherwise be burning to heat my water. Most days, the oil boiler does still need to top up the tank. And it’s hugely seasonal, with the panels barely touching the water over winter. But it’s a frequent occurrence through the summer months that the boiler clicks on in the late afternoon only to find our 170 litre tank already fully heated. I’ve not done the sums yet to put a price on the oil saving, but it’s a big factor in the appeal of the panels, financially and environmentally.


Then there’s the fact that I managed to squeeze in the registration of the installation only days before the death of the FiT. Whoever dreamt up the scheme never figured on power diverters, and simply assumed that 50% of all power generated would be exported. Consequently I’m guaranteed an index-linked generation rate, and another export rate for 50% of the same. That averages currently at 6.48p per kWh generated = £299.50pa. Over the twenty years of the scheme, even without index-linking, that’s a total of £5,990. And while we have to apportion some of that for income tax given the holiday cottages, for the average homeowner that’s tax free.


My more-expensive-than-average installation cost £5,957.75, but saves us £627.27 in electricity every year, and more still in oil. Even allowing for the cost of a new inverter at some stage, you don’t need to factor in the minimum of £5,990 in FiT payments to see the benefit.

For comparison, a straightforward 4kW installation with power diverter would have cost me around £4,400 and saved me £464pa on electricity alone. Without the FiT, that’s a less than eleven-year payback.

So even after the death of the FiT scheme, PV panels remain a good financial investment.

Of course, this is a general overview. There are other points to consider:

  • Manufacturers reckon on a PV panel’s efficiency decreasing by 0.8% every year, with a 20% reduction in efficiency after 25 years. At the same time, though, grid electricity costs are predicted to rise, and by far more (one recent study suggested an 8% annual increase).
  • When our electric car is home during the day, we use more of our self-generated power than most. But then the chances are, if you install PV panels today, they’ll still be running fine around the time we’ll ALL have electric cars.
  • With the addition of a battery to store the solar power, it’s possible to vastly increase the benefit. (*edit: BUT see this more recent blog suggesting that home batteries are, at the time of writing, little more than a rich (wo)man’s conscience salve)
  • I’m based at a latitude of almost 56º, just outside Edinburgh, Scotland – a country hardly renowned for its year-round blue skies. Yet even here the panels are worth the cost.


All of the above is judging solely from a financial perspective. It says nothing for the CO2 emissions saved by burning less oil, or by the increase in additional renewable power available to the grid once we’ve powered our home, charged our car and heated our water. To me, that’s worth a lot, to the point that, even were it not such a financial no-brainer, I’d be keen to put in panels anyway. I’d go so far as to say that those who can afford to are likely high energy consumers anyway, so have a moral responsibility to consider it.


This is a valid question – as long as the tariff in question is a genuinely green one that increases the overall level of renewables going into the grid, rather than simply claiming a proportion of what’s already there. However:

  • generating your own power on-site gives you a far greater awareness of your consumption and how to optimise it, something we all need to do.
  • since the inverter needs mains power to operate, a power cut makes the panels useless. By adding a battery, though, you can reduce the impact of outages – a depressingly common occurrence here in the country. (*edit: Again, though, see my later post on home batteries.)
  • as electricity prices fluctuate – and more-than-likely increase significantly – your own solar panels will operate as a buffer to mitigate those costs.
  • perhaps most importantly, at present there just isn’t enough renewable energy to run the grid – it needs all the help it can get. In contributing, you’re helping the many who lack the space or the money to install solar panels of their own.


Given that we’ve three properties on one supply, we already use a lot of electricity on site: 17-18,000kWh every year. And as we increasingly electrify our lives to reduce our gas and oil consumption, demand is only going to grow. By the time our holiday cottage guests are arriving in their EVs and we’re heating with pumps rather than oil boilers, our annual usage is going to be huge.

Which is why – as much as the outdated local infrastructure allows – I plan to at least double our current on-site PV generation, and optimise its usage with batteries (*edit – maybe not the battery bit). Not just because it makes financial sense, or because it feels good to be contributing to the renewable energy available to everyone else, but because there’s a strange thrill that comes from knowing your entire home is running off sunshine, and that a boiling hot solar-powered shower awaits at the end of the day.

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