Economy 7 metering query

[Aragorn84]

I have an electric car, which clearly uses a fair chunk of electricity for charging. As a result i wanted to switch to Economy 7 to benefit from cheap rate electric at night for charging the car.

So i had Scottish (British) Gas out this morning to fit an Economy 7 meter.

The guy looked at my wiring and started going on about having to get an electrician in to connect up a new board for the off peak loads.

I told him it was for charging the car, and that the wiring was fine as it was. He then said that if i wanted to charge the car on cheap rate, i'd have to connect the car charger DB directly to the "off peak" connection on the meter.

I pointed out that the whole house should switch to cheap rate at during the off peak hours, so i can run my washer and dishwasher etc on the cheap rate as well and he said that no, only the loads connected to the off peak terminal of the meter would get the cheaper rate, and if i wanted the washer and dishwasher on cheap rate, they then wouldnt work during the day as that circuit would be unpowered, and that i would only be able to charge the car at night...


Now this goes completely against how i understood economy 7 to work. I understand that theres an OPTION to have a dedicated off peak connection on the meter, so dumb storage heaters and the like dont need any additional switchgear, but as i understand it, the whole supply should switch over to E7 at night time.

Can anyone confirm this? I told the guy to leave it just now while i clarified the situation.

 

[Taylortwocities]

I don't have Economy 7, and I am not in Scotland, but I am an electrician and there are several types of "Economy 7" system. What you have, and what is available, seems to vary from supplier to supplier.

I have seen two main types

1. This is as your meter installer has tried to connect. You have a meter and this has two outputs and two meter displays. One output is on 24/7. This powers your house (sockets and lighting etc) at one tarrif. The second (offpeak) output is time controlled and is only powered up overnight. this is designed for things like storage radiators.
To use this sort of meter for your car charge, then he is correct. You need a separate consumer unit for the off peak output to connect to your car charger socket. Of course you aren't going to be able to use this during normal daylight hours.

2.. This system (I think its called a white meter, but I could be wrong) is what you are after. It meters electricity at two different tariffs, a more expensive one during the day, and a cheaper one at certain times. It has only one output, for everything, and it is up to you to fit timers, or to use your high-current appliances during cheap rate times.

You need to go back to your electricity supplier, whoever that is, and discuss if they offer the second option.

Please be aware that if you go for an Economy metere option, the cost of electricity used during the day is increased. So you need to do your sums, it may not be worth the additional cost if your 'offpeak' consumption is relatively small.
I seem to remember somewhere that your off peak consumption needs to be more than 20% of your total to make an economy tariff worthwhile.

 

[Doggit]

Now this has brought up an interesting conundrum for me. My mother has a dedicated circuit for the storage heater, but puts the dishwasher on at night to get the cheap rate, but she may not be getting it.

I have a property that I rent out that had a dual rate meter, and the tenants put the tumble dryer on at night to get the cheap rate, and that was just one curcuit. But they soon changed it to a standard rate system, as the cheap rate savings didin't justify the higher day costs. You know what you currently use, and what the car will cost to charge, so you should be able to work out if there are any saving s to be had before you go ahead.

 

[Aragorn84]

I've asked around on the electric car forums and no-one else seems to have this issue, thye've just asked for "economy 7" and got what i expected to get. Supplier seems to barely know whats going on and the meter guys are clearly useless as well.

If there are two types of meter, the idiot that came out should have known that... All he tried to do was tell me to get a smart meter, which is completely pointless as BG dont offer off-peak metering with their smart meters.

I guess i'll need to call them again, or switch suppliers and see.

Doggit: I've done the sums already. I have an eMonCMS logging my power use over the last 5 months, and dumped it all into a big spreadsheet. Even without charging the car, theres a very slight advantage to Economy7 (a pound or two over the last 3 months) with the current rates i'm being offered, and more advantage would be had if i were to always put the dishwasher and washing machine on at night, as currently we just stick them on whenever. Add in charging the car and its much better.

 

[Aragorn84]

a guy on the EV forum posted this pic of what he has

 

[Taylortwocities]

a guy on the EV forum posted this pic of what he has

Yes, that has one single output and two time-based tariffs. So thats the one you are needing.

 

[ban-all-sheds]

I have an electric car, which clearly uses a fair chunk of electricity for charging. As a result i wanted to switch to Economy 7 to benefit from cheap rate electric at night for charging the car.

Be aware that every single new EV purchase brings forward the day when not only will you not pay less to charge it than at normal rates, you'll pay more.

 

[Aragorn84]

I'll plug it in at 6pm then if they're going to charge me more to plug it in at 3am

 

[JohnW2]

Please be aware that if you go for an Economy metere option, the cost of electricity used during the day is increased. So you need to do your sums, it may not be worth the additional cost if your 'offpeak' consumption is relatively small. I seem to remember somewhere that your off peak consumption needs to be more than 20% of your total to make an economy tariff worthwhile.

Unfortunately, that's over-optimistic. The break-even point for E7 is usually at 33%-35% of total consumption during the off-peak hours.

Kind Regards, John

 

[ban-all-sheds]

I'll plug it in at 6pm then if they're going to charge me more to plug it in at 3am

It's not the "when", it's the "what".

Electricity for charging EVs will cost more than electricity for your house.

 

[Aragorn84]

Umm... Its electricity, coming out a socket, into a load. How on earth are they going to charge more for the special electricity that goes to the car?

The powers that be may well devise a scheme to recoup the money lost from fuel duty, but its surely likely to be some sort of road charging or mileage based scheme.

 

[EFLImpudence]

That will be what 'smart' meters will do.

That's why the companies and government want you to have one.

 

[Aragorn84]

I still dont see how a smart meter can tell whats connected to it.

Smart meters might well allow them to introduce more granular time of use tariffs, it still doesnt allow them to discern the difference between a 3 bar fire plugged into the wall, and a car charger.

Unless you have some sort of smart charger as well, but why on earth would you choose to use one of those if it meant higher bills...

 

[EFLImpudence]

Unless you have some sort of smart charger as well, but why on earth would you choose to use one of those if it meant higher bills...

When the Government has to replace fuel duty, perhaps that's all there will be.

 

[roasty]

I did exactly the same, switched to E7 when I got my electric car.
Had the same conversation with the meter guy too.
There are two types of meter. 4 terminal - which means that the whole house goes onto E7 at midnight etc.. and a 5 terminal one with effectively 2 output 'lives' one for E7 and one for the rest of the time.
The second one is the one you don't want.

When I chatted to the meter man, he had both on his van, I thought he'd be far more familiar with the idea of electric cars, but once I explained what I wanted, i.e the same as you, i.e the whole house to switch over, then it was ok.

Good luck