Big Four - Solar, Battery, heat pump and EV

[funduffer]

Well, if we are to go all electric, we might as well go all in! That is, operate the 'big four' - solar, battery, heat pump and EV.

I have solar and an EV already, and very happy with both. I use gas for heating currently and the combi Vaillant boiler is approaching 10 years old. So looking to replace this with a heat pump and battery.

I am considering getting an air-source heat pump + hot water tank, and a 10kWh battery. I have a heat pump + tank quote for <£3000 (taking into account the £7500 subsidy) and I assume a 10kWh battery is around £3000 also. so, about £6k all in.

My usage plan would be to charge the EV and battery, and heat the hot water, during off-peak night hours (6 hours @7.5p per kWh). Then, run the battery during peak times, along with any solar, to run the house, including the heat pump for home heating. Based on my actual gas and electricity usage over the last 2 years, and taking account of different seasonal usage, I estimate that I will save over £600 per year in fuel bills, and payback will be within 9 years (ignoring the cost of a replacement gas boiler, which would reduce payback to 4.5 years).

My main concern is finding a controller with the flexibility to do what I want. I need to control when I charge and discharge the battery, when I use battery, solar and grid energy, and when I export excess power to the grid from solar and/or battery.

I have a myenergi Zappi EV charger, and their Libbi battery and controller look pretty good, but they have nothing about heat pumps. Maybe that doesn't matter?

My electricity supplier is Octopus (Intelligent Octopus Go tariff), and they might have something that can control the Big Four, but I am not sure if I want their 'high temperature' Cosy heat pump. I think I would prefer a class leading heat pump from someone like Vaillant, Daikin or Mitsubishi.

Has anyone experience of the 'Big Four', and what they use for controlling this sort of home energy system? Should I go for proprietary or third party?

FD

[DrFfybes]

I have solar and an EV already, and very happy with both. I use gas for heating currently and the combi Vaillant boiler is approaching 10 years old.
[...]
I am considering getting an air-source heat pump + hot water tank, and a 10kWh battery. I have a heat pump + tank quote for <£3000 (taking into account the £7500 subsidy) and I assume a 10kWh battery is around £3000 also. so, about £6k all in.

I applaud your commitment - not sure I'd be ditching a 10 year old Big Brand boiler just yet. However if you do then I think you are wise to go for a known brand in the field.

I think your battery cost estimate is a bit low - you will need a battery, battery management system, and a way of connecting it into the inverter. If you are with Octopus the Givenergy all-in-one is 13.5hWh and all the bits and will just plug into your existing setup, and is compatible with the Octopus smart flux tariff where they charge it often for free and discharge when it benefits you(!) most.

However do you NEED to buy another battery, when you'll have one about 5 times the size parked outside during your peak consumption periods?

Paul

[funduffer]

I think your battery cost estimate is a bit low - you will need a battery, battery management system, and a way of connecting it into the inverter. If you are with Octopus the Givenergy all-in-one is 13.5hWh and all the bits and will just plug into your existing setup, and is compatible with the Octopus smart flux tariff where they charge it often for free and discharge when it benefits you(!) most.

However do you NEED to buy another battery, when you'll have one about 5 times the size parked outside during your peak consumption periods?

Paul

Unfortunately the EV is over 2 years old and cannot export power, although it does have a 64kWh battery, as you guessed.

I think I will get a battery connected on the AC side with its own inverter, as I want to be able to charge it from the grid and export to the grid. Presumably that is what the Octopus / Givenergy one does? I shall look into it.

FD

[servodude]

I think your battery cost estimate is a bit low - you will need a battery, battery management system, and a way of connecting it into the inverter. If you are with Octopus the Givenergy all-in-one is 13.5hWh and all the bits and will just plug into your existing setup, and is compatible with the Octopus smart flux tariff where they charge it often for free and discharge when it benefits you(!) most.

However do you NEED to buy another battery, when you'll have one about 5 times the size parked outside during your peak consumption periods?

Paul

Unfortunately the EV is over 2 years old and cannot export power, although it does have a 64kWh battery, as you guessed.

I think I will get a battery connected on the AC side with its own inverter, as I want to be able to charge it from the grid and export to the grid. Presumably that is what the Octopus / Givenergy one does? I shall look into it.

FD

are you located in a place where you can go all Douglas Adams and have evac-tube solar water as the 5th of your big four?

[Gerry557]

Why get rid of your Valient boiler whist it's still working fine and likely to do so for some time yet. Use the time to await better and cheaper technologies.

[funduffer]

Why get rid of your Valient boiler whist it's still working fine and likely to do so for some time yet. Use the time to await better and cheaper technologies.

With a £7500 subsidy on offer, the current ‘expensive’ new technology is actually pretty cheap - I.e. roughly the same as the old technology!

Also now there is no VAT on batteries.

The heat pump is hardly new technology, it has been around for years, except now it has been improved to achieve very high efficiency levels.

I think the time is right to consider the move.

FD

[SMarkus]

Hi Funduffer. We have the big four - briefly, we have a 5 bed Victorian house, with 16kWh Daikin air source heat pump, Tesla M3, 3.4kWh solar panels and a 27kWh battery storage. We use Intelligent Octopus and our bills are just under £100 a month over the course of a year. Without Intelligent Octopus and the batteries/panels, bills would be in excess of £3k/yr. Heating is on 24 hrs/day, using a weather dependent curve, and we have a hot water cylinder (250l) as well, so very similar to what you're proposing. The heat pump works very well for us despite many poo-pooing the idea and although we have good double glazing, we've not done a lot else to retro-fit the house.

In terms of control, it is possible to set the battery to charge on a regular schedule overnight on the cheap tariff, and this works very well. Usually the car charges overnight as well. Things become complex once charges take place during the day, as we don't want to deplete the battery. To coordinate all this, and understand better what the solar produces and what we use, I have started to implement Home Assistant - this is an open source home automation system with a large number of third party integrations available.

So in a scenario where Octopus are kind enough to give me some charging slots outside the 11:30 - 05:30 period, I would use Home Assistant to check the state of the battery, if necessary then add some charge to it whilst on the cheap tariff, and then set it to not discharge whilst the car is being charged. The heat pump can also be integrated, at least up to a point, although direct control does not seem to be available at the moment.

If you already have an EV and solar, then I would recommend you go the extra distance and go fully electric - even on standard tariffs, there is no real extra cost to using a heat pump, and with the advantage of cheap tariffs for EVs, it can be very cost effective indeed.

Hope that helps,
Steve.

[funduffer]

In terms of control, it is possible to set the battery to charge on a regular schedule overnight on the cheap tariff, and this works very well. Usually the car charges overnight as well. Things become complex once charges take place during the day, as we don't want to deplete the battery. To coordinate all this, and understand better what the solar produces and what we use, I have started to implement Home Assistant - this is an open source home automation system with a large number of third party integrations available.

So in a scenario where Octopus are kind enough to give me some charging slots outside the 11:30 - 05:30 period, I would use Home Assistant to check the state of the battery, if necessary then add some charge to it whilst on the cheap tariff, and then set it to not discharge whilst the car is being charged. The heat pump can also be integrated, at least up to a point, although direct control does not seem to be available at the moment.


Steve.

Thank you Steve for your helpful comments - it looks like my thinking is on the right lines.

I shall have a look at Home Assistant, as it sounds like what I am looking for and your real world experience is helpful.

I have 4.225kW of solar and a 64kWh Kia Niro. I have heavily insulated the house and recently got an EPC B rating, so I think the heat pump I get will be more like 7kW, and a 10kWh battery should suffice. Shame the Kia can't export to the house, but I love the EV and the almost 300m range.

I have estimated my monthly fuel bill, based on current unit rates, as £70 per month, which sounds about right for a 3 bed bungalow against your bigger property. I am currently paying £130, using Intelligent Octopus and their standard Gas tariff.

FD

[Mike4]

The heat pump is hardly new technology, it has been around for years, except now it has been improved to achieve very high efficiency levels.

But with a flow temperature of only 35c (or so I've just been advised), the high efficiency is best achieved using underfloor heating. Radiators just don't cut it, apparently.

Just reporting contents of a convo over in the Combustion Chamber. It may or may not be correct but well worth checking out before going too far down the ASHP route.

[Hallucigenia]

But with a flow temperature of only 35c (or so I've just been advised), the high efficiency is best achieved using underfloor heating. Radiators just don't cut it, apparently.

Except modern high-temperature heat pumps can easily match the flow temperatures of boilers, so if you have radiators that work with a boiler, they will work with a HT heat pump.

[Mike4]

But with a flow temperature of only 35c (or so I've just been advised), the high efficiency is best achieved using underfloor heating. Radiators just don't cut it, apparently.

Except modern high-temperature heat pumps can easily match the flow temperatures of boilers, so if you have radiators that work with a boiler, they will work with a HT heat pump.

That's pretty much what I thought too but I've been advised otherwise. Possibly, the HT heat pumps so far are all by firms no-one has ever heard of, leading to potential technical support problems like those being discussed in the Dimplex heat pump thread.

[BullDog]

Except modern high-temperature heat pumps can easily match the flow temperatures of boilers, so if you have radiators that work with a boiler, they will work with a HT heat pump.

That's pretty much what I thought too but I've been advised otherwise. Possibly, the HT heat pumps so far are all by firms no-one has ever heard of, leading to potential technical support problems like those being discussed in the Dimplex heat pump thread.

I looked last week at Mitsubishi "high temperature heat pumps" after a glowing advertorial in last week's Times. Be careful. The heat pump is indeed capable of delivering water temperature akin to a gas boiler. Around 70 Celsius. However, the CoP numbers published only go up to 55 Celsius. The often quoted impressive CoP number it turns out is for a temperature of just 35 Celsius. CoP isn't even quoted for temperatures more than 55 Celsius. Funny thing that. I am thinking a CoP of about 2 or maybe less is likely when delivering water at 70 Celsius. I am also thinking the design life quoted by Mitsubishi of 10 years will also probably be less running at 70 versus 35 Celsius. There's no such thing as a free lunch in thermodynamics. Or anything else for that matter.

On the upside, the Mitsubishi units appear to be made in the UK. No doubt assembled from Asian components. I suppose you can't have everything.

In a nutshell, it seems yes, high temperature heat pumps are a thing. But they're far from perfect. In the glowing advertorial the heat pump was being used to replace an old oil boiler in an annexe.

(Some folks might also be interested in hearing about the hot water storage tank that looked about 2.5 metres tall and pretty much needed it's own room with it's auxiliaries. But that's another part of the story really).

[Hallucigenia]

I looked last week at Mitsubishi "high temperature heat pumps" after a glowing advertorial in last week's Times. Be careful. The heat pump is indeed capable of delivering water temperature akin to a gas boiler. Around 70 Celsius. However, the CoP numbers published only go up to 55 Celsius. The often quoted impressive CoP number it turns out is for a temperature of just 35 Celsius. CoP isn't even quoted for temperatures more than 55 Celsius. Funny thing that. I am thinking a CoP of about 2 or maybe less is likely when delivering water at 70 Celsius. I am also thinking the design life quoted by Mitsubishi of 10 years will also probably be less running at 70 versus 35 Celsius.

Except in the real world, high-temperature heat pumps run so rarely at high temperatures that their CoP isn't that different to "regular" heat pumps :

https://es.catapult.org.uk/news/heat-pu ... s-boilers/

The median SPF observed in ASHP systems during the EoH Demonstration Project was 2.80 (280%)*. This is a significant increase of around 0.3 to 0.4 (30-40%) since the Renewable Heat Premium Payment scheme (RHPP) heat pump trial was undertaken between 2011-2014....

The EoH Demonstration Project analysed the performance of heat pumps on some of the country’s coldest days (where mean daily temperatures fell to as low as -6oC) and found only a marginal decline in whole system performance. The median ASHP system efficiency was 2.44 (or 244%) on the coldest days of the year...

the High Temperature ASHPs used in the Project have performed with similar efficiencies to Low Temperature ASHPs. Heat pumps are controlled to only demand higher temperatures when it’s colder outside. During the project, these weather compensation controls rarely demanded higher temperatures, allowing the units to maintain good heat pump efficiencies whilst keeping a wider variety of properties warm year-round.

[BullDog]

I looked last week at Mitsubishi "high temperature heat pumps" after a glowing advertorial in last week's Times. Be careful. The heat pump is indeed capable of delivering water temperature akin to a gas boiler. Around 70 Celsius. However, the CoP numbers published only go up to 55 Celsius. The often quoted impressive CoP number it turns out is for a temperature of just 35 Celsius. CoP isn't even quoted for temperatures more than 55 Celsius. Funny thing that. I am thinking a CoP of about 2 or maybe less is likely when delivering water at 70 Celsius. I am also thinking the design life quoted by Mitsubishi of 10 years will also probably be less running at 70 versus 35 Celsius.

Except in the real world, high-temperature heat pumps run so rarely at high temperatures that their CoP isn't that different to "regular" heat pumps :

https://es.catapult.org.uk/news/heat-pu ... s-boilers/

The median SPF observed in ASHP systems during the EoH Demonstration Project was 2.80 (280%)*. This is a significant increase of around 0.3 to 0.4 (30-40%) since the Renewable Heat Premium Payment scheme (RHPP) heat pump trial was undertaken between 2011-2014....

The EoH Demonstration Project analysed the performance of heat pumps on some of the country’s coldest days (where mean daily temperatures fell to as low as -6oC) and found only a marginal decline in whole system performance. The median ASHP system efficiency was 2.44 (or 244%) on the coldest days of the year...

the High Temperature ASHPs used in the Project have performed with similar efficiencies to Low Temperature ASHPs. Heat pumps are controlled to only demand higher temperatures when it’s colder outside. During the project, these weather compensation controls rarely demanded higher temperatures, allowing the units to maintain good heat pump efficiencies whilst keeping a wider variety of properties warm year-round.

Thanks. Which of course is absolutely fine. But our house doesn't get warm enough when circulating water much below 70 Celsius.

[DrFfybes]

Thanks. Which of course is absolutely fine. But our house doesn't get warm enough when circulating water much below 70 Celsius.

I turned out boiler down to 55C and it struggled in the cold snap, so it went back to 65C. But this is a poory insulated 230 year old place, now we're replacing the roof and installing some insulation I expect that to change dramatically. I would hope most houses built in the last 20 years could cope with a lower flow temp, and TBH with larger rads we probably could too.

Out of interest how old are your rads? - in my Brighton flat we were freezing the first winter until a plumber mate looked at the rads, alughed, and swapped them all for slightly larger type 22s.

Paul

[BullDog]

Thanks. Which of course is absolutely fine. But our house doesn't get warm enough when circulating water much below 70 Celsius.

I turned out boiler down to 55C and it struggled in the cold snap, so it went back to 65C. But this is a poory insulated 230 year old place, now we're replacing the roof and installing some insulation I expect that to change dramatically. I would hope most houses built in the last 20 years could cope with a lower flow temp, and TBH with larger rads we probably could too.

Out of interest how old are your rads? - in my Brighton flat we were freezing the first winter until a plumber mate looked at the rads, alughed, and swapped them all for slightly larger type 22s.

Paul

30+ years old. I have replaced some and the increased heat output of old v new radiators is noticeable.

The other issue related to lower flow temperature is that on the Y plan system that we have, the domestic hot water doesn't really get hot enough unless the boiler flow temperature is above 65 Celsius.

[9873210]

Except in the real world, high-temperature heat pumps run so rarely at high temperatures that their CoP isn't that different to "regular" heat pumps :

the High Temperature ASHPs used in the Project have performed with similar efficiencies to Low Temperature ASHPs. Heat pumps are controlled to only demand higher temperatures when it’s colder outside. During the project, these weather compensation controls rarely demanded higher temperatures, allowing the units to maintain good heat pump efficiencies whilst keeping a wider variety of properties warm year-round. [/i]

In the real world almost all heating systems are misconfigured.

People notice that the heating system is not up to snuff on the coldest day of the year and turn off the modulation. Or they notice that the heater is running at 100% duty cycle (as designed), think "that can't be right" and start twisting knobs. People use timers etc, in ways that defeat thermostats. Output temperature should not be a user or technician settable parameter. Maximum temperature, maybe, but the operating temperature should be determined by the controls on the basis of demand. If you need hotter water to defeat legionella, use a timer to do that for a couple of hours a fortnight don't set a permanent high temperature.

Thanks. Which of course is absolutely fine. But our house doesn't get warm enough when circulating water much below 70 Celsius.

If it can get the house warm enough on the coldest day of the year at 70C it can get the house warm enough the other 364 days at a lower temperature. What you need is a properly trained technician and a properly trained dog. The technician should properly configure the system. The dog should bite anyone tries to reconfigure the system.

[Mike4]

A brief Goggle revealed that Octopus are flogging HT heat pumps. So I asked for a quotation.

I filled in a few details on a web page such as my name, postcode and house number, type of house and whether I owned it. And bingo, in about four seconds flat it gave me a quote of £12.506.49, or £5,006.49 with the guvvermint grant. No VAT.

I was impressed that they were able quote to fractions of a quid!

https://octopus.energy/get-a-heat-pump/

[BullDog]

A brief Goggle revealed that Octopus are flogging HT heat pumps. So I asked for a quotation.

I filled in a few details on a web page such as my name, postcode and house number, type of house and whether I owned it. And bingo, in about four seconds flat it gave me a quote of £12.506.49, or £5,006.49 with the guvvermint grant. No VAT.

I was impressed that they were able quote to fractions of a quid!

https://octopus.energy/get-a-heat-pump/

LOL! I have just tried twice and the web page crashed both times!

[Mike4]

A brief Goggle revealed that Octopus are flogging HT heat pumps. So I asked for a quotation.

I filled in a few details on a web page such as my name, postcode and house number, type of house and whether I owned it. And bingo, in about four seconds flat it gave me a quote of £12.506.49, or £5,006.49 with the guvvermint grant. No VAT.

I was impressed that they were able quote to fractions of a quid!

https://octopus.energy/get-a-heat-pump/

LOL! I have just tried twice and the web page crashed both times!

Ah, I had that too on my first attempt. There is a box on the RHS of another box that I'd overlooked and failed to fill in. Crashes the page according to a message that displays.

Other boxes missed bring up a different message telling you.