Just got solar panels.

[Regulo]

There is a thread or two somewhere on here re charging using pv and there are plenty of technical experts on the forum who can discuss (somewhere else rather than hijacking this thread perhaps!).

Hi, all,
I've had solar panels for a month now, and on a sunny day, I'm seeing a peak of 1.4 kW generating (I'm not ideally situated). Considering the time of year, do the experts (that means you) think I'll be able to charge my PHEV for free in the summer, using the supplied charger? I'm home most days, so I could stick it on whenever the sun shines. If not, is there any way of reducing the charging current, even if it means extending the time taken to charge?

 

[bdbdbd]

How big is your system? I have a 4kW system (16 panels). At this time of year I get about 1kW or so. From Feb to November I expect to get more, often around 3 to 3.5kW.

The supplied charger uses around 2.2kW so the panels easily provide enough power to give free charging.

 

[steve2001]

I had a 4kW system installed in Dec just after the PHEV arrived. I am currently getting max 1.9kW in full sun around midday and this should get better as the days lengthen in the UK. On cloudy days it is much less though - cue comments about the British weather! I have a Rolec chargepoint that pulls about 3.5kW so I have found myself wondering about reverting to the lower rated plug-in 13A charge unit. But the tethered Rolec is so easy and I cannot always charge during the day due to work commitments. Would be nice to get 100% charge from the sun for free but I am happy getting what I can. It is more important to have a full battery at start of the day so I am still charging overnight quite often and topping up if I'm at home during the day.

 

[Regulo]

Mine is a 4kW system, but I could only get half on the SW facing roof, the other half are on the NE facing roof. Best daily generation so far has been 5.5 kW, so obviously nowhere near enough to charge up the car. I'm hoping to get a lot more in the summer, but I don't think it'll be enough to take care of the 2½ kW the charger takes. Still, the way I see it, every kW from the roof is a kW I don't have to buy off the grid - and they're paying me for it!

 

[Goldfinger]

We've just had a quote last night for solar panels. We can only fit 6 on the roof due to shape and having a window bang in the middle for the loft room.

So... We may not get enough power to charge the outlander outright from the panels but does this make (any ) sense...??

We get the panels....

We're both out all day at work so the panels should be 'earning'.

Come home, and charge the car from the grid, so then we're 'charged £££'.

Do it again and again that way, so would our cost of charging be free, or minimal that way??

Also, after reading the Economy 7 thread, is that another way of reducing the charging cost??

 

[rtw]

Contrary to popular notion, most solar PV installations don't push electricity back into the grid and so won't turn back the meter. You'll get paid a generation tariff plus an export tariff for the kWh your panels produce.

So with some rough figures of generation tariff around 14p per kWh, export tariff 5p per kWh and price you pay for a kWh from your supplier of 10p. And let's say the panels produce 2kW for 8 hours.

Charging the car at night:

Generated 16kWh which gains you 16 x 19p = +£3.04
Car charging 11kWh which costs you 11 x 10p = -£1.10

Charging the car whilst the sun shines:

Generated 16kWh which gains you 16 x 19p = +£3.04
Car now only takes 3kW - 2kW = 1kW over 5 hours (assuming you'll use the 13A charging lead)
Car charging 5kWh which costs you 5 x 10p = -£0.50

So basically charging whilst the panels are generating nets you more income. It's not a simple case of what you generate in the day offsetting what you use at night.

However, with the figures above as long as your panels produce 6kWh+ during the day, the generation income will offset the charge cost ... it's just not the most efficient way.

 

[Goldfinger]

On the quotation sheet it says...

Number of panels, 6

Panel output, 250watts

Orientation, 10 degrees from south

Pitch / inclination 35 degrees

Total 1350kwh per year.

What we'll be paid is...

13.88p SAP x FIT rate

Export income 47.7p

Electricity saving, 50% SAP: x Elec cost 15.9p

And, we pay 13.26p kwh to BG with a 26p daily standing charge. We're looking into changing supplier to get that lower too.



So does this help with them figures?? :?

 

[rtw]

The figures are irrelevent really. I was just demonstrating that since the electricity produced by the solar panels doesn't turn back your meter during the daytime it won't directly offset the electricity used for charging. Therefore to be most efficient you have to actually use the electricity at the time it is generated.

However, the income you get from the generation/export tariff on sunny days will almost certainly offset the cost of charging at night. It depends on how you think about it since you still have to factor in your normal usage + the cost of the panels.

 

[anko]

Contrary to popular notion, most solar PV installations don't push electricity back into the grid and so won't turn back the meter.

When it is not pushed back into the net and you do not use it yourself, then what happens to the electricity generated by the PV installation?

In a common household situation in the Netherlands, for what you push back, they will pay you the same kWh rate as they charge you for what you get from them. At least up to the amount of electricity you obtain from the grid. Effectively you pay for "kWh in" - "kWh out". Without that, it would be very difficult to (financially) profit from a PV installation.

 

[Goldfinger]

Just been doing a bit digging with regard to our utility bills..

At least we know Economy 7 or 10 won't work / be worth it.... :roll:

 

[rtw]

Contrary to popular notion, most solar PV installations don't push electricity back into the grid and so won't turn back the meter.

When it is not pushed back into the net and you do not use it yourself, then what happens to the electricity generated by the PV installation?

In a common household situation in the Netherlands, for what you push back, they will pay you the same kWh rate as they charge you for what you get from them. At least up to the amount of electricity you obtain from the grid. Effectively you pay for "kWh in" - "kWh out". Without that, it would be very difficult to (financially) profit from a PV installation.

The profit comes from the generation tariff which is a fixed 14p per kWh regardless of whether you use the energy or not.

Any surplus energy feeds the local power network, ie. your neighbours, but this 'exported' energy cannot be measured because most domestic meters in the UK are not capable running backwards. That would require a new smart meter which bizarrely aren't installed with a new PV installation.

So instead you're given just under 5p on top of the generation tariff for 50% of the kWh the solar panels generate as a guesstimate of what might've been exported.

Therefore the more solar energy you consume yourself the more cost efficient the installation is as you are NOT buying electricity at 10p per kWh, as opposed to selling it back at a measly 2.5p per kWh. (The 14p per kWh doesn't count for comparison because you get that either way).

@Goldfinger, why did you come to the conclusion that Economy 7 isn't worth it? That's what I'm using and I can't see why it's not cheaper to charge when the rate is lower.

 

[Goldfinger]

Not sure, but after reading the MSE's web pages, we were hoping the E7 tariff kicked in earlier. But at midnight??

How would we go about switching the charger on at that time? Unless we put the 3 pin charger on a timer??

But what about the other type of charger you get installed - how would you put that on a timer??

Confused now.... :?

 

[BeeJay]

Not sure, but after reading the MSE's web pages, we were hoping the E7 tariff kicked in earlier. But at midnight??

How would we go about switching the charger on at that time? Unless we put the 3 pin charger on a timer??

But what about the other type of charger you get installed - how would you put that on a timer??

Confused now.... :?

The car itself has its own timer.

 

[Hypermiler]

Goldfinger

You can get 300w panels now if space is short - not sure whether extra cost is worth it. To be honest, not sure whether 6 panels is going to make much difference altho your orientation is good. What is the return/payback period on your investment? Usually you want as close to the FIT rate change as possible - i.e. 4kwp or 10kwp.
Cheers
H

 

[rtw]

How would we go about switching the charger on at that time? Unless we put the 3 pin charger on a timer?

Yes, 3 pin charger on a timer, or set the car's timer (GX4 only).

I have a GX3h and a charging point, but I'm pretty much always still up after midnight, so I just plug in before bed.

I'm sure there would be a solution to putting a charging point on a timer though. Presumably a hardwired timer on that circuit would suffice. But actually, if you use the 3 pin charger for night time, since it doesn't matter if it takes 5 hours, and the charging point for faster topups as required during the day, then a timer on the charging point would be unnecessary.

But then again, since this is a thread about solar panels, you should really be using the 3 pin charger during the daytime too in order to use as much of the solar energy as possible.

It all comes down to personal preference though. It's very easy to get wound up about conserving every last drop of energy at the expense of inconvenience and stress. Do the sums and if it turns out you're only saving pennies, is it really worth the effort?

 

[maby]

...
@Goldfinger, why did you come to the conclusion that Economy 7 isn't worth it? That's what I'm using and I can't see why it's not cheaper to charge when the rate is lower.

Surely the point about Economy 7 is that while the night time rate is cheap, the daytime rate is usually more expensive than a standard tariff - you do need to consume quite a lot more electricity at night than you do in the day for the sums to come out in your favour. When we bought the Outlander, I did the sums based on our anticipated pattern of usage and the E7 tariffs that were published - I came to the conclusion that we might save a small amount overall, but not enough to be worth the hassle of switching and it would not have required me to do many charges during the daytime to actually leave me worse off.

 

[Ozukus]

...
@Goldfinger, why did you come to the conclusion that Economy 7 isn't worth it? That's what I'm using and I can't see why it's not cheaper to charge when the rate is lower.

Surely the point about Economy 7 is that while the night time rate is cheap, the daytime rate is usually more expensive than a standard tariff - you do need to consume quite a lot more electricity at night than you do in the day for the sums to come out in your favour. When we bought the Outlander, I did the sums based on our anticipated pattern of usage and the E7 tariffs that were published - I came to the conclusion that we might save a small amount overall, but not enough to be worth the hassle of switching and it would not have required me to do many charges during the daytime to actually leave me worse off.

I did similar calculations, and as I work from home a lot, I worked out that I'd be £20 off worse per month. I think the only people that really benefit from this nowadays are people with Storage Heaters as all modern white goods are so efficient, and the things that are high consumers now need to be on during your daytime hours. Plus the number of consuming devices like PC's, laptops, tablets, mobile phones, handsfree phones, TVs in multiple rooms, etc, means that the number of daytime consuming units is far higher than what it was 10 years ago.

 

[greendwarf]

...
@Goldfinger, why did you come to the conclusion that Economy 7 isn't worth it? That's what I'm using and I can't see why it's not cheaper to charge when the rate is lower.

Surely the point about Economy 7 is that while the night time rate is cheap, the daytime rate is usually more expensive than a standard tariff - you do need to consume quite a lot more electricity at night than you do in the day for the sums to come out in your favour. When we bought the Outlander, I did the sums based on our anticipated pattern of usage and the E7 tariffs that were published - I came to the conclusion that we might save a small amount overall, but not enough to be worth the hassle of switching and it would not have required me to do many charges during the daytime to actually leave me worse off.

I did similar calculations, and as I work from home a lot, I worked out that I'd be £20 off worse per month. I think the only people that really benefit from this nowadays are people with Storage Heaters as all modern white goods are so efficient, and the things that are high consumers now need to be on during your daytime hours. Plus the number of consuming devices like PC's, laptops, tablets, mobile phones, handsfree phones, TVs in multiple rooms, etc, means that the number of daytime consuming units is far higher than what it was 10 years ago.

EDF have a modified Economy 7 tariff called 20:20 which kicks in earlier than midnight (about 9pm I think) cutting off about 7am. The difference is not as large between the 2 rates, i.e. the night rate is higher than Economy 7 but the big advantage can be the night rate applies all weekend - when many of us might be using more energy (especially charging our PHEV ) during the day.

 

[rtw]

It costs me 77p for a full charge at night and £1.21 in the daytime. The equivalent single rate tariff would be £1.10 for a full charge. So even if I need to do 2 full charges during the day and 1 at night, I'm on the right side albeit very marginally.

I guess the main saving is on those days where a single night time charge is enough for that day's driving.

Ozukus does makes an valid point about all the other stuff plugged into the house though. It does make me wonder if the small saving made on charging the car overnight is overshadowed by all the other consumption, since the storage heaters were removed from here a long time ago.

 

[Ozukus]

It costs me 77p for a full charge at night and £1.21 in the daytime. The equivalent single rate tariff would be £1.10 for a full charge. So even if I need to do 2 full charges during the day and 1 at night, I'm on the right side albeit very marginally.

I guess the main saving is on those days where a single night time charge is enough for that day's driving.

Ozukus does makes an valid point about all the other stuff plugged into the house though. It does make me wonder if the small saving made on charging the car overnight is overshadowed by all the other consumption, since the storage heaters were removed from here a long time ago.

As an FYI Sainsburys Energy rate for an all day tariff is 9.9p per KWh so expect if you look around you may find that you can get a better flat rate and be able to ignore when you charge. Effectively your saying your saving about 30p per day for your overnight charging, however if you look at your consumption all those daytime units, routers, phones, TV's and so forth will probably greatly benefit from a reduced daytime rate.