August 2020 was pretty dull. Coronavirus was still doing its (dull and boring) thing. And the sun only bothered to shine for 136.3 hours in the North East of England. So that meant, inevitably, a pretty dull and underproductive month for our solar micro-generation. However, the Tesla Powerwall domestic battery enabled substantial savings by ‘peak-shifting’. Additionally, the gradual easing of lockdown meant we drove more miles in the EVs. The table below summarises the data.
Off-peak grid energy imported
Peak grid energy imported
Peak grid imports avoided by using stored energy from Powerwall battery
Total energy consumed (domestic consumption and EV charging)
Net cost of grid energy, incl standing charge, net of Govt payments for solar
Cost of 1,162 kWh at UK ‘Big 6’ average rate per kWh
Saving on 1,162.6 kWh vs UK Big 6 average rate
Total range charged to EVs, from solar and off-peak grid imports
Actual cost of solar + off-peak grid energy to charge 1,185 miles
Fuel costs to drive an ICE car 1,185 miles using @35mpg & £1.32/litre
Saving on 1,185 miles vs cost of motor fuel for same mileage
Electricity and motor fuel savings in month
CO2 savings on domestic energy by using solar & 100% renewable grid energy
CO2 savings on 1,185 emissions-free miles versus ICE @ 125.1 g/km
Total CO2 emissions avoided in month
August 2020 Summary
Here’s the link for detailed monthly performance report in PDF format. You can also get the report by clicking the calcographic below.
Follow this link to view the in-month and cumulative impact of August 2020 on payback of the capital costs of our solar, battery and EV charging installation
July was a pretty good summer month, by North East England standards. Key results are as follows:
1,215 kWh total energy consumption.
816 kWh solar
314 kWh off-peak grid (100% renewable supplier)
86 kWh peak grid (100% renewable supplier).
Taking into account the minor Government subsidy we receive for solar generation, we once again had a negativenet cost of energy, paying minus £5.36 for the month’s electricity.
We fuelled our two EVs (and a Renault Zoe we had on test for the first half of the month) for a total of 758 miles in the month. The ‘fuel mix’ going into the EV batteries was 360 kWh solar and 97 kWh off-peak electricity. This blend produced a total electricity cost for 792 miles of EV motoring of £4.84, or 0.6 pence per mile.Using our normal comparison with a 35mpg OldTech car fuelled at the long-term average of £1.32 per litre, we saved £262 fuel costs in month.
The total net financial benefit in July was £384.93, made up of these £262.08 fuel savings and the £122.86 difference between the price we would have paid for 758 kWh of domestic energy at ‘Big 6’ utility company rates (£117.50) and the net minus £5.36 we actually paid.
Emissions avoided in the month by the combination of solar generation, 100% renewably sourced grid supply, and 792 miles of zero emissions driving totalled 378 kg.
Click the graphic below to download the full report in PDF format.
Other than the ongoing mass death virus thingy and associated economic implosion, June 2020 was an exceptionally pleasant month in the UK. As anyone with solar panels will tell you, it was very, very sunny indeed towards the end of the month, although the MetOffice recorded only about 165 hours of bright sunshine in June in our region, compared to the positively Arabian 269 hours which had beaten down on us in May.
Whatever the Bracknell stats geeks say, we ended up with enough sunshine to produce another month with negative cost of energy. As the calcographic below shows, although we consumed nearly a megawatt of electricity for domestic use and charging EVs during this (still a bit lockdowny) month, we actually ended up £12.19 better off in net terms at the end of the period.
The £36.12 Government payment for 740 kWh of solar generation was more than the £23.93 cost of importing the meagre 225 kWh of grid electricity we did not generate ourselves in the month, which includes £7.50 of ‘standing charge’ fixed fee for grid connection at £0.25/day.
Our two EVs were charged roughly 70% with solar (195kW), plus 30% (82kWh) with zero carbon off-peak energy supplied at only 5p/kWh on the Octopus Go tariff overnight rate. Coronavirus ensured that June 2020 was still a very travel-restricted period, so we only covered 593 miles. However, even over this relatively small mileage, that still added up to fuel savings versus petrol/diesel ICE cars of £160.40. The electric ‘fuel’ for the EVs cost us just £4.10 in the month, which works out at only 0.7 pence per mile! It would have cost us £164.49 to travel the same distance in ICE cars, using our standard mpg calculations.
We also won big-time on our 719 kWh domestic consumption. 76% (545 kWh) was solar, including 374 kWh which was stored in the Powerwall stationery battery during the sunshine hours and used in the evenings. The remaining 24% (173 kWh) was zero carbon source grid electricity from Octopus. And over half of the grid imports were stored during the super-cheapo off-peak hours into the Powerwall and discharged at zero additional cost to us during the peak period.
Taking into account the solar generation payment we received from Government, our 719 kWh of domestic energy cost us minus 1.7 pence per kWh, making minus £12.19 net. If we had bought those kWh at UK ‘Big 6’ average rates, we would have paid £111.37. So that’s a net financial benefit of £123.56 for domestic energy consumption.
Putting domestic energy savings and motor fuel savings together, net financial benefit was £283.96 in the month of June. And the planet was 298.6 kg of CO2 emissions better off too.
Please click the image below for a downloadable PDF of the detailed monthly report. The impact of this month on financial payback of system costs is here.
This entire post is available as a downloadable PDF here, if you prefer.
There have been some memorable scorelines over the years. The two most important of all time being, of course, Nottingham Forest 1 : Malmö 0 and Nottingham Forest 1 : Hamburg 0, to win the 1979 and 1980 European Cup finals. And, yes, I’d really like East Fife 4 : Forfar 5 to actually happen (and not on penalties, 22/07/2018 doesn’t count).
Another result that really matters occurred in May 2020. A couple of things came together. The sunniest spring on record in the UK, with May’s MetOffice stats confirming a stonking 269.6 hours of bright sunshine in East and North East England, our area. But, on the downside, the Global Zombie Apocalypse Megadeath coronavirus pandemic continued to do its thing.
So, whilst global megadeath was an unreservedly bad thing, on the brighter side, May 2020 gave UK (and the rest of the world) a glimpse of how a low carbon future will look, painting in even more vibrant colours the picture that had begun to emerge in April, the first full lockdown month.
Pandemic meant pandemonium for the economy. And that meant massively lower demand for energy due to shutdowns for business and lockdowns for the people. By consequence, that also meant massively less mileage driven on the roads.
Unless, when it came to driving, you were in the minority which thought might be a good plan to drive a car load of infected people 200+ plus miles from London to County Durham, and then take a 50 mile round trip ‘to test your eyesight’ before driving back to London to lend your moral authority and public credibility to the Government’s campaign imploring citizens to act responsibly. Honestly? You couldn’t make it up for a satirical show.
Now, come to think of it, where’s Malcolm Tucker when you need him? I can barely imagine the weapons-grade Glaswegian invective that would have eviscerated any Downing Street adviser who had decided, erm, to drive a car load of infected people 200+ miles… You get the picture. Over to you, Armando.
Simultaneously with massively lower demand, the sun helpfully shone and the wind generously blew, which led, at 12:20 on 24 June, to a record low carbon generation mix of only 60 g CO2 per kWh) at National Grid level. You can get the Grid Carbon app here.
A tip of the hat to Patrick Erwin for spotting this and posting on LinkedIn. Responding on that platform, it occurred to me that this was a very clear view of the COVID/Carbon connection in action.
How curious it is that something as ruthlessly fatal to humans is actually brilliant for the health of humankind’s home planet.
Basic message: if everybody and everything slows down, the generation mix goes supergreen.
The real, structural, challenge will be keeping it green when the economy re-ignites.
So how did May 2020 play out at domestic level? The calcographic below summarises how it went for us. We hope you like the new graphic style. Click the image to get a zoomable high resolution PDF.
For those who prefer narrative to calcographics, the main highlights of the month’s performance are summarised below:
We used 1,231 kWh used in total, of which 960 kWh (78%) was solar. The remaining 194 kWh were grid supplies using Octopus Energy’s ‘Octopus Go’ tariff, which incentivises consumption of dirt-cheap ultra off-peak energy for recharging our Tesla Powerwall and two EVs between 00:30 and 04:30 in the small hours period of very low grid demand. The month included seven energy-intensive kiln firings for Anne’s ceramics business, which we timed to soak up solar surplus and energy stored in the Powerwall.
We only drove 439 miles in the EVs in the month, due to lockdown. 100% of those miles were fuelled with our own solar energy plus (a tiny) 16 kWh of zero carbon grid energy that Octopus actually paid us to use in order to keep renewable generators switched on during the record low demand at 05:00 – 07:00 on Bank Holiday Sunday morning.
Including the small quantity of ‘get paid to use’ kWh over the Bank Holiday, and the minor Government subsidy for solar generation, the results were as follows.
Domestic consumption actually cost minus 2.192 pence per kWh, giving a negative cost for domestic energy consumption of minus £26.98 in the month. If the same kWh had been purchased at the UK average cost per kWh, we would have paid £190.74. Hence the saving versus UK average for domestic consumption is £217.71.
The 439 EV miles actually cost us minus 79p in electricity in total (-£0.79). Using our standard calculations, the petrol cost of those 439 miles would have been £75.14 in total. Hence the overall financial saving versus a conventional car was £75.93.
In total, in May 2020, we met all our domestic electric requirement and drove 439 miles for an actual cost of minus £26.98. That is to say we were just under £1 a day better off for using energy, whilst causing zero emissions.
The total saving, versus the UK average cost of all electricity used and driving 439 miles in a petrol car, was £293.64.
That energy performance also produced a total saving of 310kg in carbon dioxide emissions versus the carbon impact of using grid energy at UK Grid average carbon intensity and fuelling and internal combustion engine (ICE) car. It’s worth noting that the emissions saving was lower than usual, due to the lower EV mileage in the month. This is because it is miles driven in EV, versus the carbon impact of covering those same miles in an ICE, which causes the greatest reduction in CO2.
With a superb 223.5 hours of sunshine, April generously bestowed lots of free kWh on the solar panels. But coronavirus ungenerously killed tens of thousands in the UK. Which meant lockdown. Which meant very little driving in the EVs. Which meant the vast majority of our stored energy went into domestic load via the Powerwall.
On the upside, “one permitted exercise a day” meant around 500 miles in early April on the eBike, through the beautiful countryside around home.
All was going brilliantly, until 14 April, when Alan got hit from behind on the back of the helmet by the wing mirror of a delivery van doing that COVID-driving thing; assuming there’ll be nothing else on the road. Long story short: two spinal fractures, two broken hands and face mashed up a bit. And the van driver didn’t stop. Alan found some minutes later unconscious on the road. On the upside: had the odd experience of being the only non-COVID patient in the A&E hospital. 2 consultants and an entire nursing team. On the downside: bike knackered. On the really big upside: one of the A&E consultants said that 8 out of ten cyclists who have that accident end up under the wheels of the vehicle which knocked them off. So, really glad to be alive!
So that’s why April’s performance report is a bit late getting to you folks. Apologies; better late than never.
833.3 kWh solar generation; of which
307.3 kWh charged into Powerwall storage battery for domestic use;
526.0 kWh used at time of generation for domestic load or charging EVs.
184.3 kWh off-peak grid electricity consumed; of which
116.7 kWh was charged into Powerwall storage battery.
41.2 kWh peak electricity consumed.
Total cost of grid electricity purchased: £22.04
Total Government payments for solar generation: £40.63
Net overall cost of electricity in month £-18.59 (i.e. negative 1.5p/kWh).
Total consumption in month: 1,175 kWh
Cost of 1,175 kWh at UK average cost per unit: £182.20
Actual cost of electricity, including standing charge, net of Government payments: £-18.59
Total savings on electricity costs alone vs UK average: £200.79
Total savings, including the cost of petrol saved by driving EVs: £271.26
However, lockdown and injury meant very little driving in month. Only 424 miles. Hence a lower than normal emissions saving of only 297kg carbon dioxide avoided, compared to roughly 3/4 tonne in a typical month. Basically, we didn’t do very much green-powered driving, for which hydrocarbon fuel would otherwise have to be burned. So less planet-saving by us. But there was a huge amount of planet-saving by the coronavirus: kept billions of cars off the road worldwide and grounded global aviation. Silver lining or what?
Now, Mr Corona, thanks for coming in to HR for your performance review.Let’s start with the positives.No question about it, you’ve made the biggest contribution in modern history to solving the climate crisis.So an outstanding A+ on that score.And you might even put Ryanair out of business, so maybe humanity will have another reason to thank you.But, I’m afraid I am going to have to issue you with a formal warning about thisglobal zombie apocalypse megadeath thing you’ve been doing.It’s just not acceptable and you’ll have to stop…
Back in locked down Northumberland, only a tiny fraction of our EV mileage was ‘fuelled’ with overnight cheap rate electricity, for a total cost of £2.29 in the month. The rest was solar, costing £0. So that gave us an overall average fuel cost of £0.005 (half a penny!) per mile.
Overall that’s a saving of £70.46, versus the £72.75 cost of fuel to drive an internal combustion engine (ICE) car for the same 424 miles. On that basis, ICE fuel costs would be around £0.17 per mile.
That makes our largely solar-powered miles around 34x cheaper than petrol! So feeling super-smug this month. Will aim for absolute zero fuel costs in May.
As usual, click the image below to download the full monthly report. Payback economics are here.
The big news in March 2020 was, of course ‘Black Death 2.0’ (aka COVID-19), bringing death, fear and economic implosion on a worldwide scale.
On the upside, it was an exceptional sunny month! Only March 1929, 1995 and 2003 have produced more hours of sunshine in the North East of England since MetOffice records began (in 1929). So a juicy 521 kWh of free electricity fell out of the sky and into our house, domestic storage battery and two EVs.
And lockdown meant that, in the latter part of the month, we hardly did any mileage in the cars, so we used less off-peak electricity on the exceptionally good value Octopus Go tariff.
Headline summary data (rounded to nearest whole number) is listed below. Click the image at the end of this post for the usual detailed PDF of the month’s performance. And click the banner here for a referral link that will save you (and us) an additional £50 on their dirt-cheap overnight energy.
Solar generation: 522 kWh, of which 177 kWh was stored in the Tesla Powerwall domestic battery and discharged during peak hours.
Tesla Powerwall discharge of stored electricity: 546 kWh, of which 177 kWh came from solar and 369 kWh from off-peak electricity.
Octopus Go off-peak grid supply: 802 kWh, of which 369 kWh went to Powerwall and 433 kWh went to charging the two cars.
Peak grid energy consumed: 180 kWh.
Total financial benefits in month: £421 including motor fuel saving.
Total CO2 emissions savings in month: 570 kg.
This rather helpful month has helped keep the whole system on track for a rapid payback. Running totals are here. However, if the COVID-19 lockdown persists for a prolonged period over the summer months, a rather counter-intuitive effect will become apparent. If we drive very few miles in our EVs, then it is likely that they can be entirely ‘refuelled’ from completely free solar energy. The payback equation subtly alters:
Payback to date has been on the basis of reasonably high mileage, which is refuelled using a blend of solar and (quite a lot of) off-peak electricity. There is massive delta between the cost of that electricity blend and the cost of petrol to propel a conventional car over the same mileage.
In lockdown, far less miles will be driven, which will mean that this delta does not come into play, as the vast majority of charging is likely to be solar, at £0 cost.
Our savings, versus petrol for a given distance, are likely to be less overall. In short driving “a few miles at absolute zero energy cost” is likely to deliver less of an overall benefit than “many miles at a very low blended energy cost.” The effects will play out over the next few months.
During this month, Alan also published an article analysing the major upgrade to the package of tax breaks and other incentives the UK Government is introducing on 6th April 2020 to encourage the uptake of electric vehicles.
February 2020 was a month of severe storms (Ciara, Dennis and Jorge) which brought widespread flooding and general misery to much of the North of England. Fortunately, all the solar panels stayed firmly attached to the roof and even managed to generate a bit of electricity on the few sunnier days between the downpours.
So, once again, the bulk of the emissions-reducing and cost-saving contributions came from the Octopus Go tariff, providing dirt cheap, green-sourced, electrons to the two EVs and the Powerwall between 00:30 and 04:30 every night. Click the button below if you’d also like to sign for 5p/kWh electricity sluiced into your EV or domestic storage battery in the small hours.
As usual, the detailed monthly performance report is available by clicking the image at the end of this post. The headlines are as follows.
£460 financial benefit in the month. This saving compares the cost we actually paid for all the electricity we used (overwhelmingly during the night on the Octopus Go tariff to charge the cars and the domestic storage battery) versus the cost we would have paid at the UK average rate per kWh. It includes a saving of £232 for the petrol we did not have to buy to drive the 1,545 miles charged to our EVs during the month.
404 kg of CO2 emissions avoided by using only 100% renewably-sourced electricity versus the emissions that would be caused by using electricity produced at the UK average generation mix of renewable and carbon-based sources.
311 kg of CO2 emissions avoided by using only 100% renewably-sourced electricity to power 1,545 miles of motoring in EVs, versus the emissions that would have been caused by covering the same distance at the UK average g/km CO2 emissions rate.
January in Northumberland is never a good month for solar panels. The earth does the tilting on its axis thing, which means the sun barely creeps above the horizon, except for a couple of hours around midday. In short, one does not feel particularly illuminated in January.
And, speaking of a lack of enlightenment, January 2020 finally inflicted Brexit upon the UK. It remains to be seen what the effects will be in GreenTech and sustainability. So far, the Government is making all the right noises about pressing ahead towards Net Zero by 2050. Time will tell.
Meanwhile, on the much smaller scale of photons hitting our roof and electrons getting stored in the domestic battery, the two EVs and the eBike, only 67.3 hours of sunshine in January 2020 meant that we were once again, as in December, heavily reliant on the Octopus Energy Time Of Use Tariff to fill up the various batteries with cheapo energy in the dead of night. Click the button below if you’d also like to sign for 5p/kWh electricity sluiced into your EV or domestic storage battery in the small hours.
The last month of 2019 was very dull in North East England for the first three weeks, before a sunny period between Christmas and the New Year rounded things off. Overall, the Met Office recorded 60.9 hours of sunshine in the month.
Given the generally murkiness of the winter, the bulk of the savings and benefits this month again come from using the Octopus Go tariff. This supplies heavily discounted (5p/kWh) electricity between 00:30 and 04:30, which we use to pour dirt cheap electrons into the 14 kWh Tesla Powerwall domestic storage battery + 100 kWh Tesla Model X and 30 kWh Nissan Lead + (new this month) 1 kWh Riese & Müller eBike.
In overview, December 2019 produced £502.45 in financial savings and benefits. And 796 kg of CO2 emissions avoided. The detailed monthly performance report can be downloaded by clicking the image at the end of this page.
The detailed monthly report can be downloaded by clicking on the image at the bottom of this page. Before that, here’s the link to Octopus Energy if you’d like to get your hands, or (more accurately) your meter, on to all that lovely super-cheap electricity.
November was another very dull month with little consistent sunshine until the last two days. When the Met Office publish the sunshine hours stats, we’ll update this post with that information. But it wouldn’t be a massive surprise if this turned out to be one of the dullest November in North East England.
With the lack of sunshine in mind, only just over 100 kWh of solar energy was generated, so most of our savings this month came from the Octopus Go super-cheap off-peak electricity we charged into the combine 144 kWh batteries of the Tesla Model X, the Nissan Leaf and the Tesla Powerwall domestic energy storage. As usual, the petrol we didn’t have to buy to cover the mileage we drove in the EVs was a major contribution.
In headline summary, the headline performance result in November 2019 was a saving of £506, and 759 kg of CO2 emissions avoided. the detailed monthly performance report can be downloaded by clicking the image at the end of this page. The key numbers were as follows.
£228 cost of electricity savings versus UK average cost on total consumption of 2,252 kWh.
£278 saved versus cost of petrol, to cover the 1,756 miles we charged to our cars using 100% renewably-generated electricity.
405 kg CO2 emissions avoided by using 100% renewably-generated electricity.
354 kg CO2 emissions avoided by charging 1,756 miles of motoring using 100% renewably-generated electricity.
Also as usual, here are the referral links to Octopus Energy and Tesla if you want to start making these kind of savings yourself. See the links page for details about how the referral links work and the benefits both you and we receive.