Cheaper alternative to heat pumps

Lapiz

If the government switched the green levy to gas electricity should be cheaper so why all the emphasis on expensive heat pumps. Surely an electric combiboiler is a better alternative?

Swipe

Lapiz said:

If the government switched the green levy to gas electricity should be cheaper so why all the emphasis on expensive heat pumps. Surely an electric combiboiler is a better alternative?

Switching the levy from gas to electric would only decrease it by 23%. Also,  an electric combi boiler would use 3-4 times more electricity than a heat pump.

matelodave

The object is to use less energy, rather than reduce your heating costs.

An electric combi boiler is 100% efficient, so for every kwh that you put in you get 1kwh out, however a heat pump can be between 250 to 400% "efficient" insofar as you put 1kwh of leccy in but can get between 2.5-4kwh out.

It's still more expensive than mains gas and will remain so unless they really do bump up the price of gas to aroun 8-10p/kwh which would probably bankrupt most people and as in most things affect the less well disproportionately, most of whom still use gas.

Spies

wittynamegoeshere said:

We've got an instant electric water heater for the bathroom that's a long way from the hot water tank.  It's very difficult to work out whether it's worth heating more water than you need more efficiently instead of heating only what you need less efficiently.  There isn't a simple answer and it depends on your usage.

An electric-heated central heating boiler would be probably the worst possible heating system you could invent.  It would have absolutely no advantages over an electric oil-filled radiator in each room plus would have lots more complexity, noise and efficiency losses from all the wasted heat from the pipework.

A heat pump has some noise, complexity and wasted heat but that heat costs much less than simple electric heating.

My mother in law has electric central heating in the house she is renting, it costs her an absolute fortune!!

wittynamegoeshere

I'm surprised it even exists.  Why would anyone choose it?  I'm guessing shiny suits and carefully polished lies were probably involved.

We've got electric radiators but without plumbing, installed by the previous owners - there's an electric cable to each room, which each has a water-filled double radiator with a pump and element built into the gap in the middle.  It's definitely the worst of all worlds, all the noise and complexity of plumbing but with the expense of electricity.  The worst thing is that they butchered the existing plumbing beyond repair to fit this rubbish.

QrizB

Just in case anyone's wondering ...

The average UK dual-fuel house uses 12000kWh of gas a year, almost all for heat (CH & HW). Gas is currently around 4p/kWh and electricity is around 21p/kWh.

• 12000kWh of heat from gas via a 90% efficient boiler will cost £530.
• 12000kWh of heat from electricity via a 100% efficient boiler will cost £2520.
• 12000kWh of heat from electricity via a 300% efficient heat pump will cost £840.

wittynamegoeshere said:

I'm surprised it even exists.  Why would anyone choose it?

A mildly popular retrofit with landlords as it avoids all those gas safety issues, and the electricity bill is the tenant's problem.

worlestone

QrizB said:

Just in case anyone's wondering ...

The average UK dual-fuel house uses 12000kWh of gas a year, almost all for heat (CH & HW). Gas is currently around 4p/kWh and electricity is around 21p/kWh.

• 12000kWh of heat from gas via a 90% efficient boiler will cost £530.
• 12000kWh of heat from electricity via a 100% efficient boiler will cost £2520.
• 12000kWh of heat from electricity via a 300% efficient heat pump will cost £840.

wittynamegoeshere said:

I'm surprised it even exists.  Why would anyone choose it?

A mildly popular retrofit with landlords as it avoids all those gas safety issues, and the electricity bill is the tenant's problem.

That's helpful, thanks.  We're on E7 and looking to reduce energy usage and expenditure.  Current use is 14,200 pa with last years bills @ £1700. The ASHP quote we had estimated it's electric consumption @ 4500kWh, this was to heat the hot water.  My big concern would be the ability of an ASHP to heat the water enough, I though the max temp would be @ 45 degrees, not the 65 degrees we have currently, and therefore a risk of legionella (spelling?)

Verdigris

The pump should be programmed to increase the temperature of the hot water to 60 degrees, periodically, to kill off any bugs.

QrizB

worlestone said:

The ASHP quote we had estimated it's electric consumption @ 4500kWh, this was to heat the hot water.  My big concern would be the ability of an ASHP to heat the water enough, I though the max temp would be @ 45 degrees, not the 65 degrees we have currently, and therefore a risk of legionella (spelling?)

4500kWh should be enough to heat your whole house, not just the hot water.

Most ASHP controllers will raise the tank temperature to 65C every so often, for exactly that reason. If the ASHP itself can't get to that temperature it will instead kick in an immersion heater. That might sound expensive but if it needs eg. 5kWh to do it, once a fortnight, that's 130kWh for the year, roughly £22 worth.

Verdigris

QrizB said:

Most ASHP controllers will raise the tank temperature to 65C every so often, for exactly that reason. If the ASHP itself can't get to that temperature it will instead kick in an immersion heater. That might sound expensive but if it needs eg. 5kWh to do it, once a fortnight, that's 130kWh for the year, roughly £22 worth.

It won't be that much, I don't think, because the water will already be at 45 degrees, so not too much of a lift.

worlestone

QrizB said:

worlestone said:

The ASHP quote we had estimated it's electric consumption @ 4500kWh, this was to heat the hot water.  My big concern would be the ability of an ASHP to heat the water enough, I though the max temp would be @ 45 degrees, not the 65 degrees we have currently, and therefore a risk of legionella (spelling?)

4500kWh should be enough to heat your whole house, not just the hot water.

Yes, apologies, I should have been clearer, yes, to heat the whole house including the hot water