Annual Performance Report

So we’ve finally got a full 12 months of data. And we’re very pleased with the results.

Around £5,000 in financial savings.

Over 6 tonnes CO2 emissions avoided.

Over 16,000 miles range charged into our electric cars at home.

Click the image below for the full report, available to view or download as a PDF (16MB)

Annual Performance Summary

If you wish to indulge your inner ElectroGeek, you may be interested in the fully detailed month by month performance reports. We have published this level of detail roughly every month on these blog pages. We have now collated the information into a single PDF, which is available to view or download here. Beware, it’s a large file (c. 55MB) so it may take some time to appear.

September 2020 Performance Report

Finally reached Month 12 of detailed data collection. So now we’ve got a full year’s worth of information on:

  • Consumption: total kWh slurped down by the house and Anne’s electron-munching pottery kiln.
  • Consumption: total kWh ‘fuelled’ into the two EVs.
  • Self-generation: total kWh generated by the 7.5 kWp solar panel installation on the roof.
  • Grid imports: total kWh imported from National Grid, using the 100% renewable Octopus Go smart tariff which provides dirt cheap electricity between 00:30 and 04:30 every night and a slightly below-average cost at all other times.
  • Storage input: total kWh charged into the domestic storage battery, using a mix of only solar generation and off-peak grid electricity.
  • Storage output: total kWh discharged from the domestic storage battery at peak times, avoiding grid imports.
  • Total financial savings from smart electricity generation, storage and discharge over the year’s domestic and pottery kiln consumption.
  • Total mileage charged into EVs, using solar and off-peak electricity.
  • Total financial savings from use of EVs charged on this electricity mix, versus the cost of petrol which would have been required to cover the same mileage in Internal Combustion Engine (ICE) cars.
  • Total tonnes emissions avoided from domestic energy optimisation.
  • Total tonnes emissions avoided by EV use.

You can see or download a PDF summary of the whole year’s data (14MB) by clicking the image below.

Annual Performance Report

Below is the final performance report for the data collection year, September 2020.

It was not a bad month weather-wise, with the Met Office reporting a decent 151 hours of sunshine in our area. The key results are tabulated below.

ItemResult
Solar production524 kWh
Off-peak grid energy imported725 kWh
Peak grid energy imported169 kWh
Peak grid imports avoided by using stored energy from Powerwall battery484 kWh
Total energy consumed (domestic consumption and EV charging)1,418 kWh
Net cost of grid energy, incl standing charge, net of Govt payments for solar£39.88
Cost of 1,162 kWh at UK ‘Big 6’ average rate per kWh£219.75
Saving on 1,162.6 kWh vs UK Big 6 average rate£179.87
Total range charged to EVs, from solar and off-peak grid imports1,194 miles
Actual cost of solar + off-peak grid energy to charge 1,185 miles£15.14
Fuel costs to drive an ICE car 1,185 miles using @35mpg & £1.32/litre£252.55
Saving on 1,185 miles vs cost of motor fuel for same mileage£237.41
Electricity and motor fuel savings in month£417.28
CO2 savings on domestic energy by using solar & 100% renewable grid energy255.2 kg
CO2 savings on 1,185 emissions-free miles versus ICE @ 125.1 g/km240.4 kg
Total CO2 emissions avoided in month495.6 kg
September 2020 Performance Data

The usual monthly calcographic is available for download here or by clicking the image below.

September 2020 Calcographic

August 2020 Performance Report

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.

ItemResult
Solar production564 kWh
Off-peak grid energy imported509 kWh
Peak grid energy imported89 kWh
Peak grid imports avoided by using stored energy from Powerwall battery423 kWh
Total energy consumed (domestic consumption and EV charging)1,162 kWh
Net cost of grid energy, incl standing charge, net of Govt payments for solar£17.26
Cost of 1,162 kWh at UK ‘Big 6’ average rate per kWh£180.21
Saving on 1,162.6 kWh vs UK Big 6 average rate£162.95
Total range charged to EVs, from solar and off-peak grid imports1,185 miles
Actual cost of solar + off-peak grid energy to charge 1,185 miles£13.65
Fuel costs to drive an ICE car 1,185 miles using @35mpg & £1.32/litre£248.97
Saving on 1,185 miles vs cost of motor fuel for same mileage£235.07
Electricity and motor fuel savings in month£398.02
CO2 savings on domestic energy by using solar & 100% renewable grid energy209.3 kg
CO2 savings on 1,185 emissions-free miles versus ICE @ 125.1 g/km238.7 kg
Total CO2 emissions avoided in month448.0 kg
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 2020 Performance Report

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 negative net 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.

July 2020 energy input blend and usage

Here comes the sun, here comes the sun, and I say it’s alright…(June 2020)

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.

Covid 19 : Carbon Dioxide Nil (May 2020)

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.  

So, there you have it; a brilliant result!

Covid 19 : Carbon Dioxide 0

Great sunshine, shame about the virus. (April 2020)

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.

River North Tyne, near Wark
eBike on 14th Century byway in Northumberland

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.

Key results:

  • 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 this global 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.

Tesla preparing Vehicle To Grid bidirectional charging and registering as a UK Generator. What does it all mean?

Some really important news broke in mid-May 2020.

Tesla is apparently enabling Vehicle To Grid (V2G) charging capabilities on its vehicles. 

V2G is super-important.  This basically completes the jigsaw which enables Tesla to become a major player as a wholesale participant in energy markets by leveraging:

a) its fleet of stationary batteries, Powerwall and Powerpacks;

b) its fleet of mobile batteries, in owners’ cars;

c) its fleet of solar installed on owners’ roof spaces;

d) Tesla’s Autobidder platform to enable grid market participation; and

e) the company’s Edge Computing capability to enable it to route electricity intelligently (and profitably) between solar generation, stationary batteries, any V2G-equipped Tesla car and superchargers.

The addition of V2G is a game-changer, in that it allows Tesla to use the entire fleet of cars and Powerwalls in a given country to offer (highly lucrative) grid services such as peak shifting, demand spike mitigation, and Rate Of Change Of Frequency (ROCOF) response.  Some of these grid services require response within seconds, which only battery storage, some pumped storage hydro, and Compressed Air Energy Storage (CAES) can deliver.

In countries with a functional dynamic electricity market and an increasing proportion of generation coming from (inherently intermittent) renewables, any wholesale player who is able to offer near-instant-response storage on a significant scale is in a very strong position.  And Governments/Grid Operators love it too, because the combination of renewables plus large scale storage enables a massively faster transition to net zero carbon.

So I’d expect Tesla to be using its unique app-enabled access to a highly distributed fleet of huge numbers of (relatively small) batteries and, in lesser number, domestic-scale solar installations to aggregate this distributed storage and micro-generation capacity up to the industrial scale which enables it to play in the wholesale electricity market.  

At the wholesale scale, it will then use Autobidder to dynamically route the surpluses it has aggregated to wherever it will make the most money.

The UK is probably the most advanced dynamic-priced electricity market in the world.  So it’s no surprise that Tesla recently lodged its formal application with the regulator to operate as a generator supplying the UK grid.  

This will not be about Tesla building a large fixed-plant power station.  Instead this will involve:

  1. Tesla dynamically supplying the grid from the distributed storage, into which its IOT platform gives it access and insight, to make money from the lucrative peak-mitigation and ROCOF services the grid requires;
  2. plus using the trading rights a grid-connected generator enjoys to purchase energy at low-cost (or even negative cost) super off peak periods when the grid has a surplus; and
  3. pump that super-cheap energy to its customers’ cars and Powerwalls so that those end users home and cars are optimally charged, at the cheapest possible rate, with enough energy to power each user’s intelligently-predicted home load or next car trip.

Of course, I’m expecting Tesla’s algorithms, using the company’s fleet-wide data and predictive analytics, to be able to make all the necessary choices, in real time.  I’m also expecting that there will be zero requirement for the individual end customer to make any input.  Apart, perhaps, from telling ‘the system’ via the Tesla App that she/he wants to go to a specific destination tomorrow morning (when that’s different from a regular commute pattern, which Tesla already knows about anyway).  In that case, I’d expect the battery to be optimally charged overnight to reach the desired destination, taking into account time-optimised supercharger stops where necessary. 

So what’s the killer advantage from Tesla’s POV as a grid-connected generator with wholesale trading rights?  It’s all about capital cost. 

A.N. Other generator would have to stump up the cash to build or buy the power station before they can sell the electricity it producers.  In Tesla’s case, it’s their customers who have paid the capital cost of ‘building the power station’, because they paid Tesla when they took ownership of their car or Powerwall.  The difference of course is that, whilst each Tesla customer owns only a tiny fraction of the overall capacity, collectively they own 100% of it. This shifts 100% of the risk off Tesla’s accounts.

Things are moving pretty rapidly.  Tesla have already quietly partnered with, Octopus, probably the UK’s most innovative domestic electricity supplier, to offer the “Tesla Energy Plan”.  This is marketed as “an energy tariff specifically designed for Tesla vehicle owners who have solar panels and Powerwall installed in their home.”  Note the solar panels bit.  This is important, because anybody with a solar inverter is already technically enabled and legally allowed to export surplus energy to the grid.

Clearly, there has to be a compelling answer to the question from the customer’s perspective: ‘what’s in it for me?’  And that’s as follows.  

  • In the UK, typical average domestic electricity costs 15p/kWh.  
  • Under the Octopus Tesla Energy Plan you pay only 8p/kWh for the energy you buy from the grid.
  • And, super-importantly, you also get paid 8p/kWh for any energy Tesla export to the grid on your behalf.  

The Octopus/Tesla collaboration also clearly shows the direction of travel commercially too.  “It offers customers 100% clean electricity and savings of up to 75% compared to Big 6 tariffs. This is achieved through giving you the lowest flat electricity tariffs in the UK, combined with smart management of your home’s energy and electric vehicle (EV) charging.”  

The key detail is in the FAQs.

Q: “What happens if I already have another electric vehicle charger installed, do I still need to have a Tesla Wall Connector?”

A: “No, although we do need you to disable any smart charging features if your charger has those capabilities. Doing this will allow you to use your existing charger for the Tesla Energy Plan.”

This couldn’t be clearer. 

  • As the end-user you’re being asked give up the right to route your solar generation intelligently to your Powerwall and your Tesla car. In our case, this would mean switching off the intelligent functions in the myenergi ‘zappi’ smart charger, which routes any surplus solar production into our Model X, net of domestic consumption and Powerwall charge up.  
  • In return, intelligent energy and storage management done by Tesla, on your behalf, will ‘typically save you 75%’ compared to Big 6 suppliers.

From our own perspective, it will be interesting to do the numbers at the end of a full year to find out which approach saves most money.

  • Our own plan, which is essentially as follows. Install the smart tech on-site, maximise self-consumption, make maximum use of 5p/kWh super-super-cheapo Octopus electricity in the 4 hour window between 00:30 and 04:30 every morning, and minimise use of 13p/kWh energy during other 20 hours. Try to get exports to grid as close to zero as possible.
  • Or just hand the whole process over to Tesla, pay 3p more per kWh than our super-off-peak consumption, and let Tesla pay us 8p/kWh for exporting as much of our solar generation as possible whilst still leaving us enough to drive the cars when and where we want and power the house from the Powerwall when the sun’s not shining.

Watch this space!

Elektrek broke the V2G story here.

You can sign up with Octopus Energy here. This referral link will save you, and us, £50 off an Octopus electricity bill.

March 2020 Performance Update

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.

Major UK Government incentives for EVs

At the start of the new tax year on 6 April 2020, a major uprating of UK Government tax breaks and incentives for EVs comes into force.

When employer and employee tax breaks are combined with other hard cash savings of EV ownership, the total financial benefits of owning and driving and EV for business use, compared to a old-tech car, could amount to 100% or more of the sticker price a new EV over three years and 45,000 miles of use.

Document updated 27 May 2020 to reflect the elimination of the “luxury supplement” of £320 Road Tax from Year 2 onwards, but only for all battery electric vehicles. More expensive ICE cars still have this penalty.

The full report is is here.

Thanks to CleanTechnica for featuring this report. Link here.