UPDATED: Air Source Heat Pumps/Air Con - Full Info & Guide, is it cheaper to run than mains gas?

Home_Farm wrote: »

We live in a rural area in the UK and recently installed an 18kW air source heat pump to switch from an oil boiler. So far it’s been great.

Glad to hear it - have you gone through a winter with it yet. Was the heating system upgraded or did you just bung the heatpump on in place of the old boiler.

fredwnelson wrote: »

Eon have informed me that the E18 tariff is being withdrawn. This currently enables me to run my ASHP system for 9.04 p per KwH. Does anybody have any advice as to which tariff or supplier to go for? The system runs 24/7 and uses 14000 kWh per annum

Hi

14MWh of energy to run a heat-pump equates to an average heating demand of around 5kWh on a 24*7*52 basis ... either you live in a mansion, there's little insulation, the heat-pump is constantly needing to use resistance based immersion backup or maybe you're looking at heat provision in kWh.t as opposed to electricity used?

... can you provide more info ....

HTH
Z

fredwnelson wrote: »

Apologies it is 6700 on heating and 14000 in total. The house is modern, energy rating B, has amazing insulation and also Solar for hot water

Hi

So that's a space heat demand of upwards of 20000kWh/year in a modern house with 'amazing insulation' plus an additional 7300kWh of general electricity demand ?? .... and above that it's also got the benefit of solar thermal ??

A modern large(ish) well insulated property would likely have a space heating demand approaching half of that figure, additionally, most would also be consuming around half of the additional electricity before taking steps to improve efficiency (LED TV, lights etc!) ....

For comparison .... our property is around 3x average in size, has PV, solar thermal, small heat-pump, log burner & GCH for deep winter heat top-up / DHW backup with all of this supported by insulation levels far beyond the minimum required by regulations .... we average around 10% of that total level of electricity purchases plus an additional approx 1000kWh of gas and somewhere around 2000kWh of logs for direct space heating, so it looks like they're plenty of scope available to reduce 14MWh of electricity purchases if you're prepared to look for it! ....

Anyway, regarding the tariff, have a look at least one of the price comparison sites, they should provide sole leads to what you're looking for.


HTH
Z

Thanks for the responses. The ASHP is a Daikin Altherma 11Kw installed in 2013. Everything I have read says to leave the unit switched on 24/7 and manage through room stats which we do. We keep them at 18C. We also have a woodturner which we only use very occasionally on very very cold days

Cardew wrote: »

You appear to be assuming that the System COP of fredwnelson's ASHP is well over 3.0. If you look at the any of the independant trials of ASHPs only a few achieve a COP of 3.0.


The requirement for an ASHP to run 24/7, or at least very long hours, means it compares unfavourably with conventional gas/oil CH systems in terms of overall heat requirement.

Most people with gas/oil CH shut off, or turn down the thermostat, overnight or when they are out during the day. With the high water temperature available it will quickly bring the house up to the required temperature.

The low water temperature of an ASHP means it has to run much longer hours producing heat that is not required at night or when occupants are out during the day.

Hi

If the HP is being run with UFH and at low temperatures then there's no real reason why it couldn't achieve a COP of 3.0 or more, most of the issues I've seen seem to be linked to running the system on a heating pattern similar to that you mention as if it were a much larger capacity GCH system and therefore reducing overall efficiencies ....

Regarding the heating at night .... you may have noted that the issue is that the question revolves around the system being able to consume low tariff energy, which may mean that the OP wants to do that very thing ... charging up the thermal mass of the property overnight and effectively using the structure as a storage heater throughout the day .... this is essentially the reverse of what we do for much of the year in using PV generation to run the HP to 'charge up' the thermal mass during the day and have little/no need for heat provision overnight! ...

HTH
Z