Do I Stick With Gas Central Heating?

HappyMJ

rogerblack wrote: »

My current best rate for gas is about 3p/kWh - electricity is 14.7p.

This would take the cost for heating to about 3.5p/kWh - for the heatpump.

Still more expensive than gas, though comparable.

Where are you to get such high electricity? Npower (go fix 12) is 9.1p, Utilitia is 9.2p, Scottish Power 9.4p, Sainsburys 9.95p, OVO is 9.98p.

The most expensive electricity is Ebico at 13.81p/kWh

If a house had a heat pump then a standard rate is most likely the best tariff. I would not recommend an E7 tariff.

Cardew

rogerblack wrote: »

Good air-source heat pumps have an efficiency of around 4:1 - they produce 4 units for every 1 of electricity.

My current best rate for gas is about 3p/kWh - electricity is 14.7p.

This would take the cost for heating to about 3.5p/kWh - for the heatpump.

Still more expensive than gas, though comparable.
The problem happens when it gets colder.

Both the heat pumping capacity - how much heat it can produce - and the efficiency - how much it takes to produce that heat drop.

This can easily mean that unless the system is properly sized, you fall back on really expensive 'boost' heaters, which are nothing more than normal electric heaters.

A system properly sized for winter loads of a house, that is one of the more efficient ones on the market (otherwise it won't come close to gas) is likely to cost several thousand pounds.

Roger,

Heat pumps might have a theoretical COP of 4.0( 4 units output for 1 input) at mild temperatures but in practice never achieve those figures.

The Energy Saving Trust carried out a year long trial of loads of heat pumps and the average was a COP of 2.2 with the best at 3.3 and the worst at 1.2.

A huge factor in the economics when considering heat pumps is the capital cost of installation. An ASHP can cost well over £10,000 and a GSHP £20,000. Invest £10,000 @ 3.5%(after tax) and you lose interest at a rate of £350 a year which goes a long way toward the cost of gas. Borrow that money, or lose interest on a long term ISA and the costs are far more.

In the 'real world' heat pumps don't compete with gas.

Pincher

DSB1972 wrote: »

Is there another way?
Is there any info out there to EASILY compare boiler costs to electric stated above or

Is there another unit which can replace a boiler that doesn't use gas? to provide heat & hot water.

I know some countries use air conditioning summer & winter, that's energy efficient but lots of units round the house.

A Universal Question, like:

"Can I have a car that doesn't cost a fortune. I just want to be able to go places."

or to re-phrase:

"I just want to keep warm, why do I need a 50kg machine and leaky pipes that cost thousands, and I can't even take it with me when I move house?"

Apart from becoming a Buddhist monk, who is not allowed material possessions, and live in a cold cell, I haven't found an alterntive that is easy or cheap.

The Grand Design approach of building a whole house for £200,000 so you don't need heating does not count, as it is neither easy nor cheap.

A viable approach is to marry and move in with somebody who already has a Passivhaus. As this means turning gay and moving to Germany, I hesitate to implement the plan.

HappyMJ

Cardew wrote: »

Roger,

Heat pumps might have a theoretical COP of 4.0( 4 units output for 1 input) at mild temperatures but in practice never achieve those figures.

The Energy Saving Trust carried out a year long trial of loads of heat pumps and the average was a COP of 2.2 with the best at 3.3 and the worst at 1.2.

A huge factor in the economics when considering heat pumps is the capital cost of installation. An ASHP can cost well over £10,000 and a GSHP £20,000. Invest £10,000 @ 3.5%(after tax) and you lose interest at a rate of £350 a year which goes a long way toward the cost of gas. Borrow that money, or lose interest on a long term ISA and the costs are far more.

In the 'real world' heat pumps don't compete with gas.

Air-to-water heat pumps can cost up to £10,000 for a large system but a simple small 3-4kw output air-to-air heat pump only costs up to £2,000 and is suitable for a living area.

rogerblack

Cardew wrote: »

Roger,

Heat pumps might have a theoretical COP of 4.0( 4 units output for 1 input) at mild temperatures but in practice never achieve those figures.
<snip>

In the 'real world' heat pumps don't compete with gas.

That's specifically why I said expensive.
The very best on the market probably can supply a ratio of 4, over an average heating season.

For example, a good Toshiba inverter air-air heatpump.

Input Output COP
Temp watts

20 3340 6.3
15 3020 6.1
10 2690 5.8
5 2330 5.4
0 1750 4.8
-10 1400 4.3
-15 1080 3.7

This is for the most expensive inverter driven heatpumps, but it indicates potential pitfalls even for them.

Firstly, it shows that for this particular device, it's probably going to be more-or-less economic compared to gas over the whole range.

(for the best gas/electric deal I can get, others prices may vary)

However, it also shows a nasty gotcha.
The above system will have '3.3kW' on the sticker.
If you actually have a heating need of 3.3kW in this room when it hits -10C - oops.

You now find that it only outputs 1400W, and you need 2000W of electrical heat to top it up, and produce 3400W, using about 2400W - for an overall performance of little better than one.

It's now almost more expensive than gas.
So, you actually - if you need 3.3kW to heat the room in the coldest parts of the year - if you don't want to rely on electric heat - need about double the watts on the sticker (which almost doubles the cost).

And the above table is for the best available heatpumps.

More 'economy' ones can start out at half the efficiency, with it dropping to 2 (twice the price of gas) at only 5C outside, and will suffer icing too.
This will be essentially useless for almost all year-round heating purposes.

Then there is the fun issue that this massive investment is likely to be worthless in 15 years or so time at most, as it fails.

rogerblack

HappyMJ wrote: »

Where are you to get such high electricity? Npower (go fix 12) is 9.1p, Utilitia is 9.2p, Scottish Power 9.4p, Sainsburys 9.95p, OVO is 9.98p.

The most expensive electricity is Ebico at 13.81p/kWh

If a house had a heat pump then a standard rate is most likely the best tariff. I would not recommend an E7 tariff.

Scotland.
Go fix 12 - for someone using 4000kWh/year electricity only - and including the standing charge is 13.6p/kWh.

I will note that an interesting possibility is a heatpump on E7.
But this has so many issues of its own that it's almost never practical.

HappyMJ

@rogerblack That's actually a 2.5kW output heat pump. The rating is measured at 7 degrees outside.

HappyMJ

rogerblack wrote: »

Scotland.
Go fix 12 - for someone using 4000kWh/year electricity only - and including the standing charge is 13.6p/kWh.

I will note that an interesting possibility is a heatpump on E7.
But this has so many issues of its own that it's almost never practical.

I see so it's not the secondary rate but the entire bill divided by 4000. I think someone who had a heat pump as a main source of heating in the living room would use way more than 4,000kWh per year.

Cardew

rogerblack wrote: »

That's specifically why I said expensive.
The very best on the market probably can supply a ratio of 4, over an average heating season.

For example, a good Toshiba inverter air-air heatpump.

Input Output COP
Temp watts

20 3340 6.3
15 3020 6.1
10 2690 5.8
5 2330 5.4
0 1750 4.8
-10 1400 4.3
-15 1080 3.7

This is for the most expensive inverter driven heatpumps, but it indicates potential pitfalls even for them.

Firstly, it shows that for this particular device, it's probably going to be more-or-less economic compared to gas over the whole range.

(for the best gas/electric deal I can get, others prices may vary)

However, it also shows a nasty gotcha.
The above system will have '3.3kW' on the sticker.
If you actually have a heating need of 3.3kW in this room when it hits -10C - oops.

You now find that it only outputs 1400W, and you need 2000W of electrical heat to top it up, and produce 3400W, using about 2400W - for an overall performance of little better than one.

It's now almost more expensive than gas.
So, you actually - if you need 3.3kW to heat the room in the coldest parts of the year - if you don't want to rely on electric heat - need about double the watts on the sticker (which almost doubles the cost).

And the above table is for the best available heatpumps.

More 'economy' ones can start out at half the efficiency, with it dropping to 2 (twice the price of gas) at only 5C outside, and will suffer icing too.
This will be essentially useless for almost all year-round heating purposes.

Then there is the fun issue that this massive investment is likely to be worthless in 15 years or so time at most, as it fails.

We are a cross purposes to a certain extent.

Firstly it isn't much good quoting theoretical COP figures for the 'stand alone' air to air ASHP. The 'killer' for all these ASHPs when installed is the defrost cycles.

In any case what is the point of such a low powered ASHP and no facility to heat water for baths etc. You need to throw those costs into the equation.

Also when considering running costs(or savings) you should only use the tier 2 rate and ignore the daily standing charge or tier 1 rates - that will be 'used up' anyway