How much does your electric car add to your electricity bill?

[The Lad]

I guess it will be a rapid of some sort, 7 kw will take several hours to give a reasonable mileage at around 30 miles per hour. Good to top up if you have declined to participate in retail therapy though.

 

[NoRoute]

First, that public charging points have a failure mode whereby they refuse to release the mechanical lock on the charging cable, thus leaving the vehicle attached until the operator of the charging point fixes the problem.

Not heard of that, type 2 (slow and fast chargers) the cable gets locked at both ends and the EV controls the lock at the EV end so should always be possible to release to the cable to detach the vehicle. Normally this triggers the charge point to unlock at it's end.

There have been occasional reports of charge points where the locking mechanism did not release, so while the vehicle can release it at it's end, the cable is retained and needed tying up and retrieving later.

 

[david1212]

With the domestic standard price per kWh to be 28p from April I wonder how dual-rate tariffs will change?
The new rate is still below the current wholesale cost. Unless this is reversed the domestic rate will be increased again in 6 months time. Even if there is a fall so directly a surplus first the 'overdraft' from the wholesale price being above the retail price has to be repaid.

At the new standard rate for an EV achieving 3 miles / kWh the energy cost will be close to 10p/mile and if 2mile / kWh 14p/mile. The latter is comparable with a petrol or diesel engined car. which includes duty and a higher VAT rate as being discussed on this thread.

 

[37424]

With the domestic standard price per kWh to be 28p from April I wonder how dual-rate tariffs will change?
The new rate is still below the current wholesale cost. Unless this is reversed the domestic rate will be increased again in 6 months time. Even if there is a fall so directly a surplus first the 'overdraft' from the wholesale price being above the retail price has to be repaid.

At the new standard rate for an EV achieving 3 miles / kWh the energy cost will be close to 10p/mile and if 2mile / kWh 14p/mile. The latter is comparable with a petrol or diesel engined car. which includes duty and a higher VAT rate as being discussed on this thread.

I have gone onto another fixed tariff not sure whether that was the best idea as I think the new default variable is still cheaper although predictions are it will go up again in October in which case it my fixed tariff will probably be better.

From an EV viewpoint my overnight rate goes up to 20p per KWh from 5p which is heck of an increase but still significantly cheaper than petrol or diesel by my calcs.

 

[AM9]

With the domestic standard price per kWh to be 28p from April I wonder how dual-rate tariffs will change?
The new rate is still below the current wholesale cost. Unless this is reversed the domestic rate will be increased again in 6 months time. Even if there is a fall so directly a surplus first the 'overdraft' from the wholesale price being above the retail price has to be repaid.

At the new standard rate for an EV achieving 3 miles / kWh the energy cost will be close to 10p/mile and if 2mile / kWh 14p/mile. The latter is comparable with a petrol or diesel engined car. which includes duty and a higher VAT rate as being discussed on this thread.

You might be safe as long as the Conservatives are still hanging on to government, as they are wedded to car use and have held the duty on fuel down for over 11 years. It will increase sharply soon to give a further nudge or two to those who are reluctant to go to EVs. In practice, I think that solar installations will become the norm (where possible) for EV owners.

 

[paul1609]

You might be safe as long as the Conservatives are still hanging on to government, as they are wedded to car use and have held the duty on fuel down for over 11 years. It will increase sharply soon to give a further nudge or two to those who are reluctant to go to EVs. In practice, I think that solar installations will become the norm (where possible) for EV owners.

Solar installations are pretty useless for offsetting EV costs. A 4Kwp solar system in the UK generates on average 2.5 Kwh per day in Jan, about 8 miles ignoring charging efficiencies that rises to 15Kwh in Jun about 45 miles. Of course your EV needs to be plugged in during all daylight hours!

 

[jon0844]

45 miles in a day would be fine for many, but as you say - you'd need to be plugged in when you're likely out! And only driving that much when there's plenty of daylight!

That's why I think a home battery is first on my shopping list, with solar panels added in later. I am hoping that solar panels will get cheaper still, and possibly slightly more efficient also.

 

[paul1609]

45 miles in a day would be fine for many, but as you say - you'd need to be plugged in when you're likely out! And only driving that much when there's plenty of daylight!

That's why I think a home battery is first on my shopping list, with solar panels added in later. I am hoping that solar panels will get cheaper still, and possibly slightly more efficient also.

To be honest unless you've got very unusual consumption patterns or a very big house and lots of Solar Panels Home Batteries will never recover the capital cost in savings.
On a 4Kwp solar system during the winter your 2.5 Kwh over 8 hours averages 312 watts per hour, that's easily absorbed by the background electrical consumption in the average home (central heating pump and boiler fan, fridge freezer, sky box etc) leaving nothing to charge the battery for 6 months of the year.

 

[najaB]

To be honest unless you've got very unusual consumption patterns or a very big house and lots of Solar Panels Home Batteries will never recover the capital cost in savings.

Batteries can also be used to time-shift usage of grid electricity from on to off-peak.

 

[paul1609]

Batteries can also be used to time-shift usage of grid electricity from on to off-peak.

Indeed but let's consider a real life example the difference between peak and off peak electricity is 13p per unit on economy 7. A tesla Power wall 3 has a usable capacity of 13.7 Kwh, a return trip efficency of 90%. Even if you use all of the 13.7 every day (many UK homes wouldn't in summer). It would take 10 years to recover the £10200 price of the equipment. I suspect it makes better sense in California with all year sunshine and higher consumption because of air conditioning but in the average UK home nah.

 

[najaB]

It would take 10 years to recover the £10200 price of the equipment.

Well, for one thing the Powerwall is grossly overpriced. ~13kWh of storage shouldn't cost you much over £5-6,000. I just bought 5.2kWh of LiFePo with BMS for £1,300.

 

[jon0844]

Well, for one thing the Powerwall is grossly overpriced. ~13kWh of storage shouldn't cost you much over £5-6,000. I just bought 5.2kWh of LiFePo with BMS for £1,300.

This is why I'm hesitant to invest right now, because it seems like the industry is full of scammers trying to rip consumers off (if that's a bit harsh, let me rephrase and use the words 'take advantage of'). As I haven't got the knowledge of the trustworthy businesses, or the time to fully research things, I am sitting back and waiting - hopefully - for things to become easier.

 

[paul1609]

Well, for one thing the Powerwall is grossly overpriced. ~13kWh of storage shouldn't cost you much over £5-6,000. I just bought 5.2kWh of LiFePo with BMS for £1,300.

Which on a 13p margin saves you a whopping 61p a day! So around 6 years to recover the cost of the equipment alone.

 

[jon0844]

In a way, even a small saving might still make it worthwhile - especially to avoid future power outages and help offer some more independence and security.

What isn't worthwhile is paying more, and ending up never recovering the cost.

 

[StKeverne1497]

What I don't see discussion of (regarding batteries) is usable lifespan. For most things a 6-year payback isn't too bad and even 10 years could be acceptable in some circumstances, but there are two problems with this regarding batteries. Firstly battery capacity decreases slowly over time, as anyone with a 5 year-old mobile phone, laptop or Nissan Leaf will tell you. This means that a system which is initially capable of storing (say) 13kWh could store less than 10kWh by 5 years, possibly less. This reduces your capacity for timeshifting and therefore extends the payback period.

Secondly, Lithium batteries have an effectively finite number of charge-discharge cycles - mostly to do with this reduction in capacity. A friend is very keen to buy an electric car, but can't afford new (and is reluctant to rent), but all the sensibly-priced second hand cars he has seen need new batteries, which changes the equation significantly. All the evidence points to car batteries being effectively "dead" in the 7 to 10 year window, so a 10 year payback is going to end up as a net loss, and even 6 years is of marginal benefit. A friend of said friend is considering building his own battery storage using Lead-acid traction batteries, but those things also have finite lifespans - similar technology batteries in our UPSes at work need replacing every 5 years or so.

And this ignores the likelihood - especially as more people ditch tax-raising fossil fuels for (at the moment) tax-exempt electricity - that over time electricity prices will rise while incentive schemes will reduce.

A possible upside is that if you can just about - or very nearly - make your money back before the batteries need replacing, those replacement batteries should cost less (prices are generally reducing, plus some of the "infrastructure" you had to put with your original set can be re-used) so payback for the second and subsequent sets should be slightly quicker. Then again, electronics also wear out over time, so even the controls and inverter will eventually need to be replaced.

As a different friend was opining yesterday, we're at a point with reducing incentives and still relatively high costs where most "environmentally friendly" technologies are not going to save the average homeowner any money at all. Some (heat pumps being the obvious topical example) currently cost more over their lifespan than the traditional technologies (i.e. condensing gas boilers) they replace. You need to be willing to pay a bit extra to "save the planet" in terms of reduced emissions of CO₂ This is likely to change over time, but the days of bunging half a dozen solar panels on your roof and waiting for the cheques to roll in are well and truly over.

Regarding power outages - I don't think any of the existing systems are capable of riding out power cuts without some significant electrical work in the house. For example, I believe the Tesla Powerwall 2 has an inverter capable of 5kW continuous. In order to allow this unit to run the house in the event of a power cut you would have to be able to "shed" loads - so the Powerwall could be connected to lighting circuits, the circuit which runs the boiler and heating controls and maybe one segregated sockets circuit, but it must be kept well away from electric showers (8 - 10kW), immersion heaters (typically 3kW), cookers (typical oven is 2kW, rings are 1kW, 2kW, 3kW), and you'd want to be careful with microwave ovens (2kW+), kettles (2.5 or 3kW), and those "white goods" (dishwasher, washing machine, tumble dryer) which typically have a 2kW heater as well as motors etc. Doing this means re-arranging (replacing) your consumer unit (fuseboard) and/or re-routing or re-wiring some circuits. Older installations, for example, might have the central heating system run from a general sockets circuit. It's not that you couldn't run the kettle from the Powerwall - the specs definitely imply that you could - it's more that you need to be able to guarantee that you are not running the kettle, the microwave, the dishwasher, the fridge, the lights, the TV and the computers at the point the grid goes down, so that the poor Powerwall doesn't have to try to pick up 10kW.

It's also a whole other kettle of fish regarding grid connection if you wish to ride out power cuts, in order to avoid feeding energy back into the system which is not only dangerous for your equipment but could also be dangerous for people working on the lines. In the case where your house receives an earth via the neutral connection or the cable metal sheath you have also to consider what happens if the power cut is due to a severed line. Most grid-connected systems are mandated to shut down in the event of a loss of mains, and this was a contributory factor to that massive (but very brief) power cut a couple of years ago (August 2019) which stranded all those class 700 / 717s.

I'm not saying it can't be done - I know it has been done - but it's not as simple as plugging in a battery and suddenly you are making dinner for the whole street when there's a Sunday lunchtime power cut.

M.

 

[najaB]

Secondly, Lithium batteries have an effectively finite number of charge-discharge cycles - mostly to do with this reduction in capacity.

At typical energy storage charge/discharge rates (way less than 1C) LiFePo has somewhere between 3,000 and 5,000 cycles before it hits 80% capacity. So somewhere between 8 and 15 years.

It is true that EV batteries don't last quite as long, but that's because they are worked a lot harder - accelerating away from traffic lights can draw hundreds of amps.

== Doublepost prevention - post automatically merged: 16 Feb 2022 ==

Which on a 13p margin saves you a whopping 61p a day! So around 6 years to recover the cost of the equipment alone.

That assumes that the differential between peak and off-peak is going to remain 13p/kWh, which is highly unlikely. As noted in the recent smart meter thread, some suppliers give you free electricity at certain times of the day.

 

[Annetts key]

Lead acid cells last about five to six years. Industrial users (who use them for standby power systems, including but not limited to UPS systems, vital control systems and generator starter battery systems) often replace them regardless of condition every five years or sometimes as often as every two years.

Lithium battery technology can last longer, but it depends on the number of charge/discharge cycles and how deep the discharge is.

Unless you have a manual or automatic transfer switch, any backup power / solar PV or other power generator has to automatically disconnect/shut down in the event of the loss of the incoming mains supply.

If a manual or automatic transfer switch is used, this isolates the backup power supply from the mains supply. However, as said above, you still need to ensure that it cannot feed a load that is higher than it’s rating.

Hence this makes the consumer unit and all the required switchgear more complex and hence more expensive to install.

And you may need to install your own earth rod matrix system (these days a single earth rod is not usually good enough).

 

[najaB]

Most grid-connected systems are mandated to shut down in the event of a loss of mains...

Well, to be more accurate they're mandated to not feed power back into the grid. This can be by shutting down (simplest way) but more advanced systems achieve it by having an automatic transfer switch/internal relay in the inverter.

 

[SECR263]

With range angst what is to stop you towing a trailer with a geny to trickle charge the battery as you trundle along or drive the electric motor if needed. Would stop you freezing to death on the M25 in winter when it all goes really wrong for hours on end. Has anybody predicted how you shift dozens of cars with flat batteries on a winters night after a 5 hour stoppage?

 

[najaB]

With range angst what is to stop you towing a trailer with a geny to trickle charge the battery as you trundle along or drive the electric motor if needed. Would stop you freezing to death on the M25 in winter when it all goes really wrong for hours on end.

That's basically a plug-in hybrid.

 

[AM9]

With range angst what is to stop you towing a trailer with a geny to trickle charge the battery as you trundle along or drive the electric motor if needed. Would stop you freezing to death on the M25 in winter when it all goes really wrong for hours on end. Has anybody predicted how you shift dozens of cars with flat batteries on a winters night after a 5 hour stoppage?

A generator big enough to charge an EV's battery, a trailer and it's own weight would be quite large. It would also be illegal as the vehicle would be registered as an EV and then wouldn't comply with emission requirements, - nor would it be approved in that configuation for use on the public highway, so in other words, there's lots to stop you.
As far as '5 hour stoppages', how often are you assuming that they occur? Also, whatever that number of stoppages, how many are as a result of drivers ignoring warnings of poor weather or other likely problems?

 

[Harpers Tate]

Has anybody predicted how you shift dozens of cars with flat batteries on a winters night after a 5 hour stoppage?

The heater in my car (an air source heatpump) uses less than 0.5 kw once the car is warm and the electronics, next to nothing. Nothing else of significance being used when stopped. On that basis a 5 hour delay would require just 2.5kWh of battery power. Compare to the capacity (if full, which it clearly won't be) which in my case is 38kWh. Or, if it were almost full (say, 30kWh) it would keep me warm for ~60 hours.

 

[skyhigh]

With range angst what is to stop you towing a trailer with a geny to trickle charge the battery as you trundle along or drive the electric motor if needed. Would stop you freezing to death on the M25 in winter when it all goes really wrong for hours on end. Has anybody predicted how you shift dozens of cars with flat batteries on a winters night after a 5 hour stoppage?

Sitting for 5 hours with the heating running would use barely any battery. You certainly wouldn't have dozens of cars with flat batteries.

(And recovery services are now starting to carry batteries that can be used to charge cars that have run out)

 

[paul1609]

With range angst what is to stop you towing a trailer with a geny to trickle charge the battery as you trundle along or drive the electric motor if needed. Would stop you freezing to death on the M25 in winter when it all goes really wrong for hours on end. Has anybody predicted how you shift dozens of cars with flat batteries on a winters night after a 5 hour stoppage?

On you tube there is a track test by Carwow of a Skoda EV towing a 880 kg caravan it had a manufacturers range of 300 miles, towing the caravan at 60 mph it managed 65. I don't think any of the current EVs certainly at the lower end of market can practically tow a trailer of any size.

 

[AM9]

On you tube there is a track test by Carwow of a Skoda EV towing a 880 kg caravan it had a manufacturers range of 300 miles, towing the caravan at 60 mph it managed 65. I don't think any of the current EVs certainly at the lower end of market can practically tow a trailer of any size.

On that basis, such a car trailer combination would have far more available battery capacity than solo vehicles to provide heating and lighting in the extremely rare event of a total traffic standstill, - neither greater the weight or aerodynamic load doesn't apply when parked on a motorway.

 

[paul1609]

On that basis, such a car trailer combination would have far more available battery capacity than solo vehicles to provide heating and lighting in the extremely rare event of a total traffic standstill, - neither greater the weight or aerodynamic load doesn't apply when parked on a motorway.

Don't most EVs have an interlock which disables driving whilst plugged in to avoid incidents driving away from charging points?

 

[AM9]

Don't most EVs have an interlock which disables driving whilst plugged in to avoid incidents driving away from charging points?

I don't understand your comment/question?

 

[paul1609]

I don't understand your comment/question?

So in the context of the trailer with the generator in you can only charge whilst stationary.

 

[Ediswan]

There are now posts mixing up two different types of trailers. (1) Trailers with a generator. (2) Caravans, which drastically reduce range.

 

[paul1609]

I think that maybe there is a lack of understanding of the size of generator you're going to need to charge an EV. You could do 10A trickle charging with a small generator that you could fit in the boot of the car. Anything faster and you're going to need a generator with a 63A output socket. Something like a Hyaundi 10 KW set, that weighs circa 300kgs and is 1.2 metres high, put that in a trailer and it isn't going to be much different to towing a caravan.