How will I heat my water when THTC meter swapped out?

Hi,

Apologies, I'll try to be a bit clearer - the heaters I have now are two (one in each bedroom) electric ones that give instant heat, they aren't storage and all associated storage ones have been removed and I have a wood burning stove.

It's really just my hot water I'm concerned about - I think E10 may be best given the timings it provides cheap electricity as it's handy to have a period during the day and evening in case I need to heat up the water (baby on the way) but also the overnight hours.

What's not clear is whether I now need to arrange rewiring of the water tank to take advantage of the time periods on E10 or E7 if I went for that which will be an additional cost as I currently can't see any way to set the hot water times on the existing system so presume it's hard wired to the meter.

I don't think it'll be hard wired to be cheap E10 or E7 at any time would it? So effectively I will need some form of timer so the hot water isn't just heating up at say 1pm in the afternoon?

The cost I was referring to was the potential rewiring, not anything else.

Sorry, I'm not sure what extra details are needed as thought my original message was clear, as in I needed to understand how the hot water was going to work when I don't have storage heaters to worry about as I can't see any way at the moment to set it to what either E7 or E10 will be

No need for apologies - you couldn’t possibly guess what I might ask! 
  

Right. If the stove is your principal mode of heating, I’m still not convinced that you need to be on a multi-rate tariff. Your hot water tank will probably have, say, two 3kW elements, one main one at the bottom of the tank and the other near the top for a daytime boost. It depends how big the tank is how long it takes to heat up and consequently how much energy it uses in doing so. A 120l tank would use about 6 kWh to heat up from cold (e.g. from 10º to 50º), so a couple of hours for the main element. Unless that represents more than about 35% of your total daily consumption, you’d probably be better off on a standard rate. I’m sorry I didn’t ask where you lived (it’s item 1 on the checklist I haven’t yet found), because I’d then have been able to do this calculation more accurately.

I don’t anticipate any major problem with the wiring to the water heater in either case (multi-rate or single-rate), but photos of your current set-up would certainly help: a decent one of the current meters showing all the cables to and from them, and of the consumer unit(s) (‘fuseboxes’) clear enough for us to read the labels on the breakers. Keep the photos safe after posting them here: it would be a good idea to send them to OVO support when you make your meter exchange booking. A photo of the water heater control and switch(es) would be good, too.

Would I not be more expensive overall to have a standard rate for heating my water as if I manage to time it to only use E10 or E7 times then it would work out cheaper than just standard as a single rate would likely only have a few pence difference between the 'day' rate and 'cheap' rate on E7 or E10?

I'm in the MPAN 17 area.

I just thought as well, the engineer said if he changed the meter then it would trip due to the consumer unit that's in place (old I assume), so are OVO going to replace this as well given the smart meter will cause issues and things are having to change because the signal is being turned off and nothing to do with anything I'm doing?

I've included photos of the meter setup, consumer unit and the timer I have which only has the option to boost!

I still don't quite understand why I don't need to worry about the timer itself as I thought the meter will no longer tell the boiler (or whatever it does at the moment with thtc) to come on as there will be different off peak times and I'm assuming the hot water tank will just try to heat up continually unless I have a way of setting it to match the times of the smart meter?

Sorry I'm probably being a bit dense.

I’m afraid maintaining and replacing a Consumer Unit is Out-Of-Scope for OVO to touch. Even if it trips post-upgrade, it’s your problem to fix at your own cost. OVO can’t help you with that as you’d need a private electrician to do it. Likewise, OVO cannot contribute to the costs of such work - you must bear that cost yourself, even if the meter swap is forced on you. There’s no exceptions to these rules.

If you need a financial boost to get such work done, have a chat with Citizens Advice - they can probably find you a funding source that may be able to assist.

Please see the guides below for more details:

• Who owns what? - Your guide on cut outs, meters, fuses and who's responsible Tutorial

Unless you go to Flat Rate, the new Smart Meter would continue to control the operating times for any heating/hot water loads automatically, just like your current setup does now (except at different times to before).

Thanks very much - they’re really helpful.
    

I’d guessed as much!
  

You’d have to do some sums to work that out. Don’t forget that everything other than whatever’s on at offpeak times will be at a rate higher than the standard (single) rate. That’s why I mentioned ‘more than 35% of total consumption during offpeak time’. 

Time to dig out your bills for the past year. I don’t know what sort of THTC plan you’re on - you’ll see there are several varieties. However, you should be able to see the quantities in kWh used at day/normal/anytime/peak rate on the one hand and night/low/heating/offpeak on the other. You didn’t say how long ago you removed the storage heaters, but it would be most useful to find bills since then, when you’ve probably only had hot water on the heating circuit.

A very rough guide would be the 6 kWh I mentioned earlier to heat up your water tank. If the tank is twice as big, 6 kWh will become 12 kWh. A 120l tank is big enough to give one full bath or a couple of showers and a day or two’s washing up and other sundry usage. Only you know how much you use. What you want to avoid is having the immersion heater running constantly, which only helps to keep the starlings in the attic nice and warm.

The arrangement you currently have is for the water heater to be on the meter’s switched (offpeak) circuit, as you can see from the CU. A smart meter will ensure that this circuit is only active during offpeak hours. You’ll also see that there is also a breaker on the constant circuit - this is for the tank’s upper immersion heater, only operating when Boost is selected, and charged at the higher rate along with everything else.

The direct heaters in the bedrooms will probably be the most expensive appliances to run, of course depending on how long they’re on for. Another one to be wary of is a tumble dryer - it can be a real energy hog.

You’ll find the rates for the different plans on offer on this page: plans.ovoenergy.com

Now, if you did find that having the water heater running at offpeak times and rate while everything else you use out of offpeak hours is at the peak rate is likely to be less expensive than running everything at the single rate, go for  E7 or E10. Check the total annual cost in all three cases, bearing in mind that E10 gives you the option of running aforesaid tumble dryer and any other power-hungry appliance (cooker, hair dryer, hoover for example) in the afternoon or late evening at offpeak rates. The bedroom heaters could also be used in this way, e.g. an hour or two before 07:30 and before bed (and also in the early afternoon for the bairn’s nap!). 

Now, the water heater.

• On a multi-rate plan, this would be live for 7 or 10 hours, but only running until its thermostat switched it off. This might still be a bit wasteful, if for example the afternoon and evening sessions turned out to be unnecessary. 
• On a single-rate plan, you’d need to invest in a new timer that you could set only to run when you need it to. They’re not expensive, but the sparky you’d have to get to install it might cost quite a bit more than the timer itself. You wouldn’t necessarily need one with lots of bells and whistles. You might even find a simple 16A smart plug (13A may be too light) would do the trick, but you’d have to get sparky to install a socket instead of the hard-wired connection you probably have currently. Otherwise, a simple clockwork timer might do.   

Hi ​@nathaniel2040 ,

A warm welcome to the OVO Forum.

Thanks ​@Firedog and ​@Blastoise186 for your info here, really helpful as always. I’d just like to add ​@nathaniel2040 that you should contact our Support Team to ask them whether you’d be better off being on a single rate plan, rather than Eco7/10. They’ll be able to calculate your average usage against our current rates to assess whether it would actually be cheaper for you to be on a single rate tariff. Just to confirm, this wouldn’t mean that we’d have to alter the meter and its timings. We could still have it giving two readings on two registers, but could bill the entirety of this usage on one flat unit rate. This is known as a ‘P2 to P1’ tariff change.

It may be that a single rate plan wouldn’t save you money, but it's well worth you asking the question. I hope this helps.

Oh good… Now I find that elusive guide I was looking for…

Oh well, better late than never!

I’ll just quietly add it to my previous response too… And pretend that I never made that mistake...

Considering the engineer’s remark that “if he changed the meter then it would trip due to the consumer unit that's in place”, out of the millions of smart meters installed to date, I’ve seen a handful (<10) of instances of unexpected breaker trips reported. There has been no single cause or remedy established, and it’s not likely to become clear anytime soon. However, if it is indeed the EMF radiation from the communications hub that’s the culprit in some cases, the only factor I can detect from the photos that might be significant is the plastic CU enclosure very close to the meter, as opposed to a more modern steel one which should effectively shield the Type B RCDs from external radiation. Objecting to a smart meter installation on these grounds would IMHO be fanciful. 

Thanks for the replies everyone, really appreciate it as so helpful and has put my mind at ease a bit more when info received to date has been a bit patchy.

From a tariff perspective whilst there is a chance single rate could be cheaper, the extra work involved (separate timer, labour cost etc) I think E10 may be more appealing as I could actually load shift a lot of applicances so hopefully in turn save some money.

Electrician comments, completely understand but at the time I panicked so just took his word on it, but I think it's probably best to upgrade the consumer unit as it is old and probs best to change to the metal housing for reasons you mention anyway, I just thought it was odd he just wouldn't install the meter rather than say if that happens you'll need to reset but essentially get the unit replaced asap!

I'll get in touch with OVO to finalise the points mentioned so it's 100% confirmed (don't doubt you all, it's just useful should I end up having to go to the ombudsman if things happened to go wrong, but I'm sure they won't!)

Thanks again for the comprehensive help!

One thing I forgot in my last post: I see a 32A breaker labelled Shower. If you use an electric shower instead of one fed from the hot water tank, this is likely to be your single most expensive appliance. They’re often rated at  9-10 kW, so running that at peak E7 rate could prove very costly. A single 5-minute shower a day could cost £90 a year. In those circumstances, it would make economic sense to use hot water from the tank instead so long as there’s enough pressure. Then again, if you could tame yourselves only to use the electric shower during Economy 10 offpeak periods, £90 would shrink to £65.

Just another factor to consider, I’m afraid.