Query re changing from oil CH to Electric Combi Boiler

chris1973

Electric Combi boilers use a lot of Electricity, with the actual boiler consumption rated at upto 15kw that means 15 units of Electricity per hour. Even off peak this will cost you 15 x 6p = £0.90p per hour or 15x 12p = £1.80 per hour during peak periods.

Of course it wont always be drawing power continuously, although it will for the first few hours whilst it heats the radiators from cold, then how often it switches on thereafter depends on the size of the boiler, the number of radiators, thermostat setting, and any heat storage. However if it is a combi boiler without any external water heat storage, then it will be cripplingly expensive, as the boiler will basically be working and drawing power continuously, constantly feeding water directly 'on demand' to every radiator, rather than pre-heating a 100 - 150 litre heat store, and then feeding the radiators from the central heat store.

The main problem is that you cannot rely on the E7 period being enough to heat your house for the rest of the day (even with a 150 litre hot water tank in place). Inevitably you probably want the house to be at its warmest during the day at weekends and the evening when watching TV, this inevitably means running the boiler for long periods during the peak rate period, which at 12p per hour is going to work out VERY expensive.

In addition, if you live in a remote rural property, especially one fed with overhead lines and its own LV pole mount transformer, you may want to check with the DNO that existing capacity exists to run an Electric Boiler from your supply. Often these transformers feeding single dwellings are only rated at 16 - 25KVA, which is normally enough with diversity applied in general domestic electricity use, but not so where a high demand Electric Boiler is going to be the primary source of heat. You may find they want another £7000 - £10k to uprate the supply. This probably won't apply if you live on a housing estate with plenty of Electricity capacity, but it will probably rapidly become an expensive issue if your property has its own supply, and if that supply was installed and specified 30 years ago, before high demand electrical appliances!.

Since you have E7 already, I can only suggest that you perhaps consider fitting E7 storage heating to work in tandem with your oil fired heating, and find an E7 tariff closer to 5p per hour for off peak rate.

This will mean that you will have storage heating charging overnight at 5p per hour, which should hopefully give off enough heat at least to last until late afternoon / early evening, meaning you only have to resort to using the oil fired heating during evenings in the colder months of mid-winter - you may also find that storage heating is enough to solely heat infrequently used rooms like bathroom and bedrooms meaning you can switch off a few radiators when running the oil fired CH, and just have the storage heaters running in these rooms.

You can also use an immersion heater during the off peak periods for water heating, rather than oil.

At 5p for Off peak electricity, its marginally cheaper than oil, whilst being 100% efficient in converting to heat.

This will basically remove any need to use Electric Heating at peak rates, as both E7 storage heating, your hot water requirements and oil heating will cost well under 12p per KW/H

muckybutt

Just to put things into perspective, we had air source heating installed when we got rid of our oil ch. In the first 80 odd days of use it used over £800 + of electric :eek:

Needless to say it isn't installed anymore !

nesssie1702

Chris1973 - thanks for the heads up regarding the power supply issue. It's certainly something for me to bear in mind.

Just got my last oil bill in and including VAT at 5%, it works out at 66p a litre.

It's currently an oil combi boiler that we've got in the house, so no external hot water tank at the moment and no immersion heater either.

[Deleted User]

muckybutt wrote: »

Just to put things into perspective, we had air source heating installed when we got rid of our oil ch. In the first 80 odd days of use it used over £800 + of electric :eek:

Needless to say it isn't installed anymore !

Hi, interested to hear what ASHP you had and type of heat emiters it was connected to? Cheers

chris1973

Just got my last oil bill in and including VAT at 5%, it works out at 66p a litre.

Even allowing for the lower efficiency which oil gives compared to the 100% given by electric heating, 66p a litre still works out a lot cheaper than peak rate Electricity @ 12p per KW/H and thats even before you take into account the initial costs of buying the Electric Boiler and having it installed.

Even with off peak E7 electricity, a large part of the consumption used by the electric boiler would be during peak times - i.e during the weekends and evenings, in real terms the electric boiler would cost you around 30% - 40% MORE than the oil filled one, even allowing for its better efficiency

Unfortunately Electricity is always going to be an expensive form of heating, largely because we have to buy and burn another fuel (Gas / Coal) in order to generate and produce it