People Saying Heat Pumps are Rubbish - Are They?

Reed_Richards

grumpypensioner said:

Following my discussion with several local heat pump users, I add a further comment.

You seem to have been talking to some unfortunate and/or ill-advised heat pump users.

grumpypensioner said:

First a new build, installed a large ground source system. 

Ground source heat pumps are not suited to most properties and can be hugely expensive to install.  You should end up with a system that is a bit more efficient than an Air Source Heat Pump but at huge extra cost.  You used to get a really big government subsidy but not any more.

grumpypensioner said:

Under floor heating, very slow response and must be on continuously,

Yes, that's underfloor heating for you; nothing to do with your choice of heat source.  It would be just the same with a gas boiler.

grumpypensioner said:

heat pump system only reaches 40ºC), perma frost in back garden above heat exchangers. 

It sounds as if the heat exchangers were not buried as deep as they should have been so the system is not performing as efficiently as it should.

grumpypensioner said:

Yearly savings probably but no comparison with gas alternatives, huge cost outlay. 

This all supports my thinking that the heat exchangers were not installed properly.    

grumpypensioner said:

Performance ok as long as you don't open doors or windows.

I think you may have misunderstood.  If you want to build an energy efficient house you should make it as airtight as possible and for ventilation you use a forced-air heat exchange system that extracts heat from the outgoing air and uses it to heat the incoming air.  Your heating system should be specified to meet the needs of such a house.  If you start opening windows and doors you will cool the interior of your house much faster (in winter) and your heat pump may not have enough oomph to cope - because to do so it would have to be vastly over-specified for normal operation. 

Reed_Richards

grumpypensioner said:

Second user, installed an air source heat pump to heat the water,

You mean water for washing and for heating the radiators?

grumpypensioner said:

continuous operation with accompanying external fan noise (but directed at neighbours!). Back up emersion heater essential. 

It's impossible to heat a tank of hot water continuously unless you use hot water continuously so I assume what you are describing is a full heating system with radiators as well as a hot water cylinder?  Many heat pumps will heat the water in your cylinder to 50 to 55 C but you are supposed to heat it to 60 C once a week to guard against Legionella and it's common to use an immersion heater for that last 5 to 10 C up to 60 C.

zxzxzx

Again don't open doors or windows.

??

Would anyone run gas/oil heating with them open?

michaels

Surely you have to open the doors/windows for a decent length of time to cool the fabric of the building,  WE always have the little top light window in the bathroom open and could easily open the bedroom window for 5 mins to air out without losing a problematic amount of heat.

Reed_Richards

michaels said:

Surely you have to open the doors/windows for a decent length of time to cool the fabric of the building,  WE always have the little top light window in the bathroom open and could easily open the bedroom window for 5 mins to air out without losing a problematic amount of heat.

Exactly; opening doors and windows will cool the air inside the building and thence the fabric.  Whether the amount of heat you lose is problematic depends very much on the context.  If you live in a property that is decades old then the rate of air exchange is likely to be pretty high anyway so opening a window for a short while probably won't make that much difference to your total fuel consumption (and probably isn't strictly necessary).  If you live in a modern home that is well-insulated and made much more airtight then it will be much cheaper to heat and that amount of heat you lose by opening a window will be a significant amount of the heat you normally use.     

Spoonie_Turtle

QrizB said:

grumpypensioner said:

Following my discussion with several local heat pump users, I add a further comment.

Your accounts are entirely at odds with the three heat pump users I know, all of whom are entirely happy with their systems.

It's also at odds with our experience, which is not one of a knowledgeable person choosing to have a heat pump but having it foisted upon us and set up for comfort rather than efficiency (not at our request, we had no agency in any of the process).  We now have a warm home, a lot less mould, hot enough water still, and all for less electricity than we were using before.

grumpypensioner

Jolly good, obviously done their homework for their situation. Why not get them to leave descriptions of their circumstances to help others. Three down and the rest of the world to go.
My comments were based on the laws of physics and the Carnot cycle, and common sense. Not everything applies to everyone, but all follow natural laws. Apologies and sounds presumptious but it was my career and now age what done it!

matelodave

The general consensus is that a properly spec'd system, properly installed, commissioned and used correctly is efficient, will keep you warm and if you are lucky might save you money. But saving money depends on how you heated your home previously, the cost of leccy compared with what you used before and how much it costs to install it all in the first place.

When I got my system installed it replaced manky old storage heaters (we dont have mains gas), oil was expensive as was LPG and with a lot of scratching around we managed to get good electricity prices (although five of the suppliers went bust until it all fell apart).

Nowadays the per kwh cost of oil is around the same as mains gas but leccy is nearly four times the price so you need to achieve a SCOP of around four just to break even.

The problem is still the up front cost, so if you can get the system running with a SCOP of better than four then you need to do the sums to work out when you'll be in profit. I know you can install batteries and solar panels, but again you need to do a proper analysis to work out how long its  going take you to pay back, especially if you have to borrow money to pay for it all or lose interest or dividends on your capital.

I reckon I just about broke even a few years ago as we've now had our system for just under 15 years but I'm not sure that the SCOP of my system balances the cost of electricity versus oil or gas at the moment.

I dont feel inclined to splash out on solar or batteries at the moment as at 78 I doubt I'll live long enough to break even.

grumpypensioner

Best honest account I have yet read, I agree totally. Technology has much to offer, each current component version helps contribute but does not yet give a single complete solution. We need to blend "hybrid" approaches to achieve overall success of economy.
So don't just invest in one single large item of equipment, spread the load. I am personally impressed with my free standing air conditioner which rapidly heats/cools/dehumidifies my downstairs all for less than £500 capital outlay thus significantly reducing the load off my gas central heating system bills.
Would be good to hear other experiences?
Maybe of interest but I have had an Ecowitt Weather Station WS2910 in the garden wifi linked to an inside display and their cloud storage which provides me with historical data including outside and inside temperatures. Turned out to be very good at monitoring the result of my heating system in cold weather.

FreeBear

matelodave said: Nowadays the per kwh cost of oil is around the same as mains gas but leccy is nearly four times the price so you need to achieve a SCOP of around four just to break even.

But if you use a dedicated tariff aimed at heat pump users, the unit cost (for some of the day) should be quite a bit lower.