The standard supply for a new house seems to be circa 18KVA single-phase. I have a client who needs to make application for a supply for a new build house at 400m2 with the only certain information being that an air source heat pump is to be used for heating. The client simply does not know what the electrical loading might be. The house is only coming out of the foundations but the DNO supply may take many months as the house is in a relatively remote rural location, thus loading details are required before the DNO will consider progressing the proposal. It is a big house, but that is what it is, just a big house. I am inclined to advise a standard supply but 3-phase as with a large AS heat pump, maybe shower, cooking and perhaps an EV or two, 18KVA wouldn't be long being gobbled up. As we move towards a higher reliance on electric as a power source for some heavy current-using equipment, it might be that 18KVA is no longer a realistic standard supply for even the smaller property.
Even a 3 phase 100 amp supply might be marginal with a couple of 22Kw vehicle chargers. ...
I am pretty sure that the DNO will not contract to supply 69 kVA. I am not quite sure how ADMD is applied to a single property, but I got 30 kVA.
More than one 22 kW charger seems silly. That's about 80 - 100 "mph" so unless somebody is spending several hours per day behind the wheel, that sort of power is just not needed. Even with a 100 mile round-trip commute (and no charging at work), each car would only be charging for an hour a day. One will do with perhaps a second 7 kW charger so two vehicles may be charged simultaneously.
I am sure that diversity will take care of things, but let's suppose that it doesn't. If the occupier is out for 8 hours per day and asleep for another 8, the only substantial use will be for 8 hours. Let's say that an average of 50 A per phase is consumed. That is 50 x 3 x 8 x 0.23 = 276 kWh per day. Let's assume a tariff of £0.15 per kWh. That comes to £41.40 per day or £15k per year!!!
That £15k per annum includes the electricity used to power a couple of cars instead of petrol or diesel, which could easily explain away at least half of the total if not more.
Ventilation of this property of 1 air change per hour will need far more than Andy has allowed
You might have a point there - I had attempted to include ventilation losses at 0.5 ACH (which I think is a pretty usual target), but had missed out one factor in that calculation ? Apologies I should have spotted that earlier (one of the danger of spreadsheets over manual calculation!). My revised figures now show about 4.5kW for ventilation and about 10.6kW overall. A large new build could well incorporate mechanical heat recovery ventilation though which should easily reduce the ventilation losses by more than 70% (at the expense of a few tens of watts for running the fans and controls). As before, insulation better than minimum building regs requirements could reduce the figures very substantially still.
Building technology has moved along quite substantially in the last 15 years or so - new builds are now incorporating levels of insulation that a generation ago were thought to be physically almost impossible and increasing fuel prices and likeley future fuel scarcity are making high levels of insulation more and more attractive, especially in the self-build sector (what will you run your gas boiler on once North Sea gas runs out?).
I would hope that a reasonably prestigious new build wouldn't think of installing tacky instantaneous electric showers either - they're really just a bodge to get around getting a decent shower out of traditional UK low pressure hot water systems and inefficient boilers - they're virtually unknown in much of the rest of the world where high pressure hot water has been standard for generations. If you are heating water by electricity then a storage system giving high pressure hot water and heated off-peak usually makes a lot more sense.
Building technology has moved along quite substantially in the last 15 years or so - new builds are now incorporating levels of insulation that a generation ago were thought to be physically almost impossible and increasing fuel prices and likeley future fuel scarcity are making high levels of insulation more and more attractive, especially in the self-build sector (what will you run your gas boiler on once North Sea gas runs out?).
Coal gas! ?
It's a bit windy here today, so the windows are rattling. That certainly wouldn't happen in a new build. When I first heard about pressure-testing new houses, I thought that somebody was having a giraffe, but no, 'tis true. That is despite the presence of open chimneys, ventilation bricks and, of course opening windows. ?
Two EV chargers each of 22 Kw may sound excessive, but if that is what the client wants, then the electrical installation must be able to supply that load, and the heat pump, and a reasonable loading for other appliances.
Since the EV chargers and the heating will consume about 70 amps per phase, provision of a three phase 100 amp supply looks a bit marginal.
After the EV charging and heating is considered, we are in effect left with a three phase 30 amp supply for everything else which sounds inadequate, unless some form of load limiting is used.
A house of this size may imply either a large family, perhaps with more than two electric cars, and the demand for multiple showers, or alternatively might suggest live in staff.
Even if electric showers are avoided, multiple showers from stored hot water is a significant demand. I doubt that a single 3kw water heater would cope with that load.
A large household might well have multiple washing machines and tumble dryers.
I consider it probable that an off peak tariff would be used for EV charging and water heating. One supplier at present have an attractive sounding tariff that offers a heavily discounted rate for 5 hours overnight.
Adoption of this or a similar tariff might suggest a MINIMUM loading of 80 to 85 amps per phase during such hours.
That £15k per annum includes the electricity used to power a couple of cars instead of petrol or diesel, which could easily explain away at least half of the total if not more.
Electric cars still have “fuel” costs.
Andy Betteridge
Take this Renault Zoe on EBay as an example, ball park figures appear to put the lifetime running costs at double those of a similar car with a petrol engine.
2014 RENAULT ZOE Dynamique Intens 5dr Auto - 10500miles, 87bhp
Without battery, you need to rent a battery from Renault. Prices start
