A few people have asked me for advice about getting solar panels since I posted about our newly installed system.
There is lots of general advice out there, and installers will of course look at your particular situation.
For instance, Artisan Electrics has a video with good advice on the topic, which mentions a lot of the practical considerations.
There are lots of things to think about, like what roof you have and whether it is in the shade at all. Having some shade isn't a dealbreaker (you can always get a micro-inverter for each panel), but you could have a look at your roof at different times of the day to see whether any nearby trees or rooves cast shade.
Essentially, you want to get an MCS approved installer. They have to abide by high standards and only MCS installed systems can generate export payments. You certainly want to get paid for your excess if you are having a large system installed.
I found the sales people generally quite useful for reviewing the options and coming up with a proposal they believe is in your financial interest, based on their own assumptions.
However, there are a few things that installers might not flag up to you.
Future proofing?
As I mentioned in my previous blog, the focus tends to be on covering self-consumption. This is because you can be sure that you will save money on your electric bill if the solar (or solar and battery) covers that.
After all, the export payment rate has been very low in recent years, so there has been little incentive to use your roof to supply the grid.
However, there is no way to truly work out the payback time for a solar system - it depends on too many unknown future factors. How much will your electricity bills be in the future? What will your demand be? What will the export price be? Nobody knows for sure - certainly not me!
Higher rates in the future?
However, that might not always be the case. New tariffs like Octopus' Flux tariff are offering rates several times that of the longstanding (but paltry) Standard Export Guarantee. However, these higher rates aren't guaranteed and the entire tariff might be withdrawn at any point.
Nevertheless, if you look at all the plans to build solar farms and the controversy raised about them, it seems like using rooves is much less controversial. If all rooves were covered in solar and every house had a battery it would really help the country continue to run on clean energy through windless days after all.
I certainly can't guarantee what export rates will be in the future, but I expect that if you've got a battery you will be able to use this for energy arbitrage - buy when the price is low and sell when it is high.
Higher electricity consumption in the future?
But the other reason to think beyond your current use is that your use might increase in the future.
Obviously, we are all looking to get more energy efficient as time goes on. LED lightbulbs use a fraction of older types for instance.
However, that is just part of the story. The other side of net zero is that we need to electrify energy previously provided by fossil fuels. In the UK that means that your car, heating and hot water will be electric (the latter two ideally with a heat pump).
These will require a lot of electricity to replace the petrol and gas. The usage won't necessarily perfectly line up with solar production - your car might be out in the middle of the day in the summer and your heat pump will be working much harder in the colder winter months when the solar production is much lower.
Nevertheless, having your own generation to assist in these things will be useful, and the case for a home battery and solar will increase the more that your activities are electrified.
More or less?
Overall - my feeling is that you can't really have too much solar generation (unless you have a REALLY huge roof that could fit loads of panels).
Of course, you can add to your system later. There is a case for getting something to start with and building from there. However, a lot of the cost of installing a solar system is the labour and scaffolding rather than the number of panels (which are about £200-£300 each)
I am glad I pushed for a slightly larger system (16 panels when a lot of the quotes were for 20), though I now wish I had budget for an even larger one.
Too small an inverter?
I've given one reason why you might be pushed towards too small a system.
One thing to be aware of is that the regulations have created an incentive for installers to install smaller inverters, which might also push them to recommend fewer panels for your system.
The inverter is the crucial part of any solar system - it converts the DC power from the panels to the AC power used in your house and the grid.
When installing the system it is necessary to inform the local Distribution Network Operator (DNO). There is a process to do this.
For a smaller sized inverter (under 3.68kw) it is only necessary to inform the DNO of the installation (G98).
Over 3.68kW?
For a medium or large inverter the installer has to seek approval (G99). Any decent company should include this service.
However, this process takes time and the outcome is not guaranteed - you might be told that the local network cannot cope until it gets upgraded in the distant future, or, that your own supply line needs to be upgraded (though this is unlikely unless you are having a lot of panels installed).
More importantly, as well as time spent on the process, it also costs money - companies have to pay to go through this process.
For this reason, it is conceivable that companies would push customers towards a smaller system, of around 12 panels or fewer, even if they would do well to get a larger one.
Essentially, this regulation has created an incentive for installers to propose solutions of a particular size. I expect that many people will end up with systems sized at this level because of this regulatory quirk.
Fortunately, although I wasn't really aware of this issue when I ordered my system, I did notice that a 5kW inverter had some advantages of a 3.68kW one AND was virtually the same price. I therefore mentioned this to my installer, who agreed to install the 5kW.
This was a risk for the installer, but I have got a much more appropriate system as a result.
Plus, if I do add a few more panels in the future the inverter will be able to process the higher peak energy created, which a smaller one wouldn't manage.
Final thoughts
Overall, I am a huge advocate of solar systems for climate mitigation reasons, but they also make a lot of financial sense.
There is a lot of good advice out there from people who know their stuff. There are several You Tube channels on the topic such as Gary does solar and Tim & Kat's Green Walk.
Most installers will give you good advice and consider the relevant factors.
However, I wanted to flag up a few things that might lead installers to push people away from using their roof to its ideal solar potential.
