Power consumption heat pump

[Deleted User]

Why can I not find a simple statement of input power consumption of a heat pump? All that I can see is sites such as https://www.viessmann.co.uk/heating-advice/Do-heat-pumps-use-a-lot-of-electricity which as clearly biased towards them with totally out of date prices for electricity (14p per unit)
They estimate £560 pa running cost - double this NOW
So hardly cheap

Verdigris

Gas has gone up by a commensurate amount.

You are asking "how long is a piece of string?". But in a properly set up system a heat pump will give 3 or more kWh of heat for every kWh of electricity in.

matelodave

The power consumption of a heat pump dpends on the input temperature of the external source (could be ground or air temperature) the flow temperature of the hot water (or output air ) and the amount of heat you are using. Much like a gas boiler, the more heat you require the more energy they consume, it's not a fixed amount.

ie on a cold day and the heating flogging its heart out then it could be quite a lot but much less when its not so cold and the house doesn't need as much heat. 

tacpot12

I've ended up reading the installation manual to find out this sort of information. The manual will usually include the size of the breaker needed for the pump which can also be useful in checking that you have enough capacity on your main fuse.

If a manufacturer makes their installation manuals hard to find, they don't deserve your custom. 

Verdigris

The maximum power consumption is easy enough to find. The machine will be listed as 6, 8, 12, or whatever kW.

matelodave

Not true, depending on the type of heatpump depends on it's power consumption, both at start-up and whilst it's running.

Mine for instance which is rated at 11kw, requires a 32 amp fuse (although it it has a soft start inverter driven compressor) but it's running power consumption is dependent on the input and output temperatures. It can be as low as around 120 watts but seldom goes above 4kw even when its flogging it heart out.  Today, it reheated our 200litre hot awter tank and consumed around 1.4kwh which is nothing like it's 11kw rating

Assuming it's got a COP of 3 them 11/3 = a consumption of 3.66kw/h although its more complex than that because it's got a variable speed drive which adjusts it's running current to suit the temperature uplift between input and output temps. It would have to attain a COP of 1 to use the same amount of power as it's output

Think of it a bit like a modulating gas boiler or even a gas hob - it only uses full power when its truned up to maximum, it uses a lot less when just simmering

Verdigris

I did say "maximum". The OP was asking an unanswerable question, going from power in to how much it costs.

QrizB

Deleted_User said:

Why can I not find a simple statement of input power consumption of a heat pump?

As everyone has said, the power consumption varies. For a 12kW heat pump producing its rated output, it might only draw 2.4kW when the weather's warm but 8kW when it's brass monkey time. See section 5.2 of this Panasonic pdf for examples.

What exactly are you trying to work out?

Keu

said:

Why can I not find a simple statement of input power consumption of a heat pump? 
They estimate £560 pa running cost - double this NOW
So hardly cheap

Do not bother with these, they are not fit for purpose, I have heard so many people on talk radio saying how useless they are. 

At least wait until the Gov gives you money as they promised they will do but do not expect the £5k in soundbite, that is for the toffs, the hoi polloi will be lucky to get £3k

matelodave

Keu said:

said:

Why can I not find a simple statement of input power consumption of a heat pump? 
They estimate £560 pa running cost - double this NOW
So hardly cheap

Do not bother with these, they are not fit for purpose, I have heard so many people on talk radio saying how useless they are. 

At least wait until the Gov gives you money as they promised they will do but do not expect the £5k in soundbite, that is for the toffs, the hoi polloi will be lucky to get £3k

perhaps if you actually had one and knew how to use it properly then you wouldn't be regurgitating hearsay.

They are fit for the purpose for what they were designed for but are often not used or installed properly.  What they aren't is a direct replacement for a  gas boiler and neither are they as cheap to run as a gas boiler but they do work and work well.

Effician

matelodave said:

perhaps if you actually had one and knew how to use it properly then you wouldn't be regurgitating hearsay.

I think here lies the problem with trying to roll this out to the masses, unlike the ealy adopters & avid tinkerers the average home user wants it as plug & play.