Gas & Electric v All Electric

JP08

I've always been under the impression that gas central heating was significantly more cost effective than electric.

However, just been doing some "back of envelope" calculations based on our current utility bills and a few simple assumptions.

Came up with the following.

Current average monthly figures (based on 4 years consumption and today's prices) :
£48.35/month (317kWh Electricity Peak)
+ £6.60/month (90kWh Electricity Off Peak)
+ £51.21/month (1255kWh Gas)
+ £23.29 Service Contract
+ £6.94 Boiler replacement fund (assume £1000 every 12 years)
TOTAL : £136.38


Notional "All Electric" figures
assuming boiler above was 80% efficient - so 20% reduction in the kWh consumed for gas above.
Electricity consumption Peak / Off Peak is 30/70). No service contract required and storage heaters last and last and last (as they seem to).

The figures then work out at
£64.57/month (423kWh Electricity Peak)
+£72.13/month (988kWh Electricity Off Peak) 'originally had 423kWh due to a mistype
TOTAL : £136.70

I'm sure there's some give and take in the assumptions (eg no pump electricity, gas hob goes to elec) so a pound or two in error, but have I missed something fundamental or are the ongoing costs really broadly the same in practice ?

[Deleted User]

Where do the values for the electric heating come from?

You are replacing 1255KWh of gas heating with 439KWh of electric heating. That does not work as the electric heating would have to be over 200% more efficient than gas.

JP08

Sorry - mistype, should be 988. Will edit in the original post.

HappyMJ

JP08 wrote: »

I've always been under the impression that gas central heating was significantly more cost effective than electric.

However, just been doing some "back of envelope" calculations based on our current utility bills and a few simple assumptions.

Came up with the following.

Current average monthly figures (based on 4 years consumption and today's prices) :
£48.35/month (317kWh Electricity Peak)
+ £6.60/month (90kWh Electricity Off Peak)
+ £51.21/month (1255kWh Gas)
+ £23.29 Service Contract
+ £6.94 Boiler replacement fund (assume £1000 every 12 years)
TOTAL : £136.38


Notional "All Electric" figures
assuming boiler above was 80% efficient - so 20% reduction in the kWh consumed for gas above.
Electricity consumption Peak / Off Peak is 30/70). No service contract required and storage heaters last and last and last (as they seem to).

The figures then work out at
£64.57/month (423kWh Electricity Peak)
+£72.13/month (988kWh Electricity Off Peak) 'originally had 423kWh due to a mistype
TOTAL : £136.70

I'm sure there's some give and take in the assumptions (eg no pump electricity, gas hob goes to elec) so a pound or two in error, but have I missed something fundamental or are the ongoing costs really broadly the same in practice ?

They are broadly the same for LOW usage.

High usage customers will always save with gas central heating.

A household with gas central heating would not usually have an E7 supply so you should use standard rates for electricity in those circumstances.

£23.29/month for servicing is quite high. I've had quite a few repairs on my central heating systems over the years and it doesn't come to that much and that's including replacing the 3 way valve, the central heating pump, the gas valve and getting a gas safety certificate.

Although you've accounted for the efficiency of a boiler you also need to consider that an E7 heating system isn't that efficient either. Yes all electricity is turned into heat but that heat is not stored efficiently. The heat is emitted from the storage heater at the wrong time requiring extra heat to be input into the heater so that it can be used in the evening when it's wanted. You also need to account for additional heating used in other areas of the house such as the bathroom which is almost always using peak rate electricity.

You've also used winter months. You need to make the calculation over 12 months.

It's an extremely complex calculation to make.

I've played about with spreadsheets over the years and really it's only in the smaller 1 bedroom flats and studio apartments that the cost using either electricity or gas is very similar.

I live in a very well insulated EPC Band A 2 bedroom flat with gas central heating and the average duel fuel bill comes to £45/month over the year and the flat is warm. Main living area is boosted to 20 degrees whilst occupied (for about 4 hours/day) and the whole property including other rooms are no less than 16 degrees 24/7 usually 18 degrees. Average servicing costs of the 10 year old system comes to £10/month (paid by landlord), boiler replacement fund would be around £5/month - smaller boiler with life expectancy of 15 years (paid by landlord). If all electric on E7 the bill averaged over the year wouldn't be much more than £60/month but all paid by tenant.

JP08

Thanks for the reply, but some comments below :

HappyMJ wrote: »

A household with gas central heating would not usually have an E7 supply so you should use standard rates for electricity in those circumstances.

Ok - our house is odd - it has !

HappyMJ wrote: »

£23.29/month for servicing is quite high. I've had quite a few repairs on my central heating systems over the years and it doesn't come to that much and that's including replacing the 3 way valve, the central heating pump, the gas valve and getting a gas safety certificate.

British Gas 2 star heating and hot water system repair and annual service contract.

HappyMJ wrote: »

Although you've accounted for the efficiency of a boiler you also need to consider that an E7 heating system isn't that efficient either. Yes all electricity is turned into heat but that heat is not stored efficiently. The heat is emitted from the storage heater at the wrong time requiring extra heat to be input into the heater so that it can be used in the evening when it's wanted. You also need to account for additional heating used in other areas of the house such as the bathroom which is almost always using peak rate electricity.

Fair point - though I gather that more modern systems are somewhat better in this regard. But even so, fiddling with the peak / off peak figure and pushing that up to 50/50 makes the All Elec a "mere" 15% dearer.

HappyMJ wrote: »

You've also used winter months. You need to make the calculation over 12 months.

I'm afraid that's our average figures over the last 3 years - I had another thread going a while back in the DIY section about the thermal inefficiency inbuilt in the design of the house (chalet style so large areas of the roof inaccessible to insulate, dormers with low insulation, flat roofs on the dormers, a suspended wooden floor over a concrete float base with a that has a major airflow going on between the two. And no cavity wall insulation at this point in time)

HappyMJ wrote: »

It's an extremely complex calculation to make.

Yep

footyguy

JP08 wrote: »

I've always been under the impression that gas central heating was significantly more cost effective than electric.

However, just been doing some "back of envelope" calculations based on our current utility bills and a few simple assumptions.

Came up with the following.

Current average monthly figures (based on 4 years consumption and today's prices) :
£48.35/month (317kWh Electricity Peak)
+ £6.60/month (90kWh Electricity Off Peak)
+ £51.21/month (1255kWh Gas)
+ £23.29 Service Contract
+ £6.94 Boiler replacement fund (assume £1000 every 12 years)
TOTAL : £136.38


Notional "All Electric" figures
assuming boiler above was 80% efficient - so 20% reduction in the kWh consumed for gas above.
Electricity consumption Peak / Off Peak is 30/70). No service contract required and storage heaters last and last and last (as they seem to).

The figures then work out at
£64.57/month (423kWh Electricity Peak)
+£72.13/month (988kWh Electricity Off Peak) 'originally had 423kWh due to a mistype
TOTAL : £136.70

I'm sure there's some give and take in the assumptions (eg no pump electricity, gas hob goes to elec) so a pound or two in error, but have I missed something fundamental or are the ongoing costs really broadly the same in practice ?

Gas is significantly cheaper than normal rate electricity.

Gas is about 3-4p/kWh whilst electricity is about 10-15p/kWh

But after the inefficiency of gas is taken into account (older boilers may only be 60% efficient), then cheap rate E7 electricity comes about par at about 6p/kWh
(but then your normal/day rate may be about 10% higher than the equivilent single rate tariff unit charge.)

Of course there is no time restriction on when you may use the gas - it's the same low price 24/7.
If you find you need to use electrical heating outside of the low rate period, it will be considerably more expensive than gas.
(ignoring latest technology such as expensive heat pumps, etc)