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Electric boilers - effect on power demand of a block of flats

donf
Hello there.


I would like to  know if anyone on the forum has done a study of or knows about an existing study of the impact on power demand of introducing electric boilers to block of flats. 


I have been tasked with estimating the impact of a gradual migration to electric boilers for central and water heating in a modern block of flats. Nearly all of the flats currently use gas fired combi boilers.


I then have to present this information to UK Power Networks so that they can asses whether or not an increase in capacity to the building supply might be needed in future.  Finally I need to put any recommendations to the owners' management board.


Clearly electric boilers will have some impact on power demand.


I can start with an estimate of current power demand (worst case) for a typical flat.  To that end, I'll be doing a survey of about 25% of the flats to come up with a figure.


I can then apply the IET Electrical Installation Design Guide diversity calculations for a typical flat and then the building as a whole using figure 3.4 (IET Electrical Design Guide Nov 2008 page 33).


I can then do a second power consumption exercise adding the demand of a typical electric boiler per flat and then the whole building.


However, it's not clear to me if this approach will be suitable for a massive migration to electric boilers.  I need to be sure of my ground if I approach UK Power Networks with a demand figure.


If we look at the usual peak use of heating demand (morning and evening) a building full of electric boilers, to me, could add a significant load to existing street fuses and possibly even cable capacity.


I would be grateful for any suggestions and experience people could bring.


Kind regards


donf










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    I do not have a simple answer for you I'm afraid, but will make it more complex. Electric boilers generally are not an efficient use of electricity, compared to say heat pumps, and so are not good news for the building energy rating. Certainly for rented flats at least, the Lot 20 rules and EPC rating requirements combine to make a very confusing mix - off peak storage heating being cheapest to run of course if you have no gas, but electric vehicle charging is set to eat into that.


    I caution that a simple exchange of all gas boilers to electric in an existing building is unlikely, even if keeping the radiators and so on looks attractive to begin with, as the economic drivers both for owner occupiers and sub-letters are not in that direction - though in 5 years they may be of course.


    They also tend to be lower rated, so maximum water flow and heat up times are all poorer -  a combi boiler may be 30kW on gas ,and yet the largest electric model that does not need a 3 phase supply will be lucky if it is half of that. A small one for a bedsit may be more like 4 to 6kW.


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  • 0
    I do not have a simple answer for you I'm afraid, but will make it more complex. Electric boilers generally are not an efficient use of electricity, compared to say heat pumps, and so are not good news for the building energy rating. Certainly for rented flats at least, the Lot 20 rules and EPC rating requirements combine to make a very confusing mix - off peak storage heating being cheapest to run of course if you have no gas, but electric vehicle charging is set to eat into that.


    I caution that a simple exchange of all gas boilers to electric in an existing building is unlikely, even if keeping the radiators and so on looks attractive to begin with, as the economic drivers both for owner occupiers and sub-letters are not in that direction - though in 5 years they may be of course.


    They also tend to be lower rated, so maximum water flow and heat up times are all poorer -  a combi boiler may be 30kW on gas ,and yet the largest electric model that does not need a 3 phase supply will be lucky if it is half of that. A small one for a bedsit may be more like 4 to 6kW.


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