Solar Powered EV Charging

Grey_Critic

A friend of mine charges hi from Solar Panels.

Petriix

I used to charge from solar. Over a year I managed to put about 1MWh in from the sun while another 2MWh came from the grid. I stopped solar charging altogether when I switched to metered exports at 15p per kWh as it became a net loss vs charging overnight for 7p a unit. 

born_again

QrizB said:

Everyone over in the Energy forum (or Green & Ethical) will point out that, if you don't connect your solar panels to the grid, you'll be missing out on the benefit of export payments. Meanwhile by not connecting your car charger to the grid you'll be missing out on preferential EV tariffs.

By all means put solar panels on your roof - as many as will fit, or as many as you can afford if fewer - but connect them and your EV charger to the mains.

I can give you some illustrations of costs and savings if you really want.

Related, will the Motability scheme contribute towards the cost of the EV charger?

They pay for a standard install. 

QrizB

born_again said:

QrizB said:

Everyone over in the Energy forum (or Green & Ethical) will point out that, if you don't connect your solar panels to the grid, you'll be missing out on the benefit of export payments. Meanwhile by not connecting your car charger to the grid you'll be missing out on preferential EV tariffs.

By all means put solar panels on your roof - as many as will fit, or as many as you can afford if fewer - but connect them and your EV charger to the mains.

I can give you some illustrations of costs and savings if you really want.

Related, will the Motability scheme contribute towards the cost of the EV charger?

They pay for a standard install. 

OK, so OP can probably get the charger installed in/at his garage FOC? The only question is whether it'll need a trench for a buried cable, or not?

Edit to add: Also, if the garage roof is the best/only place for solar panels, with a bit of planning it should be possible to run the solar generation cable in the same trench (if one is required) and share the costs there.

Seems a no brainer?

born_again

QrizB said:

born_again said:

QrizB said:

Everyone over in the Energy forum (or Green & Ethical) will point out that, if you don't connect your solar panels to the grid, you'll be missing out on the benefit of export payments. Meanwhile by not connecting your car charger to the grid you'll be missing out on preferential EV tariffs.

By all means put solar panels on your roof - as many as will fit, or as many as you can afford if fewer - but connect them and your EV charger to the mains.

I can give you some illustrations of costs and savings if you really want.

Related, will the Motability scheme contribute towards the cost of the EV charger?

They pay for a standard install. 

OK, so OP can probably get the charger installed in/at his garage FOC? The only question is whether it'll need a trench for a buried cable, or not?

Edit to add: Also, if the garage roof is the best/only place for solar panels, with a bit of planning it should be possible to run the solar generation cable in the same trench (if one is required) and share the costs there.

Seems a no brainer?

They could. But why use solar to charge car, when you can export solar for 15p & charge car for 7p with Octopus 🤷‍♀️ 

QrizB

born_again said:

QrizB said:

born_again said:

QrizB said:

Everyone over in the Energy forum (or Green & Ethical) will point out that, if you don't connect your solar panels to the grid, you'll be missing out on the benefit of export payments. Meanwhile by not connecting your car charger to the grid you'll be missing out on preferential EV tariffs.

By all means put solar panels on your roof - as many as will fit, or as many as you can afford if fewer - but connect them and your EV charger to the mains.

I can give you some illustrations of costs and savings if you really want.

Related, will the Motability scheme contribute towards the cost of the EV charger?

They pay for a standard install. 

OK, so OP can probably get the charger installed in/at his garage FOC? The only question is whether it'll need a trench for a buried cable, or not?

Edit to add: Also, if the garage roof is the best/only place for solar panels, with a bit of planning it should be possible to run the solar generation cable in the same trench (if one is required) and share the costs there.

Seems a no brainer?

They could. But why use solar to charge car, when you can export solar for 15p & charge car for 7p with Octopus 🤷‍♀️ 

Yes, agreed.

Sorry, does it read as though I've suggested otherwise?

MX5huggy

A Solar PV system to charge your car doesn’t make any sense financially. £4000 spent on it would alternatively get you 48000 miles of grid electricity at standard rate (25p per kWh, car efficiency of 3 miles per kWh). 

Additionally you can only charge a car with 1.4kW or more of electricity so when solar production is low you don’t have enough to charge the car at all. Yesterday my 4kWp system produced 6.4 kWh but at no point was it producing 1.4kW or more so it would not have put anything into the car even if it was there to charge. 

That is not to say EV’s and PV  batteries are not great solutions I would encourage getting all 3 but having a PV to exclusively charge the car is not practical or financially viable. 

QrizB

Ok, we're going to talk numbers. Let's do this 😈

Current situation:

Let's assume you're using 2500kWh/yr at 25p/kWh with a £200/yr standing charge.

2500 x 0.25 + 200 = £825/yr.

Let's also assume you're running a combustion-engined car for 6000 miles/yr at a fuel cost of 15p/mile (about 40-45mpg).

6000 x 0.15 = £900/yr.

That's a total of £1725/yr.

Repace car with EV:

Domestic electricity cost is uncanged at £825/yr.

Car fuel cost changes to 6000 miles at 3 miles/kWh = 2000 kWh at 25p/kWh

2000 x 0.25 = £500/yr

Total cost £1325/yr, a saving of £400/yr.

Switch to EV tariff:

I'm going to use Intelligent Octopus Go as my example; 7p/kWh for 6 hours overnight and 29p/kWh at other times.

Domestic electricity cost: say 400kWh/yr at 7p/kWh plus 2100kWh/yr at 29p/kWh, plus SC.

400 x 0.07 + 2100 x 0.29 + 200 = £837/yr (a £12/yr increase).

EV charging: 2000 kWh/yr at 7p/kWh.

2000 x 0.07 = £140/yr

Total cost £977/yr, a further saving of £348/yr.

Add grid-tied solar PV (to garage roof or elsewhere):

Assume you take one of the recent quotes from the G&E forum and can fit 6kWp of solar PV for £5500. On a south-facing roof in England you'll probably generate 5500-6000 kWh/yr. Split east/west like the OP's garage you'll make a bit less. I'm going to assume 5000kWh/yr as it makes the sums easier.

For your domestic energy, you might be able to replace 1000kWh/yr with "free" solar PV (the other 4000kWh/yr being exported). So you're now using 400kWh/yr at 7p/kWh plus 1100kWh/yr at 29p/kWh, plus SC.

400 x 0.07 + 1100 x 0.29 + 200 = £547/yr (£290/yr saving)

You're charging your car in the middle of the night we electricity is cheap, so that's unchanged.

EV charging: 2000 kWh/yr at 7p/kWh.

2000 x 0.07 = £140/yr

Solar export: I'm going to use Outgoing Octopus Fixed as my export tariff example, paying 15p/kWh.

You're exporting 4000kWh/yr at 15p/kWh.

4000 x 0.15 = £600/yr
Total electricity cost is now 547 + 140 - 600 = £87/yr, a "solar saving" of £890/yr and a payback period (assuming no tariff changes) of 5500 / 890 = 6.2 years.

born_again

QrizB said:

Switch to EV tariff:

I'm going to use Intelligent Octopus Go as my example; 7p/kWh for 6 hours overnight and 29p/kWh at other times.

Domestic electricity cost: say 400kWh/yr at 7p/kWh plus 2100kWh/yr at 29p/kWh, plus SC.

400 x 0.07 + 2100 x 0.29 + 200 = £837/yr (a £12/yr increase).

EV charging: 2000 kWh/yr at 7p/kWh.

2000 x 0.07 = £140/yr

Total cost £977/yr, a further saving of £348/yr.

Nice base line figure
Bonus on IOG is that the tariff also gives charging at peak times at off peak rate, which also includes whole house usage.
I have OHME charger & this now has been limited to 2 ready by times. 11:00 & 04:00 on IOG. Setting to 11:00 gives you daytime charges at 7p. Yet to be refused, & many go to much later, with odd interruption due to grid load, when the required % can not be delivered by the required time. 
My average unit cost over  the last 18 months is between 11 & 15p kWh depending on how much our 2 cars require charging.

QrizB

A year has passed and I know the OP is still thinking about solar PV, so here's an updated set of numbers.

Current situation:

Electricity prices are essentially unchanged.

If you're using 2500kWh/yr at 25p/kWh with a £200/yr standing charge.

2500 x 0.25 + 200 = £825/yr.

Fuel prices are up.

Let's also assume you're running a combustion-engined car for 6000 miles/yr at a fuel cost of 17p/mile (about 40mpg for a petrol, 50mpg for a diesel).

6000 x 0.17 = £1020/yr.

That's a total of £1845/yr.

Repace car with EV:

Domestic electricity cost is unchanged at £825/yr.

Car fuel cost changes to 6000 miles at 3 miles/kWh = 2000 kWh at 25p/kWh

2000 x 0.25 = £500/yr

Total cost £1325/yr, a saving of £520/yr.

Switch to EV tariff:

Intelligent Octopus Go is currently slightly more expensive than 2025.

8p/kWh for 6 hours overnight and 33p/kWh at other times.

Domestic electricity cost: say 400kWh/yr at 8p/kWh plus 2100kWh/yr at 33p/kWh, plus SC.

400 x 0.08 + 2100 x 0.33 + 200 = £925/yr (a £100/yr increase).

EV charging: 2000 kWh/yr at 8p/kWh.

2000 x 0.078= £160/yr

Total cost £1085/yr, a further saving of £240/yr.

Add grid-tied solar PV (to garage roof or elsewhere):

Solar PV is a little more expensive than in 2025.

Per this recent quote on the G&E forum you can fit 5.15kWp of solar PV for £5500. On a south-facing roof in England you'll probably generate 5000 kWh/yr. Split east/west like the OP's garage you'll make a bit less. I'm going to assume 4500kWh/yr as it makes the sums easier.

For your domestic energy, you might be able to replace 1000kWh/yr with "free" solar PV (the other 3500kWh/yr being exported). So you're now using 400kWh/yr at 8p/kWh plus 1100kWh/yr at 33p/kWh, plus SC.

400 x 0.08 + 1100 x 0.33 + 200 = £595/yr (£330/yr saving)

You're charging your car in the middle of the night when electricity is cheap, so that's unchanged.

EV charging: 2000 kWh/yr at 8p/kWh.

2000 x 0.08 = £160/yr

Solar export: Outgoing Octopus Fixed has dropped since last year, now paying 12p/kWh.

You're exporting 3500kWh/yr at 12p/kWh.

3500 x 0.12 = £420/yr

Total cost is now 595 + 160 - 420 = £335/yr, a "solar saving" of £750/yr and a payback period (assuming no tariff changes) of 5500 / 750 = 7.3 years.

Add a battery:

OP is talking in other threads of adding a battery with a "home gateway" function to allow off-grid use. One way to achieve this would be to fit a Tesla Powerwall with their gateway. Note that I think OP uses too little electricity to justify a battery on economic grounds, but if they want grid-independence the extra cost is inevitable.

This recent G&E quote was £11k including 5.2kWp of solar PV (prices might've risen a bit since it all kicked off in the Gulf).

The PW3 will let the OP buy all their imported electricity at 8p/kWh, rather than paying 33p/kWh for some of it.

1500 x 0.08 + 200 = £320/yr (£275/yr saving)

You're still charging your car off-peak at 8p/kWh

2000 x 0.08 = £160/yr (no change)

With the extra PV, you're now exporting an additional 1000kWh/yr.

4500 x 0.12 = £540 (extra £120 earnings)

Total cost is now 320 + 160 - 480 = zero, with a "battery saving" of £335 a year and a payback period of 5500 / 335 = 16.4 years.

As expected, the PW3 doesn't make economic sense for a low user but it does bring a degree of grid-independence if you're concerned about electrical blackouts.