Heat Pump & Night Rate Meter - a no brainer?

BarneyMc · 08-02-2016 2:42pm #1

I'll be using an A2W HP and will soon be getting my electric connection. It is a no brainer to get a night rate meter to avail of cheaper night time electricity?

If using this meter daytime rates work out at about 20 cent during the day and 10cent at night. The standing charge is about €60 more than the standard meter. Full details are covered here.

I've looked around the market and a lot of providers have plans with rates at around 15 cent (all day and night). So, is it still a no brainer to get on the night rate meter or may it be just as good to get on one of the better plans coming in at 15 cent per KWh?

stickybookmark · 08-02-2016 4:28pm

Barney, do you really think an air to water will run efficiently at night time when temperatures of the air outside are cold?
GSHP running on night rate is a no-brainer. But A2W I'm really not sure.

To make night rate worth the higher day rate price that comes with night rate, you need one major item in your house (e.g. heating) to be running on it plus a few smaller items (Always turn washing machine and dishwasher on at night for example)

BarneyMc · 08-02-2016 7:41pm

stickybookmark wrote: »

Barney, do you really think an air to water will run efficiently at night time when temperatures of the air outside are cold?
GSHP running on night rate is a no-brainer. But A2W I'm really not sure.

Of course an A2W running at night will not run efficiently but that's not what I'm asking.

stickybookmark wrote: »

To make night rate worth the higher day rate price that comes with night rate, you need one major item in your house (e.g. heating) to be running on it plus a few smaller items (Always turn washing machine and dishwasher on at night for example)

That would be my A2W heat pump. :rolleyes:

ht9zni1gs28crp · 09-02-2016 10:43am

How long to make back that €60 in difference. Also what's your HW storage capacity like? What about when the UF calls for heat during the day?

stickybookmark · 09-02-2016 10:43am

BarneyMc wrote: »

Of course an A2W running at night will not run efficiently but that's not what I'm asking.

That would be my A2W heat pump. :rolleyes:

So why would you get night rate electricity if it's not efficient to run your heat pump at night time?

BarneyMc · 09-02-2016 12:10pm

stickybookmark wrote: »

So why would you get night rate electricity if it's not efficient to run your heat pump at night time?

Cheaper electricity unit rate.

BarneyMc · 09-02-2016 12:13pm

miller_63 wrote: »

How long to make back that €60 in difference. Also what's your HW storage capacity like? What about when the UF calls for heat during the day?

If it calls during the day then so be it. Although possible, I don't think it's practical to totally block the HP running during daytime rate hours.

stickybookmark · 09-02-2016 12:48pm

BarneyMc wrote: »

Cheaper electricity unit rate.

I visited a house (to see their polished concrete floor as it happens) and the owner was trying this (night rate with A2W) said it wasn't working out for him.

I'll be curious to see how you get on but I would be sceptial based on the principle of operation of A2W - taking heat from the air and transferring it to your heating system. And you want to do that chiefly at night when the air is cold? It just doesn't make sense to me on paper.

ht9zni1gs28crp · 09-02-2016 12:54pm

BarneyMc wrote: »

If it calls during the day then so be it. Although possible, I don't think it's practical to totally block the HP running during daytime rate hours.

But you really need to do the maths to make back that €60 going forward. As someone who lives with an A2W HP and seeing the difference in rates its probably not worth the hassle!

Also do you have any PV Panels going in?

JB81 · 09-02-2016 12:55pm

I have A2W and have it running only at night ( dual meter with night rate ), timed off during the day. Heats 300 Litre water tank at night too.
Temperature in the house is very nice all day and does begin to drop a small bit in the evening, but not enough to warrant me to boost heating. With the amount of insulation I have the heat is not escaping quick enough for me to need the heating on during the day ( most of the time ), however if temperature dropped to freezing outside for a continuous period ( ie: day and night like winter 2010/11 ) I would then boost it for a few hours in the afternoon.
Only other time pump is on during the day is if we need to top up hot water.
I definitely recommend night rate meter because, even though efficiency drops at night, I still maintain you save more than running heating during the day on standard rate without night meter.
Obviously if your insulation is not good, forget about A2W altogether!!

BarneyMc · 09-02-2016 1:56pm

stickybookmark wrote: »

I visited a house (to see their polished concrete floor as it happens) and the owner was trying this (night rate with A2W) said it wasn't working out for him.

I'll be curious to see how you get on but I would be sceptial based on the principle of operation of A2W - taking heat from the air and transferring it to your heating system. And you want to do that chiefly at night when the air is cold? It just doesn't make sense to me on paper.

At night the air is cooler but the electricity rate is cheaper. My questions is which wins out.

BarneyMc · 09-02-2016 1:59pm

miller_63 wrote: »

But you really need to do the maths to make back that €60 going forward. As someone who lives with an A2W HP and seeing the difference in rates its probably not worth the hassle!

Also do you have any PV Panels going in?

Yes, and that's why I posted the question - will a night rate meter save me money over a 12 month period? On the plus side it's cheaper electricity at night. On the down side it's more expensive daytime electricity, higher standing charges and less efficient HP functioning in the cooler air.

I would like to use PV in the future but no short term plans.

BarneyMc · 09-02-2016 2:03pm

JB81 wrote: »

I have A2W and have it running only at night ( dual meter with night rate ), timed off during the day. Heats 300 Litre water tank at night too.
Temperature in the house is very nice all day and does begin to drop a small bit in the evening, but not enough to warrant me to boost heating. With the amount of insulation I have the heat is not escaping quick enough for me to need the heating on during the day ( most of the time ), however if temperature dropped to freezing outside for a continuous period ( ie: day and night like winter 2010/11 ) I would then boost it for a few hours in the afternoon.
Only other time pump is on during the day is if we need to top up hot water.
I definitely recommend night rate meter because, even though efficiency drops at night, I still maintain you save more than running heating during the day on standard rate without night meter.
Obviously if your insulation is not good, forget about A2W altogether!!

Thanks for sharing a real experience. I have high levels of insulation and hope to have very good air tightness. Can I ask what floor you're using - sand/cement or liquid screed?

JB81 · 09-02-2016 4:29pm

75mm standard fine mix concrete floors

JB81 · 09-02-2016 4:29pm

BarneyMc wrote: »

Thanks for sharing a real experience. I have high levels of insulation and hope to have very good air tightness. Can I ask what floor you're using - sand/cement or liquid screed?

75mm standard fine mix concrete floors

BarneyMc · 12-02-2016 1:53pm

Would anyone else like to share their experience of how they use their HP and electric meter? I'm edging towards just using a standard meter and try to run the A2W HP during the daytime when temps are higher.

water-man · 12-02-2016 2:21pm

Hello,

Have a GSHP with UFH and HW - currently running night rate electricity. I'm only living in the house over 3 months so have only had one bill. It was Eur220 but it was an estimate.

My HP installer recommends running it during the day and not so much at night. I've discovered from my tinkering that I think he is right. If I run it at night the house is too warm for sleeping and then if it's off during the day it gets "cool" in the evening.

In saying this I plan to observe bills over the next few cycles before deciding if I should change meter as I run wash machine every night and dishwasher too.

WM

BarneyMc · 12-02-2016 5:01pm

water-man wrote: »

Hello,

Have a GSHP with UFH and HW - currently running night rate electricity. I'm only living in the house over 3 months so have only had one bill. It was Eur220 but it was an estimate.

My HP installer recommends running it during the day and not so much at night. I've discovered from my tinkering that I think he is right. If I run it at night the house is too warm for sleeping and then if it's off during the day it gets "cool" in the evening.

In saying this I plan to observe bills over the next few cycles before deciding if I should change meter as I run wash machine every night and dishwasher too.

WM

I'm a bit confused here. Are you currently on a night rate meter? I would have thought that for a GSHP it would be a no brainer to run it at night as the ground is not affected by night temperatures (well not near as much as air).

Also can I ask about your floors, liquid screed or sand/cement?

Metric Tensor · 12-02-2016 10:02pm

There are three competing issues here:

1. At what time your heat pump is most efficient.
2. At what time your electricity is cheapest.
3. How your floor screed (thermal store) behaves and when is best to heat it. This is often overlooked by people who are used to the rapid response (both in heating and cooling) of radiators. Most of us grew up with systems like this so it takes quite a change in mentality to adjust to a system with a slower (but more even) repsonse.*

*And of course the thickness and type of screed further complicate this matter.

BarneyMc · 13-02-2016 9:20am

Metric Tensor wrote: »

There are three competing issues here:

1. At what time your heat pump is most efficient.
2. At what time your electricity is cheapest.
3. How your floor screed (thermal store) behaves and when is best to heat it. This is often overlooked by people who are used to the rapid response (both in heating and cooling) of radiators. Most of us grew up with systems like this so it takes quite a change in mentality to adjust to a system with a slower (but more even) repsonse.*

*And of course the thickness and type of screed further complicate this matter.

Perhaps, to some extent, the nature of the outside walls affect this also? External walls that are not slabbed will regulate the inside temp much better whereas slabbed walls will lend themselves better to the "rapid response".

Metric Tensor · 13-02-2016 12:26pm

Yup. Spot on.

Any thermally dense materials inside the insulation envelope will increase the size of your thermal store this includes "non-slabbed" masonry on the inner leaf of external walls and also blockwork partition walls inside.

A bigger thermal store is slower to heat up initially but retains and releases the heat over a longer period thus evening out your thermal response. This, in my opinion, is very helpful in houses designed to stay at close to a constant temperature throughout the year (or the heating season anyway) - which is exactly what UFH/heat pump systems aim to do.

Curious Geroge · 13-02-2016 1:41pm

Danfoss 13Kw A2W setup. Night rate meter. Mon-Fri its off 8:30 to 5:30 and on auto otherwise. Have it set at 22 Deg which is comfortable. I had by default though to install a day (14c) / night (7c) meter but I question if its right as it would seem to be better to use the air during the day. Interested to hear more.

Also, anyone know if I can just switch to day rate or does the meter need to be changed out ?

BarneyMc · 13-02-2016 9:08pm

Curious Geroge wrote: »

Danfoss 13Kw A2W setup. Night rate meter. Mon-Fri its off 8:30 to 5:30 and on auto otherwise. Have it set at 22 Deg which is comfortable. I had by default though to install a day (14c) / night (7c) meter but I question if its right as it would seem to be better to use the air during the day. Interested to hear more.

Also, anyone know if I can just switch to day rate or does the meter need to be changed out ?

I assume 8:30 to 5:30 is daytime? I stand corrected on my first post and you're right, there's more than just one night rate provider and you've the best rate. I will be asking how much it would take to switch out the night rate meter early next week so will let you know if someone else here doesn't know. Interesting to hear that even on these favourable rates, you're thinking about flipping back to a regular meter.

daizy17 · 14-02-2016 2:47pm

stickybookmark wrote: »

I visited a house (to see their polished concrete floor as it happens)

I know its totally off topic but how was the polished concrete floor? We are very interested in this but havent seen many companies that do it. Have you found many and if so how were their prices.

Apologises thats its off topic.

stickybookmark · 17-02-2016 9:16am

water-man wrote: »

Hello,

Have a GSHP with UFH and HW - currently running night rate electricity. I'm only living in the house over 3 months so have only had one bill. It was Eur220 but it was an estimate.

My HP installer recommends running it during the day and not so much at night. I've discovered from my tinkering that I think he is right. If I run it at night the house is too warm for sleeping and then if it's off during the day it gets "cool" in the evening.

In saying this I plan to observe bills over the next few cycles before deciding if I should change meter as I run wash machine every night and dishwasher too.

WM

The system needs to be designed and set up at the installation stage to run on night rate. I'm dealing with 2 heat pump suppliers. One supports night rate the other doesn't. The one that supports night rate has thermostats in the house (which is divided into zones).

The one that doesn't support night rate their system runs off an external temperature sensor that kicks the heat pump on/off based on the external temperature and the temperature of the return fluid in the heating pipes.

In both cases if your bedroom is too warm for sleeping even if you don't have a thermostat in your bedroom where you can put in a set point of 18 for night time, you can control the amount of UF heating fluid going to your bedrooms via the manifold for the UF heating. Assuming your bedroom is one zone or all bedrooms are one zone, you just decrease the flowrate to that zone at the manifold til you get it where you want it.

GSHP and night rate is a no-brainer

stickybookmark · 17-02-2016 9:18am

daizy17 wrote: »

stickybookmark wrote: »

I visited a house (to see their polished concrete floor as it happens)

I know its totally off topic but how was the polished concrete floor? We are very interested in this but havent seen many companies that do it. Have you found many and if so how were their prices.

Apologises thats its off topic.

It looked amazing. We went to see that house as we were trying to choose between the limestone aggregate or the sandstone aggregate for our polished concrete floors. Sandstone has browns, reds, blues, greens in it, the limestone just has blues and greys.

We went for limestone in the end. You have to specify this to the concrete supplier before they come and pour your concrete obviously.

In terms of polishing it, the guy that's going to do it for us is charging 60 euro per square metre. Let me know if you want his details by PM.

Curious Geroge · 17-02-2016 6:14pm

stickybookmark wrote: »

The system needs to be designed and set up at the installation stage to run on night rate. I'm dealing with 2 heat pump suppliers. One supports night rate the other doesn't. The one that supports night rate has thermostats in the house (which is divided into zones).

I assume A2W systems since you mentioned the sensors. Can you PM the suppliers ?

stickybookmark · 18-02-2016 10:37am

Curious Geroge wrote: »

I assume A2W systems since you mentioned the sensors. Can you PM the suppliers ?

Both A2W and GSHP actually. We wanted GSHP, were corralled into A2W by our builders, now the builder has gone bust (we're at wall plate complete stage no roof on yet) and we're finishing off the house by direct labour so it's back to GSHP!

I will be running it on night rate. I'll PM you now

stickybookmark · 18-02-2016 10:40am

water-man wrote: »

In saying this I plan to observe bills over the next few cycles before deciding if I should change meter as I run wash machine every night and dishwasher too.

WM

Washing machine and dishwasher alone are not enough to justify the higher cost of day rate electricity that you are paying. You need to be running at least 30% of your total bill on night rate to justify it so you need one major item in your house (i.e. the heating) to be running on night rate. The washing machine and dishwasher just make up the numbers

BarneyMc · 18-02-2016 1:33pm

Curious Geroge wrote: »

Danfoss 13Kw A2W setup. Night rate meter. Mon-Fri its off 8:30 to 5:30 and on auto otherwise. Have it set at 22 Deg which is comfortable. I had by default though to install a day (14c) / night (7c) meter but I question if its right as it would seem to be better to use the air during the day. Interested to hear more.

Also, anyone know if I can just switch to day rate or does the meter need to be changed out ?

Just rang ESB Networks and it looks like I have to go with a dual tariff meter as this is what I requested in my initial application.

As soon as I'm connected (maybe next week) I plan on switching to another provider. Just off the phone with them and they said I can switch back to a standard meter for free but there will be a charge if I was to switch again.

So I'll go ahead with dual tariff for 12 months with provider x and then re-assess after that.

ht9zni1gs28crp · 18-02-2016 1:37pm

stickybookmark wrote: »

The system needs to be designed and set up at the installation stage to run on night rate. I'm dealing with 2 heat pump suppliers. One supports night rate the other doesn't. The one that supports night rate has thermostats in the house (which is divided into zones).

The one that doesn't support night rate their system runs off an external temperature sensor that kicks the heat pump on/off based on the external temperature and the temperature of the return fluid in the heating pipes.

In both cases if your bedroom is too warm for sleeping even if you don't have a thermostat in your bedroom where you can put in a set point of 18 for night time, you can control the amount of UF heating fluid going to your bedrooms via the manifold for the UF heating. Assuming your bedroom is one zone or all bedrooms are one zone, you just decrease the flowrate to that zone at the manifold til you get it where you want it.

GSHP and night rate is a no-brainer

This really doesn't make any sense at all, who is advising you on these two pumps and their system, yet more importantly the actual living with either of them?

Why on earth would you let your internal temp demands be governed by external temp after going to extremes to make your house airtight, insulated and cold bridge free as possible?

It sounds way more confusing than it needs be!

Heat Pump & Night Rate Meter - a no brainer?

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