Hi ​@Mike1600 ,

Changing between E7/9/10 isn’t trivial I’m afraid. I’d strongly recommend you pick one option and commit to it, so you’ll definitely want to do your sums first. While it may be possible to change later, I don’t want to get your hopes up and then drop you off a cliff, so my honest answer is that you should assume you can’t switch between them right now, but may be able to in the future.

If it helps, I can ask the other Forum Volunteers to swing by - they’re better at the number crunching than I am.

Many thanks for your reply Blastoise186

Regards

No worries, you’re most welcome.

​@Nukecad ​@Firedog have you got a sec? Your number crunching skills absolutely crushes my own.

​@Blastoise186  Sorry, I haven't got myself familiar with the differences between E7/9/10 - TBH I though you would be the ‘go to’ for that kind of stuff given the RTS situation.

Maybe we need to find an ‘E#-tariff’ expert?

I think that Firedog is on E7 so may have more idea.

I agree with Blastoise that it’s best to try and get it right first time. As he says, it may not be trivial to switch plans later. If your father is in an area with good WAN communication, the installation should be simpler than otherwise.

Which plan is best depends very much on the circumstances. There are significant differences in the unit rates involved. Here are some of the factors to be taken into account:

• number, type, size and age of night storage heaters 
• type of water heater(s) (including electric shower) and associated controls
• other heating apparatus formerly running at a lower Heating rate, e.g. panel heaters, IR heaters, fan heaters
• other non-electric heating apparatus  
• other power-hungry electrical appliances: cooker, washer, dishwasher, dryer, dehumidifier, even hoover
• lifestyle: time of getting up and going to bed, daytime activity levels at home, acceptable degree of comfort
• number, age and degree of infirmity of occupants 
• financial vulnerability  
• other things I can't think of ATM.

You may be able to get some idea of the usage pattern from old bills, but they won’t be much use if there is a 24-hour heating circuit running at a reduced rate. That won’t be available in the future.

You’re welcome to come back and give us a clear idea of what your old man needs, an d we can probably make some helpful suggestions. Even so, you might well need the advice of a reputable heating engineer on how best to keep him comfortable at an affordable price. 

The difference is in the name, more or less - the number of hours electricity is supplied at ‘cheaper’ rates.

E10 typically has 4-5 hours during the night, then an early afternoon slot and a late evening slot to make up the ten. The actual hours vary around the country. 

E9 simply has 3 x 3 hours, allegedly 03:00-06:00, 12:00-15:00 and 19:30-22:30.

E7 is nominally 7 hours overnight, but may be an hour more in some places. The hours are usually contiguous, but in some places there may be a slot at peak rate in the small hours to catch the unwary.

Which is the best in any specific situation depends on all sorts of factors, as I’ve just listed in my reply to  ​@Mike1600. It’s not an easy decision to make without detailed knowledge of the situation, and money spent on good professional advice will usually be well spent. 

An example: is it better to go with old-fashioned night storage heaters which might work well with the E9 or 10 daytime offpeak slots to top them up, or to invest in newer ones that could operate effectively on the E7 overnight charge alone? The running cost differential could be substantial - £110 per year per 1500W heater at E7/E9 rates in Region 20*. Or perhaps trust the heaters to keep the house reasonably warm until teatime, and then use intimate fan or panel heaters at offpeak rates for more effective warmth while curled up in front of the TV in the evenings? Add water heating into the mix, and it all gets a bit complex.

*   A 1500W heater should be able to store 23 kWh charged at 3.3 kW overnight. 23 kWh/day for 180 days/year → 4140 kWh. OVO offpeak rates in Region 20: E7 18.52 p/kWh, E9 21.19 p/kWh inc. VAT. (£0.2119 - £0.1852) x 4140 = £110.54). A single heater like this is ostensibly capable of keeping a 15m² room warm.

Against this, you’d have to allow for being able to cook, shower and hoover at the offpeak rate during the afternoon and evening instead of at the peak rate of 27.77 p/kWh. As I said, it gets complicated.