gas vs electric

ButtercupDaisies

We're looking at 2 apartments, very very similar.

The first is dual fuel and the second is all electric.

The first has an estimated usage of 12,000 kWh per year (gas + electric).
The second has an estimated usage of 5000 kWh per year (electric).

I've checked on the EPC certificate and Moneysupermarket.

How can there be such a huge difference between the usage of gas and electric?

GingerTim

Is the second better insulated than the first?

CSI_Yorkshire

Because per kWh electricity is more efficient at heating than gas.

"Average" all-electric household is about 4200kWh.  "Average" dual fuel household is 2900kWh electricity and 12000kWh gas.

Although remember, per kWh the cost of electricity is several times higher.

ButtercupDaisies

GingerTim said:

Is the second better insulated than the first?

No, barely 

QrizB

CSI_Yorkshire said:

Because per kWh electricity is more efficient at heating than gas.

Although only 10-20% more efficient assuming a boiler fitted in the last 15 years. 5000kWh of gas might be equivalent to 4000kWh of electricity.

CSI_Yorkshire said:

"Average" all-electric household is about 4200kWh.  "Average" dual fuel household is 2900kWh electricity and 12000kWh gas.

Those figures also reflect that the average all-electric household is smaller than the average dual-fuel one. There are lots of all-electric studio flats and not many all-electric 3-bed semis.

Gerry1

CSI_Yorkshire said:

Because per kWh electricity is more efficient at heating than gas.

True, but only marginally.  100% vs. perhaps 90% for a modern condensing boiler.

CSI_Yorkshire said:

"Average" all-electric household is about 4200kWh.  "Average" dual fuel household is 2900kWh electricity and 12000kWh gas.

Apples and pears. That's because all-electric households are usually small flats with relatively few occupants.  Detached houses with familes are unlikely to be all-electric; if mains gas is unavailable they're likely to use oil, LPG or solid fuel for heating.

Edit: Beaten to it again by Qrizby !

Gerry1

ButtercupDaisies said:

The first has an estimated usage of 12,000 kWh per year (gas + electric).
The second has an estimated usage of 5000 kWh per year (electric).

Estimates are merely estimates and could be seriously inaccurate.

Unless they're both brand new it might be better to try to establish historical usage, but even that may be of limited use if the occupants and lifestyles aren't directly comparable.

CSI_Yorkshire

@Gerry1 & @QrizB

So what is your advice for the OP then?

Two flats, "very very similar" with reportedly the same insulation, where the difference in energy usage is stated as (very roughly) spread by about the difference between the mythical average users.

Your expectation is that the dual fuel estimate and the all-electric estimate should be essentially no less than 10% apart?

QrizB

CSI_Yorkshire said:

Gerry1 & QrizB
So what is your advice for the OP then?

Personally, I'd say that energy performance certificates are an inexact science. Similarly, suppliers records of previous occupants' energy use aren't necessarily typical.

I live on a street of mostly identical 50s semis. EPCs for those properties vary from C to E and energy use by a factor of almost 3.

If the OP's properties are as similar as is claimed, I would expect them to have similar net heat and power demands for any given occupants.

Gerry1

Without knowing more (e.g. is it a 'forever' home or just for the next few years) it's difficult to be specific.

Personally I'd never consider an all-electric property; it's a very expensive form of energy for heating, and there would be no alternative heating in the event of rota power cuts or a prolonged failure of the supply.

Scot_39

You would have to assume gas was very inefficient to get those two figures aligned for identical properties.
Not just build standards, but say same level (ground, any middle or top), same rain, wind and sun exposure etc

Ofgem medium use duel fuel cap is c80% gas (12000kWh) , c20% electric (2900kWh).

Drop to match your duel fuel example c12000 total, get c9600 gas for heating and hw / cooking ?  and c2400 electric for rest.

If took that same 2400 kWh for rest out of the 5000 for all electric flat - would leave only 2600 for main heating etc

It's a bit of a simplistic way of doing it - but it does clearly suggest a significant potential mismatch between the two figures.

If factor in gas inefficiency cf electric,  took the 9600 level and applied say a pessimistic gas 75% efficiency (a modern condensing boiler should be better, but radiator pipes and radiators against walls and under windows can add losses too) - would only reduce output by c2400 kWh.(85 % efficiency, loss drops to c1400kWh , 90% eff,sub 1000kWh).

So arguably 12000 flat would have the 2400 misc core electric + 7200 true heat input = 9600 total.
Almost Double the 5000.

So something to my mind doesn't stack up.
But then I'm no energy surveyor.

And remember, in any case gas is going out of favour medium term - no GCH in new builds soon, no new replacements c2035 ?? in Eng,

Harvie et al trying to accelerate the demise even quicker in Scotland.  RW media I suspect with some exageration saying could stop, but many more saying could make a property with gas boiler more difficult to sell or certainly rent out etc etc.

Cost ratios now are not the only consideration.
Your own eco politics matter.
As do those of current and future govts.
And who knows if current margin / ratio of gas to electric per kWh will increase or fall in future.