Seeking advice on disappointing heat pump experience

Alex_ST

Looking for some advice please on getting best out of green energy tech. 

Have recently installed Vaillant aroTherm 7kw (new larger rads). 4kw solar panels and 5.12kw battery. 

I am not seeing any reduction in costs over the 15 yr/o electric boiler it replaced. House is 25 y/o 2-bed detached bungalow in central Scotland with semi-decent insulation. 

ASHP SCOP is just under 3 according to the vaillant control panel, but my other electricity use has inexplicably doubled (from ~4kwh/day to 8). Are there elements of the heating system which aren’t accounted for by the Vaillant controls? Solar is east-facing and negligible benefit at this time of year.  

The heat pump is slightly oversized as I had new rad fitted in attic room for occasional use but I have now turned this rad off to see if it helps control costs. 

Given that I can no longer benefit from economy 7 rates for most of my electricity usage (my split was 85/15 off-peak, I can’t get a smart meter) it looks like my bills will be about the same as before I installed any of this new tech. This seems wrong?

Also I dislike having to have a fixed temp all the time “for efficiency”. House is too warm at night and too cold in the day (18 degrees). But I was told “not to fiddle”. 

I really cannot recommend these “eco” changes to anyone else (ugly & unslightly, highly disruptive, expensive, no discernible benefit) and will probably move to a property with GCH next year. 

matt_drummer

If you are using Vaillant control data you have to add energy used to energy created and then divide by the energy used to get the COP.

I suspect your COP is better than you think.

4kWh of electricity is not very much if you had an electric boiler before, it is barely enough to run any home without electric heating let alone one with an electric boiler.

How did you only use 4kWh a day?

Your Vaillant is potentially a fantastically efficient heat pump.

It sounds like it is probably way too big, they exceed their badges output.

However, heat pumps are only going to be efficient when replacing another system that was used to heat the house.

If you never had heating on much before, then installing a heat pump can't save you much as there is nothing much to save. and then, if you use the heat pump to actually heat your home when you didn't before, it will consume electricity and more than you used before if you never actually used any to heat your home!

If you only used 4kWh a day before you had the heat pump then I cannot understand why you did it?

There's nothing to save!

Basically, heat pumps work well for people who want to heat their homes all the time, they are not good as an occasional source of heat.

Netexporter

A couple of observations.

Switching the spare room radiator off probably won't save you anything as it will merely worsen the COP by reducing the amount of water circulating in the system and possibly lead to short cycling of the heat pump.

If you were only using 15% off-peak on E7 you'd be better off on a straight tariff. (I may have misunderstood - if it was the other way round then fair enough)

Why can't you have a smart meter?

QrizB

I might be completely wrong here, but I'm going to make a wild guess that you've now got an immersion heater in your hot water tank and this is doing all your HW heating, rather than your heat pump.

Try turning the immersion heater off.

matt_drummer

matelodave said:

Installing heaps of new tech wont automatically mean that you save money. In fact if you spend lots on the upfront costs then you may never save money. However A heatpmp should beat an electric boiler hands down in the efficiency and cost arena, an SCOP of three means its should be producing 300% more heat than your electric boiler for the same amount of electricity input

Is it that all this magic equipment was installed at highly advantageous discouts from the Scottish Government or did you research and evaluate what you need and how to use it before going out and taking the plunge.

A heatpump is not a direct replacement for a boiler (electric, gas or oil) and therefore need to be operated differently

I would respectfully suggest that if you put the effort into understanding how it all works and tweaking it to optimise its performance to suit your lifestyle then its possible that you can save money especially compared to an electric boiler which TBH is the most expensive way anyone can heat their place (short of burning £50 notes in a fireplace)

I cant understand why you've given up on your E7 tariff especially when you've got batteries that can be charged overnight at the cheap rate, you can heat water overnight at the cheap rate and use other stuff at the cheap rate.  How did your electric boiler cope with all this, or didn't you heat your place during the day. E7 probably isn't the best way to run a heatpump but neither does it suit an electric boiler

Yes, even at the worst imaginable COP it is always going to be better than an electric boiler.

Vaillants are really good, really efficient and a preferred choice by many including me!

The heat pump is not the problem here.

Alex_ST

matt_drummer said:

If you are using Vaillant control data you have to add energy used to energy created and then divide by the energy used to get the COP.

I suspect your COP is better than you think.

4kWh of electricity is not very much if you had an electric boiler before, it is barely enough to run any home without electric heating let alone one with an electric boiler.

How did you only use 4kWh a day?

Your Vaillant is potentially a fantastically efficient heat pump.

It sounds like it is probably way too big, they exceed their badges output.

However, heat pumps are only going to be efficient when replacing another system that was used to heat the house.

If you never had heating on much before, then installing a heat pump can't save you much as there is nothing much to save. and then, if you use the heat pump to actually heat your home when you didn't before, it will consume electricity and more than you used before if you never actually used any to heat your home!

If you only used 4kWh a day before you had the heat pump then I cannot understand why you did it?

There's nothing to save!

Basically, heat pumps work well for people who want to heat their homes all the time, they are not good as an occasional source of heat.

You misunderstand spectacularly. I clearly stated that 4kwh was my usage for everything *other* than heating & hot water. I also explained that I was using an electric boiler previously on an off peak tariff. It supplied at least the same temperature as I am currently (not) enjoying. The heat pump is on constantly. 

I have calculated the SCOP correctly. Whether the s/w is capturing it correctly is not something I can easily verify. 

Alex_ST

Netexporter said:

A couple of observations.

Switching the spare room radiator off probably won't save you anything as it will merely worsen the COP by reducing the amount of water circulating in the system and possibly lead to short cycling of the heat pump.

If you were only using 15% off-peak on E7 you'd be better off on a straight tariff. (I may have misunderstood - if it was the other way round then fair enough)

Why can't you have a smart meter?

It’s not a spare room it’s a loft space. The insulation is inadequate. Does this change the calculus or is it still best to heat an unoccupied space (seems v counterintuitive) ?

what is “short-cycling?”

85% off peak. 

Not sure why, just told I can’t have one. 

Alex_ST

QrizB said:

I might be completely wrong here, but I'm going to make a wild guess that you've now got an immersion heater in your hot water tank and this is doing all your HW heating, rather than your heat pump.

Try turning the immersion heater off.

The immersion heater is programmed to come on only once a week for the legionella cycle. I don’t think turning it off is a good idea. In any event, there’s no way it could supply my central heating as they are separate circuits. 

QrizB

Alex_ST said:

QrizB said:

I might be completely wrong here, but I'm going to make a wild guess that you've now got an immersion heater in your hot water tank and this is doing all your HW heating, rather than your heat pump.

Try turning the immersion heater off.

The immersion heater is programmed to come on only once a week for the legionella cycle. I don’t think turning it off is a good idea. In any event, there’s no way it could supply my central heating as they are separate circuits. 

OK then, we're going to need a bit more info to help you work out where the "extra" 4kWh/day is going.

First, where are you getting your numbers from? I can see how you know your daily energy use but how are you splitting out the HP power from everything else? Do you have a separate meter for the HP?

What circuits are connected to the not-HP leg of the supply? Is there anything that's switched "on" in your consumer unit that used to be switched off?

Alex_ST said:

Also I dislike having to have a fixed temp all the time “for efficiency”. House is too warm at night and too cold in the day (18 degrees). But I was told “not to fiddle”.

Yo should be able to programme a night-time set back temperature, and 18C in the daytime might seem cold (I run 18C / 14C with wet GCH, but I know other households like it warmer).

Too often installers tell householders not to fiddle but don't bother finding out their preferences beforehand, leaving unsuitable defaults. This could be you.

matt_drummer

Alex_ST said:

matt_drummer said:

If you are using Vaillant control data you have to add energy used to energy created and then divide by the energy used to get the COP.

I suspect your COP is better than you think.

4kWh of electricity is not very much if you had an electric boiler before, it is barely enough to run any home without electric heating let alone one with an electric boiler.

How did you only use 4kWh a day?

Your Vaillant is potentially a fantastically efficient heat pump.

It sounds like it is probably way too big, they exceed their badges output.

However, heat pumps are only going to be efficient when replacing another system that was used to heat the house.

If you never had heating on much before, then installing a heat pump can't save you much as there is nothing much to save. and then, if you use the heat pump to actually heat your home when you didn't before, it will consume electricity and more than you used before if you never actually used any to heat your home!

If you only used 4kWh a day before you had the heat pump then I cannot understand why you did it?

There's nothing to save!

Basically, heat pumps work well for people who want to heat their homes all the time, they are not good as an occasional source of heat.

You misunderstand spectacularly. I clearly stated that 4kwh was my usage for everything *other* than heating & hot water. I also explained that I was using an electric boiler previously on an off peak tariff. It supplied at least the same temperature as I am currently (not) enjoying. The heat pump is on constantly. 

I have calculated the SCOP correctly. Whether the s/w is capturing it correctly is not something I can easily verify. 

OK, great.

My help has finished then.

Alex_ST

Seems to be a lot of confusion/disbelief about this experience. I accept that it is UNEXPECTED—hence this thread. 

From my research this certainly *should* have been a more affordable solution. From my experience, it *is not*. 

The disbelief is frankly, absurd. 

There are all sorts of things that might have gone wrong here. The design, the installation, the components, the monitoring system, the operation and probably many things I haven’t considered as a novice. 

I understood my simple old system inside out and had it running efficiently (economically on a par with a gas boiler, YES REALLY!) 

I don’t have any experience with this new system and don’t have any interest in researching it exhaustively and micromanaging every kWh—no disrespect if that’s your hobby, but it just sounds like work to me. I just want to check the most likely things to have gone wrong in this installation before I get someone in to investigate.