Hi Chris, welcome to the forum.

It is not quite as you state. If, as you have said, you require 12000kWh of energy for heating and DHW, what you are missing from your calculation is that an ASHP is approximately 300% efficient, so for every 1kWh you put in, you get 3kWh out.

So redoing your calculation would give 12000 / 3 = 4000kWh. The present cost of electricity in the UK is 34p/kWh, which would give an overall cost of £1360. Since you have solar PV, then some of the 4000kWh would be supplied free of charge from the Sun.

Of course you would have to pay for the installation of the heat pump.

Hi

thankyou for replying.

the total heat demand for property 47500 kWh/yr 

they quoted actual cost of electricity at £4006 at 0.27p kwh(Heat pump kWh used) so at todays rate 0.51p kWh (15833 x0.51p=£8000

they said it is usually less than is actually quoted,but it’s just no where near viable.

I know with the present energy guarantee the kWh is around 0.34kwh,reduced from 0.52 kWh ,but how long will this last !

in today’s economic environment a don’t think the government can afford to keep this up.

Two points to mull over @chris

1: I could do with knowing whereabouts you are geographically. As GB tackles the growing energy crisis, we should be preparing to migrate to Locational Pricing. Ie the cost per kWh of electricity varies according to the abundance of renewable generation in your vicinity.

More properly this is called Nodal Pricing because the price variations occur due to the number/type of transformer (a Node) through which the electricity passes to reach you, as well as the cable distance.

2: In my rural area of Devon there are number of wood-pellet boilers in locations that have poor vehicular access. These are supplied by the lorry using a large-bore flexible hose to transfer the pellets into a hopper. The delivery vehicle uses compressed air to carry the pellets along the pipe.

@chris 

Much better to work in kWh and not £.

If your heat demand is really 47,500kWh per annum then this will apply (give or take) whatever the heat source.  At about 9kWh/litre (allowing for (in)efficiencies) for oil that's a bit over 5000 litres.

Or work back from your current oil use in litres to see how many kWh you use now.  £2250 @ 90p/litre is 2500 litres.  Something doesn't add up. 

Actually if you are using 47,500 kWh for heating and HW then 12,000 consumed is quite optimistic, implying a combined SCOP of around 4. That's on the high side. 

Hi

yes we use about 2500L of oil,we’re careful!,and we have two log burners,you buy the oil on the dips,but there gone at the moment.

@chris,

what I'm saying is 2500 litres is 25,000 kWh at the most. I'm not sure how your quotes came up with 47,500 kWh, unless they are using different room temps or you are only using your oil heating intermittently. You can use the log burners with an ASHP too, a lot of people do. 

@transparent 

hi thankyou for replying,I live in Cheshire ,Sandbach,I thought biomass could only blow 20m,we live in a courtyard so only got 2.33m clearance,although double garage  with oil boiler faces the main rd,have you got biomass.

The 20m limit for wood pellets being blown is due to an ENplus 1a guidance document. This indicates that pellets may become fragmented/damaged if blown over longer distances.

I've just checked online, and there are certainly companies who do blow beyond 20m... albeit they then don't offer the ENplus 1a guarantee.

The main downside of 'damaged' pellets is that the dust level is greater. Some boilers handle this better than others. Hoppers can have integral dust-traps to reduce the amount of wood-dust being fed into the combustion chamber.

Whilst I don't know the details of your site or the distance in question, it may well be an issue which can be overcome with a bit of ingenuity.

For example, I wonder about the possibility of a delivery vehicle blowing the pellets through its flexi-tube to an interim 'mini-hopper' from where they are lifted the next few metres by a conveyor belt or Archimedes Screw. 🤔 

@kev-m 

hi,yes we use it intermittently,we have a oil cooker to(does DHW ,and about 6 radiators,heats up in 1 hour)so if it’s cold that goes on,if its freezing the boiler goes on ,so lots of options,I assume the ashp calculations have to be done on the building,one company said a 18kw should do,another said two 12kw .

does a flow temperature of 50c really work in buildings with solid walls!!

Hi @chrislay - you're very welcome here.

First a question: When first investigating the installation of an ASHP, did you get an Energy Assessor to survey your house and calculate the required heat demand? The report would've cost around £400-£500 and the assessor would be operating under the PAS2035 standard. Does that ring any bells?

Next a hint at a possible solution: Your cost issue is compounded by the need to keep your two HPs running on standard-rate electricity. An alternative is to run the HPs from a storage battery. You can then look for a tariff which allows you to re-charge that battery during lower-cost time-slots. You can also use PV solar panels to charge the storage battery of course.

And now, may I suggest you dive into two topics which are currently 'live':

ASHP options for Mum living in Cambridgeshire has some very useful guidance from others with a wealth of experience

Electricity price predictions has been running for some time. If you click on the link, it will take you to a moment when I posted diagrams discussing how future Time-of-Use tariffs could/should operate to alleviate the current energy-crisis.