Our Solis system, comprising solar panels and battery, was installed in June 2023, so we’ve now had a full year’s usage. That makes it worth checking on the experience: what was it like using the system, and how much electricity did it generate?
On the good side: the system reached the “fit and forget” stage reasonably rapidly. There was a certain amount of flailing around required to understand the electrity tariffs from our supplier, Octopus Energy, both for import (we’re buying electricity from the grid) and export (we’re selling excess electricity to the grid), followed by some experimentation to see what was likely to work best. But given that I started from a position of total ignorance, I don’t think the amount of hassle was unreasonable.
I’ve ended up settling on a plan called “Agile Octopus” for import, which varies the price considerably according to the time of day. The system seems quite good at avoiding importing energy in peak times, which means that the agile plan gives a reasonable import price: I’ve been paying around £0.165 / kWh (including 5% VAT). Since the import price varies between £0.156 and £0.31, I’d say the system is doing a good job here.
For export, however, I’ve settled on a plan called “Outgoing Octopus 12M Fixed”, which yields £0.15 per kWh: they have an agile plan, but that was yielding less revenue. The overall effect is that I’m only paying around 10% more for importing electricity than I am receiving when I export it.
In terms of how I use electricity, therefore, I’m now left with very little work. The car is set to charge at 00:30, when import tariffs are guaranteed to be around their lowest. The solar system’s 9.6 kWh battery does a good job of smoothing out everything else, so I’ve now stopped worrying about things like when’s the best time of day to put on the dishwasher, which was confusing, anyway, because it varies so much according to the seasons and according to whether the car needed charging.
The Solis system gives pretty good maxi-geeky graphs of everything it’s been doing. But to be honest, I hardly bother to look at them any more.
So much for the usability. But that leaves the elephant in the room: how much electricity are the panels generating, compared to what was expected when our installer did their estimates? Here, I’m afraid, the results are less favourable.
In the course of the year, the system yielded 5,259 kWh – that’s just 77% of what was predicted in our installer’s quotation. Now obviously, you expect there to be much variability according to the weather: last month, for example, the system reached its best ever yield of 885 kWh, which was 96% of the estimate. Still, I think I was hoping for closer to 85-90% than the 77% I got.
In terms of value, that was £866 knocked off my electricity bill for a system that cost £22,520 to install. The payback is going to be more like 20 years than the expected 13, bearing in mind that energy prices have come down enormously from when the system was installed.
I certainly don’t regret installing the system. It was the right thing to do my bit for the environment and I never expected giant savings. However, I won’t pretend that I’m not mildly disappointed that the numbers don’t look a bit better.
Of course, things could easily change. The weather’s been pretty poor in London over the last year, so a sunnier year could yield a lot more electricity. And sadly, there’s likely to be another spike in energy prices at some point in the system’s lifetime, in which case it will look like a sounder investment. We’ll just have to wait and see, and attempt to feel virtuous in the mean time. (Of course, I haven’t computed the carbon footprint of getting the system installed – that’s another conversation in itself).
Like many people of our age, we’ve become more and more conscious of climate change and the world we’re bequeathing our children. We can’t claim to be paragons of green virtue – we’re still doing far too much flying to even approach this – but we have been taking some of the right steps, and two years ago, we made the leap and abandoned the internal combustion enging: our first electric car, a Tesla Model 3 Long Range, was delivered exactly two years ago, on 30th November 2021.
Here’s a potted assessment, not just of the car itself, but of the experience of owning and running a Tesla. The short answer is that I’ve loved it: the car is great and the charging infrastructure has worked superbly. That said, there’s plenty to criticise in the user interface, not in the basic “iPad on wheels” concept, but in many details which are either misconceived or just plain don’t work.
The car
The biggest surprise about the Model 3 was quite how good a car it is mechanically. Leave aside the technology bluster, the computer screen, the blistering acceleration: the Model 3 handles better than any other car I’ve owned. You get this overwhelming feeling that when you turn the wheel to point the car in a particular direction, the car will follow immediately and precisely. There’s no resistance to your hands, there’s no lag, there’s no discernible roll of the car’s body, not the slightest hint of uncertainty. The response to your control is precise and immediate.
The big point of difference between the way you drive a Tesla and the way you drive petrol or diesel cars is the regenerative braking. When you start taking your foot from the accelerator, once you get to the point where the car is no longer accelerating, it gradually starts to brake. This means that you don’t really use the brake pedal at all in normal driving: your right foot acts as both parts of the “go faster / go slower” control. You might think this takes some getting used to, but I didn’t find this: I was completely comfortable within minutes. And once you’re used to it, that combines with the car’s basic responsiveness to make it a real joy to drive.
As has been well documented, the acceleration is phenomenal. I’ve only floorboarded the car once, largely to see what would would happen – and the thing that transpired was the certainty that my back and neck would start complaining if I did it regularly. Effectively, you have an on-off switch which says “overtake now”. Weirdly, this means that I drive the Tesla far less aggressively than previous cars: knowing that I can overtake just about anything else on the road at will means that I don’t have to do any of the jockeying for position that drivers often do. There’s never a need to drive up close to someone’s bumper to prepare.
The modern features you expect work well, like electronic locking and remote boot opening (or trunk, as Tesla insist on calling it – one day, they might do a British English option). Having the car warm up to the right cabin temperature at the right time every morning is a genuine luxury. Admittedly, it took me a while to get used to abandoning the car key and simply wandering up to the car with a phone in your pocket, expecting it to unlock. And finally, we find the car very comfortable – the seats are supportive and adjust in all the right places.
Our home charger
Range anxiety – or not
Our biggest concern about going electric was range anxiety: we do a regular round trip to Devon of around 250 miles each way and we’re often a bit pushed for time, so spending hours charging the car en route isn’t an option. So before buying the car, we did the trip in a rented Model 3.
What we found is that the Tesla Supercharger network works extraordinarily well. The chargers are very fast indeed: it’s rare for us to spend more than 20 minutes charging the car. That’s a very small overhead on top of the ten minutes we’d spend on a stop for the toilet and either a drink or a brief stretching of legs (we’re old enough that any long car journey carries the risk of our backs stiffening up). Our overall journey time to Devon hasn’t changed materially.
The ultimate test of range anxiety was the 2,000 mile road trip we did around France this July. Supercharger coverage in France isn’t quite what it is in the UK, so we needed a bit more preparation in the shape of acquiring a Chargemap card, which gives you access with a single RFID card to almost all the other commercial chargers around. Several of the hotels we stayed at recharged the car for free overnight, and there was a nice surprise when it turned out that the city of Aix-en-Provence provides free EV charging in their public car parks (although, admittedly, these are pretty expensive in the first place).
The car’s satnav is particularly good at this: dial in your destination (or even a couple of destinations ahead) and it will plan your supercharger stops. Then, when you’re on the road and approaching your supercharger, it will precondition the battery for ideal charging performance.
When touring, it’s worth noting that some supercharger stops are far nicer than others in terms of what facilities there are in the environs. Our stop in Valence was perfect because it was at lunchtime and the Novotel has a really nice brasserie. The Beaune supercharger allows a lovely 10-minutes-each-way walk into the city’s gorgeous old centre. The Amiens supercharger was decidedly less pleasant, with a lot of car park to walk through to get to the nearest toilet, in a MacDonalds. We discovered, rather late in the day, that an icon on your satnav allows you to find superchargers on your route so that you can Google them and see which ones look more salubrious; similar functionality is available on the phone app if you know where to look, off the bottom of the Location tab.
The user interface
If the Tesla is an obviously good answer to the “EV versus petrol” debate, its user interface is far more controversial. Some people will love the clean design that results from getting rid of as many manual controls as possible and putting them into a single iPad-like flat screen to the right of the steering wheel. For others, this will be unfamiliar and thoroughly unpleasant.
I’m somewhere in between. I’m perfectly happy to have all the controls on single flat screen, but there are an awful lot of things wrong in the way Tesla have done it. The good thing is that for most routine stuff, whether it’s setting up the climate control, checking tyre pressures or playing music from a bewildering variety of sources, the functions are easy to find and all work pretty well.
The single biggest problem is that I’m 65 years old, so I need reading glasses (but not distance vision ones). The speed at which my eyes can refocus between the screen and the road is limited and most of the fonts are so small that there’s a great deal of the UI that I simply can’t use while the car is in motion. A couple of months after I bought the car, Tesla relased an upgrade to allow me to select a larger font size, but that made only a modest difference.
This would matter less if the voice recognition worked better. Whether because of my British accent or vocabulary or because of something more fundamental, most of the time, I simply can’t get the car to understand what I’m saying, even for apparently simple commands like “windscreen wipers off” or “play music from Tidal”. Worse, the car often misinterprets my commands and does something completely unexpected, which you really don’t want to happen when you’re driving at speed.
Even at rest with reading glasses, the font size is also an issue when doing satnav searches: too often, you get a list of choices which are too long for the search results box and therefore get abbreviated with a “…” on the end. The effect is that you’re being presented with up to a dozen search results which look identical and which, on a bad day, can be several hundred kilmetres away from each other.
Future self-driving
For me, the most blatantly stupid aspect of the UI is the decision to devote the most important real estate on the screen – the third of the screen on the side closest to the steering wheel – to a 3-D visualisation of the car AI’s view of its surroundings – vehicles, pedestrians and cyclists, lane or edge-of-road markings. I assume that the motivation is to encourage the idea that the car is so good at modelling what’s around it that one day, we’ll have enough confidence to let it drive itself for us (if any Tesla employees are reading this who know better, feel free to disabuse me and explain the reality).
The trouble is, the visualisation is comically inept. Cars and lorries appear and vanish at dizzying speed. There’s no consistency I can identify as to when I’m likely to see pedestrians and when I’m not. The effect is the exact opposite of what’s intended: if the current display is the best model Tesla can create of the car’s surroundings, I’m not going to touch self-driving with a bargepole. It really irks me that this useless display is taking up the prime screen real estate where what I actually want is a large, easily readable speedometer, with some extras like the current speed limit, my journey time so far, expected arrival time and expected battery level at arrival in a large enough size that I can read them quickly. And I really would have thought that after going to the same car park barrier every day for a year, the car would have learned that no, I’m not going to drive straight into its box of electronics, and no, it doesn’t need to beep at me.
Some statistics
We’ve driven 9,920 miles in the two years we’ve had the car – a smidgin under 5,000 miles per year. The car reports our total energy use at 2,846 kWh, or 287 Wh /mile. At our current overnight electricity price of around £0.185 / kWh, that’s ust over 5p of electricity per mile, which strikes me as staggeringly good. To be honest, at our relatively low mileage, depreciation and insurance are going to be a far more significant cost than fuel.
For our France trip, a mixture of superchargers, other paid-for chargers and some free recharges, we ended up spending €0.09 per mile; if you ignore the free recharges, the figure goes up to €0.11.
The buying process
I need to mention that during the process of purchasing the car, Tesla’s customer engagement was dire. Sure, the online screen to set up your account and select the options you wanted worked fine. But navigating their phone system was horrific, there was really no idea given of when the car might arrive, and it wasn’t pleasant to discover that the pickup point closest to my home got mysteriously discontinued at some point during the ordering process. For a £50,000+ purchase, I’d have expected someone to answer the phones and give me a bit of TLC. They didn’t.
My overall impression is that their view of customer service is that it’s a cost centre: their strongest desire is to get you off the line and stop costing them salaries. Ensuring that you get a good experience to associate with their brand doesn’t seem to something that bothers them.
In summary
Quite simply, the Model 3 is the best car I’ve ever owned. It’s lovely to drive, staggeringly fast, practical, comfortable, reasonably attractive and its fuel costs are incredibly low (particularly since I have solar panels at home). Its charging network is second to none.
It would be great if Tesla had a serious rethink about their customer engagement and dealt with the dafter bits of the user interface. But I guess you can’t have everything. So far, therefore, all things considered, I’m not suffering from anything resembling buyer’s remorse.
The climate crisis has made me steadily more interested in reducing my carbon footprint by putting solar panels on our roof. As well as being the green thing to do, the recent turmoil in energy prices has made it economically sensible, so I’ve taken the plunge: last month, a substantial system of photovoltaic (“PV”) panels was installed on our roof. Should you do the same?
When specifying a solar energy system, there are many possible choices of exactly what equipment to install. The decision-making is complex because there are a lot of variables: how much electricity you expect to use (which will vary according to the time of day and the season), how you think energy prices will change, interest rates, whether you’re going to charge an electric car at home… The list goes on.
Solar installers will give you all sorts of models to show your return on investment: these can be somewhat rosy-coloured and generally only tell part of the picture, so I thought it would be a good idea to talk you through what the various components do and why I made the decisions I did, in the hope that it might help with yours (or just pique your interest). Most of what follows will apply regardless of which country you live in, but a few points will be specific to the current regulations in the UK.
First, you need an approximate scale of what you’re trying to achieve. Electricity use is measured in kilowatt-hours (kWh): roughly speaking, 1 kWh will light a small room for a couple of days, boil an electric kettle ten times or run a load on a small dishwasher. An average detached house in the UK uses around 10 kWh per day, according to OVO energy. Your daily usage should be shown on your electricity bill: ours was 17 kWh. I’m not yet totally clear about why we’re so far above average, but I’ll be working on it.
The major components of the system are as follows:
The PV panels, which convert sunlight into DC (direct current) electricity
The battery, which stores electricity for later use
The inverter, which converts the DC into the AC (alterating current) electricity that your house will use and also controls how much electricity flows to and from the battery
All of these cost serious money, so it’s important to get their amounts and sizes right.
How many panels?
A typical rooftop might fit between 10 and 20 410W panels – I ended up with 19, giving a maximum rated power output of 7.79kW. At first sight, that sounds like massive overkill: a maximum rated output of over 90 kWh on an average day with 12 hours of sunlight, compared to the 17 kWh that I use. But that’s wrong, for a variety of reasons:
In winter, days get much shorter than 12 hours
If the weather’s cloudy, the panels will produce a lot less than their rated output
In my case, because my roof faces east-west, only half the panels (roughly speaking) are operating at any time: the east-facing panels in the morning and the west-facing ones in the afternoon
There are inefficiencies in the system anyway
So far, the best that my system has managed, on one of the longest and hottest days of the year, was just over 40kWh (which was actually pretty impressive). The predictions in my quote are that I will be generating 61% of my total electricity usage: we’ll see how that pans out over the course of the year.
How big a battery?
Of course, you could operate without a battery at all, selling any surplus electricity back to the grid immediately and never storing it. The trouble is, in the UK at least, many of the electricity providers have been paying a pretty inadequate rate (as low as £0.05). This does seem to be improving, though: my provider Octopus have a tariff where they will buy my surplus power at a fixed rate of £0.15 per kWh, compared to the £0.49 they have been charging me for supply (which, to be fair, is going down to £0.31 this month).
Particularly since we have no idea how any of these tariffs are going to change, it therefore makes sense to have a battery big enough to store your usual overnight consumption (if you haver a smart meter, you should be able to figure out what this is, or you can let your solar supplier guess based on your total consumption and national averages). My battery has a capacity of 9.6kWh, which means that I will be exporting electricity back to the grid at the height of summer or when we’re on holiday and the house is empty, but not at other times. The batteries are modular and we might add another module to increase capacity in future, if it looks sensible to do so.
The inverter
In practise, the inverter will be the model with which your installer is most familiar. The decision to be made will be its capacity for delivering power, which needs to be higher than the maximum amount your system will generate at any one time. In the UK, there is an important limit: if your inverter is at or below 6kW, your application to join the electricity network is granted automatically; above it and you could suffer delays. My inverter is exactly at 6kW: because of my East-West facing roof, we can be sure that my solar panels will never deliver more than that, by a safe margin.
With your inverter comes a suite of software for monitoring how your panels are performing, how much electricity they are delivering, how much you are using, how much is going to and from the battery. Staring at the control panel on my phone was pretty addictive for the first week or two: the novelty is beginning to wear off now and I’m more inclined to let the system get on with it. Of course, it would be possible to spend hours analysing data and tweaking the inverter setup to the nth degree, most notably the parameters about how much it decides to charge the battery. I haven’t bothered to learn the tricks for doing this.
If your house doesn’t have much unused space, you may struggle to find a suitable place to locate the inverter and batteries. They generate a fair amount of waste heat, so you have to leave quite a lot of space around them. The place you choose has to be well ventilated. They won’t like being in direct sunlight (because of the risk of overheating). And you need to be able to run DC cables from them to all the panels, and AC cables to your consumer unit (the place where your electricity is distributed to the building).
Weatherproofed inverters do exist, which you can install on an outside wall. They’re more expensive, and you still have to be sure to keep them out of the sun.
You also generally need to ensure that they have an Internet connection available (different inverters handle this in a variety of ways).
Other ways of using surplus electricity
If you live in a very sunny place with a large roof, you might end up with a lot of surplus electricity. Here are some of the things you might choose to do with it.
Charge an electric vehicle – just to give you an idea of scale, the battery in my Tesla is 75kWh, nearly eight times the size of the one in my house. A typical 100 mile recharge is around 30kWh. But you could be generating enough power to make a sizeable dent in that, and/or you may have pretty low mileage anyway. In this case, you can buy a special purpose diverter (the popular brand in the UK is called a Zappi), which figures out, reasonably intelligently, when it’s a good idea to pump surplus energy into your car rather than selling it back to the grid.
Use it to heat water. In many UK homes, your hot water is powered by gas or oil, which is a lot cheaper than electricity, but the tank has an electric immersion heater for use as a backup. In principle, you could send the surplus electricity to your immersion heater to reduce your boiler’s gas usage, effectively using your hot water tank as a form of energy storage (the Zappi has a friend called an Eddi which does this). Trouble is, you need the right hot water tank for this to work: most domestic systems run on a thermostat, so unless you’re running your bath at exactly the moment when your electricity generation is high, the Eddi won’t contribute much.
Use it to power a heat pump. Air-sourced and ground-sourced heat pumps aren’t all that popular in the UK yet, because of a variety of difficulties. But the technology is improving, gas prices might get another upwards shock, and regulations discouraging gas usage could come in. As a result, heat pumps may become the way to go for more houses. If that’s the case for you, a considerably larger solar setup may be desirable.
The economics
If we’re honest, the economic case is a bit marginal, even with the recent turmoil in energy prices. My system cost over £20,000 and my installer’s fancy proposal-creating software gave a payback time of around 10 years, but that needed to be taken with a serious pinch of salt given that it all relies on assumptions about what was going to happen to electricity prices and interest rates (obviously, it matters whether you’re financing the project by borrowing or whether you have the money and it’s simply reducing your investment income).
So the chances are that you’re not planning to install solar for the economic benefit alone: you’re doing it at least in part because reducing your carbon footprint is a good thing in itself, or possibly because you live somewhere which gets a lot of power cuts, so having a high capacity battery gives you much wanted immunity to these.
Finding an installer
Even before the Ukraine war, the increasing desire to go green, together with the steady improvement in PV system performance, meant that there weren’t enough installers to meet demand. The energy price shock brought on by the war made the situation worse. So in the UK at least, good quality installers can pick and choose which jobs they do – which means that they’ll choose the ones they can do with least effort, ones close to where they’re based which don’t suffer from obvious technical difficulty.
Don’t be surprised if you contact an installer, get a first off quote which has taken them 10 mimutes with a bit of software, and if you then never hear from them again. I’ve had that happen twice, with a third attempt where an installer based somewhat far away decided that my job was all a bit too much effort and declined to continue. What finally worked for me was to identify a company who had done a successful installation at another house in my road.
Finally, once your system is installed and you get the right certificates to allow you to connect to the grid, you’ll want to choose the best possible tariff and get your installer’s help to programme the inverter to make use of it (for example, Octopus Energy tell me that for them, you want to avoid taking grid electricity between 4pm and 7pm). But that’s a whole other story…
So should you invest in PV?
Every situation is different: your economic forecasts and financial situation will be different from mine, as will your expected energy usage, the orientation of your roof, the ease or difficulty of access to it, the value you place on reducing your carbon footprint and many other things. And of course, there important things we don’t know: how energy prices will change, and how the technologies involved will change (hopefully to improve, but maybe to become more expensive if there are materials shortages).
Anyway, I’ve done my best to give you enough background to properly critique your supplier’s proposal and estimates and come to an informed decision. Good luck with your solar power journey!
Polything 