Posts tagged 'Climate change'

It's almost 12 months since we got solar panels and a battery installed on our house so I thought it would be a useful exercise to look at the financial results from them.

We have 5.2 kW of panels along with a 10 kWh battery. The panels are all on a South facing roof and we are also in the South of the UK so the setup is probably optimal for the best results in the UK.

First up, lets look at electricity taken from the grid.

This shows monthly electricity usage over time. Prior to the installation, electricity usage had been drifting lower but nothing spectacular. After installation, our average monthly usage is now about a third of what it was. In fact for about 6 months of the year we are drawing virtually nothing from the grid. When we are powered by the battery, there is still a small current being drawn from the grid (around 10W). I believe this is to keep the AC system in our house in sync with the AC from the grid. That means we are using about 10kW per month during the summer

Next, let's look at where our electricity is coming from

I guess the first thing to note is that we are producing more than enough electricity to meet our needs. Of course the problem is we have an excess during the summer and a shortfall in the winter. Whilst our battery is useful for covering our needs for 24 hours, it's not big enough to last for months (the problem for our future grid in microcosm). And although we can sell the excess back to the grid, they pay us far less than we pay them.

The other thing I've noticed looking at that is that the battery is a fairly efficient store of electricity, we are getting 87% of the electricity back out that we put into it. 

And one final point. A round 3MWh of our electricity came from our roof, but 1.35MWh of that came via the battery. Batteries are expensive but I think they are a vital part of any solar setup.

Now we can do some calculations. We currently pay 26.67p per kWh, so that 3MWh from the roof knocked off £800 from our annual bill. We exported 2.69MWh to the grid at 4.1p per kWh so we received £110 for it. So overall we have saved £910 in our first year.

People like to discuss a payback time for solar. We paid about £10,000 for our installation, so our payback would be about 11 years, which is a little longer than the time predicted by the installers. It's possible they also included inflation in their calculations or assumed a better rate for selling back to the grid. Now that I have a clearer picture of the excess we produce, I may look into other options for selling it. If electricity prices continue on their current upwards trajectory (thanks Donald!) payback will be even sooner

But to my mind, a better way of looking at the return is what could I expect to get from £10,000 invested elsewhere? If it was sat in a bank account, currently I might get 4% interest a year (not guaranteed). There are shares paying dividends better than that (again not guaranteed) but overall a 9% return a year seems pretty decent

July was hot, very hot, in the UK. It was also sunny and that led to a new record being set for solar generation, averaging over 4 GWs for the first time. Solar is really starting to tick up as a bigger contributor to our electricity generation, with the previous records being set in April and May of this year. 

Yesterday the UK managed to max out at over 15GW of electricity generated by solar power.

This was a day after the solar record had been set. That day was also windy and for a period we were only generating 0.4GW of electricity from fossil fuels, a new low and also a record low percentage of 1.2%

It would be nice to think it's our current government's positive attitude towards renewables that is helping us break these records, but in reality most of the infrastructure currently powering these records was started several years ago

Two days ago we broke the record for the amount of solar generated in a half hour period, managing 14.1GW. I'm not sure what new capacity has been added since last summer but I'm guessing a reasonable amount given how early in the summer we've managed to break the record from last year.

Then the following day, we produced the least amount of our electricity using fossil fuels in a half hour period, with just 0.85GW coming from gas. One day very soon the whole grid will be running on low carbon power for a short period of time. 

Update - The problem with reporting this data so soon after the event is that it sometimes gets updated afterwards. The data for the 7th of April was adjusted and the record for solar was broken yet again, reaching 14.4GW at lunchtime. 

On the 25th of March, we experienced a consistently windy day. Not only that, we had a decent amount of sunshine. This combination led to some records being broken. We managed to run the grid for half an hour with only 2.1% coming from fossil fuels. The average fossil fuel usage for the day was also a record at 6.3%. We are hopefully very close to running the grid entirely on clean energy when conditions are favourable. We also smashed the record for low carbon production, hitting a maximum of nearly 40GW and averaging 30.8GW over the day. Finally, we also generated the most power from wind in a half hour period, hitting 23.88GW.

Also of note is the difference in the price of electricity between the day (when renewables were dominating) where prices were less than £20/MWh and the evening (when more gas generation was needed) and prices shot up to over £120/MWh

It's almost the end of the year so I thought I'd take a look at how the energy transition is going in the UK. You can find the data here. 

For the second year, wind is our biggest source of electricity, rising slightly from an average of 9.4GW to 9.8GW. I expect wind will continue to be our biggest source for the foreseeable future, unless a new clean, cheap energy source appears. 

Solar is still a small part of our energy mix, but increased from 1.6GW to 2.1GW. That's actually a big increase compared to previous years and I suspect solar could become a much bigger part of our electricity supply, since it produces lots of power in the summer whilst wind excels in the winter.

Other good news was coal producing no power at all for the first year since electricity generation began in 1882.

The bad news was there was also an increase in electricity production from gas and also a small increase in the carbon intensity of electricity generation. I suspect this is due to electricity demand starting to increase and the build out of renewables not keeping up.

Yesterday, UK wind generation hit a new milestone of 23GW for the first time ever, a year to the day since we hit 22GW and smashing the record set a few weeks ago, maxing out at 23.8GW.

UK electricity generation on 5 Dec 2025

The data on my UK electricity generation page is automatically updated every day. A couple of months ago I was looking at the latest update and noticed some of the top level records had changed but not on the previous day. It's not unusual for recent data to get updated but now the data was saying a number of electricity generation records had been broken on 26th June 2023, over 2 years ago.

Initially I thought this was an error in the data and it would be corrected at some point but here we are 2 months later and the data remains the same. So what's up? Why was the data updated and why so long after the actual event?

I did some Googling for uk electricity generation 26th June 2023 but nothing turned up. I also did a search on Bing and my page came up as the top result so that's nice but it couldn't tell me anything special about that day. I even tried asking ChatGPT, which proved even less useful. 

So all we can do is look at the data for the day and for the previous day. The 25th was a good day for solar and wind generation and as the sun disappeared, gas started to ramp up as it usually does. But at 6pm, gas generation started to fall fairly dramatically until 10pm. Then it continued to fall but at a much slower rate. This continued until 5:30am on the 26th, when gas reached virtually zero generation. After this, things fairly rapidly returned to normal.

So what happened? Why did gas generation reach a new record low that we've never got close to again? One possibility is that this a data glitch, but why was did it appear in the data set two years after the event? One reason this looks like it could be the correct answer is that it doesn't look like we were actually producing enough power during the evening of the 25th (although it is possible we were importing more than usual).

But a more interesting theory is that this was actually an experiment to see how the grid coped with mostly clean energy sources. It's my undersanding that electricity generation that involves turbines helps keep the grid's AC frequency in sync, so there have been some questions about how we deal with that when most of our electricity comes from renewables. The fact this weirdness happened in the middle of the night and the gradual withdrawal of gas from the mix gives some credence to this theory. And if that is what happened, the fact we haven't come close to these low levels of fossil fuel usage again may suggest the test was not completely successful.

Anyway, I am going to ask NESO what is happening with that day's data and will let you know if I get a response.

Update - I got a response from NESO. The data is wrong, nothing of interest happened in the world of electricity generation on 26th June 2023. 

The main reason I set up the UK electricity generation page was to see the progress we are making on the road to a clean grid. One of things I was hoping to see was fossil fuels get pushed off the grid completely for a short period of time. There has been talk of that happening some time this summer, but it hasn't happened yet and the lowest levels for fossil fuel use were over a year ago.

There may well be sound reasons for this but it is somewhat disappointing. So I came up with my own statistic to show we are making progress. Count up the time we are producing more than 30GW of power from low carbon sources, because 30GW is the UK's average electricity demand. I'm only including wind, solar, nuclear and hydropower in this calculation because I'm not a fan of biomass. And in June 2025 we managed to achieve this for 27 hours in total, a new high. This broke the record of 15.5 hours set the previous month. 

If you squint, you can see the UK's clean grid coming over the horizon. 

UK electricity generation on 22nd May was fairly typical for a reasonably sunny summer's day.

Gas generation was low in the middle of the night because demand was low. As the day started, demand increased and gas generation increased but was limited as solar generation ramped up. Then as solar dropped off but demand remained high in the evening, gas generation went up yet again. You can see this repeating on most sunny summer days.

Now imagine we had twice the solar capacity we have today. We'd actually be able to turn off gas power stations in the middle of the day. That would be a pretty big deal in itself. But now imagine we had enough battery capacity to store the excess solar energy so we don't need to turn the gas power stations on for some of the evening hours. Keep on ramping up solar capacity and we'd eventually be able to store enough electricity for the evening and the nights, refill them during the day and keep going. We could go days without using fossil fuels.

Anti-renewables people often say "what happens when there's no sun or wind?". Even reasonably pragmatic people will say something similar. It's not an unreasonable point to make, in the middle of winter we can go days or weeks with little sunshine and not much wind and we'd need an absolutely huge fleet of batteries to deal with that scenario. But the batteries required to deal with getting from one sunny day to the next is much smaller. Even in the famously grey and gloomy UK, it's probably something that's worth doing. 

There's a politician in the UK who has a simple solution to every problem. His last simple solution to our problems was to leave the EU, it would appear that didn't fix everything because he's back with some more simple solutions. One of them is to dump renewable energy and get back to good old reliable fossil fuels. Like with all his solutions it's based on a half truth at best. This site gives a breakdown of where the money from our electricity bills goes and in 2025 about 20% of our bills go on some kind of renewables subsidy. But go back to 2022 and closer to 5% of our bills were going to renewables because the price of gas was driving the wholesale price of electricity and gas prices had shot through the roof. Even in 2025, the biggest part of our bills comes from the wholesale price of electricity, which is still mainly driven by the price of gas.

But what will happen in the future as more and more renewables come online? We can make a good guess by analysing the generation data from NESO and the price data from Exelon. I've taken the data for 2025 and here's a graph of electricity price against the percentage of fossil fuels being used to generate it.

That big spike in price between 50 and 60 percent squashes the graph so it's difficult to see what the trend is from this graph, but I put it in because it show a couple of interesting things. First is that the price of electricity can fall below zero, but it only ever happens when we have a lot of renewables online. I guess it might be a good time to invest in batteries, charge them when prices are low or negative and and sell the electricity when prices have gone back up. The second thing to note is the insanely high prices when we don't have renewables available. That's gas fired power stations making a killing because they can...

So if we put this data in buckets of 10% we can get a clearer picture of what's going on

This makes it pretty clear that as less fossil fuels are used to produce electricity, the price drops. Building more renewable capacity and batteries will put us on the left of the chart more frequently so prices in general should be lower. I will caveat that statement by saying I am no expert on the workings of the electricity market, so can't guarantee things are that simple...

Contains BMRS data © Elexon Limited copyright and database right 2025

Supported by National Energy SO Open Data

I've added a new page to the website that provides some data on UK electricity generation. There are a few hopefully interesting graphs and some monthly CSV data you can download. It gets updated daily so you can see how the energy transition is progressing. Let me know if you'd like to see anything else included

There is a problem with renewables. They are meant to be cheaper than fossil fuels, but as we add more of them our electricity prices have been rising. This has led to some of our politicians claiming the price rises are due to renewables themselves, which seems to make some sense. Doubling up our electricity production so we have renewables for when it's sunny and/or windy and gas/nuclear for when it's not seems like it could be a more expensive option. So let's not worry about climate change and don't bother building any more renewables. Right?

Except that's not what's happening. With our current level of renewables, we are never turning off some of our gas powered stations. And electricity in the UK is priced at the level of the most expensive producer, so it is always tied to the price of gas. And the price of gas shot up after Russia's invasion of Ukraine and is still higher than it was previously.

But, perhaps reasonably, some people will be sceptical of this explanation until they see their electricity bills falling. So I thought I'd try to figure out when we should see gas falling out of our generation mix. I downloaded the historic data from NESO and did some simple analysis of it

For every month, this shows the minimum and average usage of fossil fuels over a half hour period, both with a linear trendline, which mostly fits the data sets.

The first milestone we should hit is a period of 30 minutes where we don't use any fossil fuels. The linear trendline suggests we should have already hit that milestone, but the drop seems to have stalled over the last couple of years. Maybe someone with a better understanding of the National Grid can explain why that has happened, but it seems like something we'd want to happen as quickly as possible from the consumers' point of view. I think that possibly from the government's point of view it may not be something they'd like to happen too soon. From my understanding, renewables get a fixed price for their electricity, if the wholesale price goes below that price, the government pays the difference. 

The next milestone will be when the average fossil fuel usage gets to zero. That trendline is looking linear at the moment but I'd expect that to flatten as it approaches zero. In long periods of low wind and sun, storage is not going to be able to meet demand. So maybe it's better to look at renewable electricity production. 

The NESO low carbon figures include nuclear, wind, solar, hydropower and biomass (eugh) and the maximum and average are displayed above. The UK typically requires about 30GW of electricity and the trendline suggests we'll reach that average level in about 2039. Then we'll be producing enough electricity by renewables to meet our needs but some of that will be getting exported when we are producing too much so we will probably still be using gas for some periods. My understanding is that is the definition the government is using for a green National Grid which they hope to reach by 2030, so our renewables output is really going to need to step up a few gears in the next few years to reach that goal.

Supported by National Energy SO Open Data

This seems like a big milestone. Electricity produced by renewables in the UK in 2023 is higher than electricity produced by fossil fuels. Hopefully the wind will continue to blow for the rest of the year and keep it that way. Source

Before this summer, climate change had always seemed a rather abstract concept. I knew it was happening and I knew we had to do something about it, but it appeared to be a gradual process that would take decades to play out.

Then large parts of the world started burning. And other places were suffering from catastrophic flooding. As I read about these disasters, the algorithms decided to show me even more related stuff, like the graphs of sea and land temperatures and the climate records being broken on a daily basis and the future started to look increasingly dark.

I went in search of positive climate news and the increasing use of EVs along with the increasing use of renewables to generate electricity gave me some hope for the future. This post gave me the idea of automating the calculation of the equivalent MPG of an EV. I liked this comparison since we are all familiar with the MPG for a fossil fuel car. So here you can calculate the equivalent MPG in terms of emissions and also cost.

Plugging in some numbers for the UK suggested owning an EV is a good thing for the environment and for your pocket. Even for the dirtiest countries (I'm looking at you Poland), running an EV is probably equivalent to running a fossil fuel car and will only get better as we transition to cleaner sources of energy. Of course, not using a car for journeys is an even better option