@editor Top Class forum indeed! I wanted to have an Octopus Energy install (see elsewhere) but was far too non-standard for their limited offerings over a year ago. Best wishes for your future project and enjoy the journey. Regards, Toodles

Hi @declan90 - we'll be very happy to discuss those options with you.

On this forum we usually segregate the various technologies into separate topics. But you may wish to consider an integrated approach, whereby solar-panels fill your (off-grid) battery, which then runs your heat-pump. At this stage in your thinking, I assume that all options are still on the table.

A lot depends on how much you would like to implement on a DIY basis as opposed to hiring a professional. Have a look at my comments about self-installing storage batteries on this topic a week ago.

Sometimes you need to use a professional installer in order to obtain a government grant/subsidy.
The better-known examples are a heat-pump or when you want your PV panels to export to the grid.
But this may not necessarily be the most efficient strategy in the longer term.

Perhaps you could give us an idea of

• the size of your home in square metres
• the current status of its insulation (the EPC rating is a good start), or the total heat-loss figure which you got from that Octopus survey
• how much you'd like to attempt yourself, assuming we gave you the technical guidance and where to find suppliers
• your approximate geographical area; your electricity region would suffice
• the orientation of the roof, to assess its use for solar panels

@declan90 Hi Declan. On the face of it, it sounds like your granny annex might be a good contender for an air to air heat pump. relatively inexpensive, quick to warm a room from cold and with the bonus of cooling on hot days.

@transparent modern solar hotwater equipment as you have highlighted is more effective and may produce 60C hotwater in December / January.

My assumptions are simply based on experience with this equipment I have installed which is 25+ years old. Sadly the manifold will be lucky to reach 35C in December / January and no useable hot water is generated between October to April and only assists the boiler with up to 45C on average (definitely not hot enough on its own for the solar blending valve to regulate the temperature properly causing issues with the Missus bath temperature, enough said! lol ).

My plan is not to run hotwater production directly from PV panels but via cheap electricity during the night, the heat pump and a new storage battery when I get around to installing. I can then top up the battery during the day with PV's (when I get to fit them). The new tank that will be fitted in October will have a larger useable hotwater capacity in the Winter and hopefully be more efficient to heat (better insulation larger coils etc)

As mentioned earlier I have a number of maintenance tasks to be performed in my property on a regular basis and reducing that list is one of my goals. My solar system needs tending to regards replacing the glycol every twoish years and issues arising due to it coming to the end of its working life. I also have a solar blending valve in the system due to the extreme water temps in the summer 68C+ which sadly needs striping down and descaling once a year due to our hard water area.

I figured an all electric system, there would be less to do (if anything), it can do other things not just hot water plus no more trips onto the roof! 😀

@declan90 welcome to the forum.

I had a heat pump fitted about two months ago in a 1970's house which has a 1995 extension. All the rad's in the old part of the house are still the originals which are large as I believe in those days they oversized them by approx 50%  (which is good for ASHP) all connected with 15mm piping. My heating engineer did not see any problems regarding using them. He just replaced a rad in the kitchen but that was due to cosmetics and our new kitchen fit.

The essential task to be done is the heat loss calculations requiring all windows, rooms and insulation to be measured so the correct sized pump is fitted and has the capacity to provide the required heat to at least -10C outside temp. If your engineer cannot or does not know how to do these calculations then I suggest to steer clear and keep looking.

I would also ask to see previous ASHP work they have done and most good engineers are more than happy to show off their talents, I know mine is! lol

@transparent thank you - given the quality of advice I've already received here, I'll certainly do that!

Thanks for all the warm welcomes. @editor I think you’re right, best for me to start a specific thread relating to my ‘project’

@toodles – I believe it was indeed your posts I found that led me to believe I might get a computer says no response from Octopus. I’ll wait and see what response / answers I get from them. It would be a shame for them to rule it out after such a thorough survey, but I understand that they’re looking to drive costs down by generating throughput

@Transparent I’ll put a good description of what I’m looking at, and the thoughts/info I’ve already collated, into a separate thread as to not hijack this one. Unfortunately, I’m a little on the risk averse side for looking to do too much of this DIY – I think it might be a difficult enough job convincing my wife its all a good idea anyway. Definitely all (other) options on the table. Interested in conversations (similar to those I’ve seen elsewhere on here) into solar PV driving immersion in summer vs use of HP (pro’s and con’s of potentially being able to turn off the ASHP and any pumps over the summer months). Also ROI vs tariff chasing on installing sufficient batteries to cover peak hours load in winter.

@bontwoody as the annex is potentially going to see use as an office the ability to have cooling too might be attractive. My two main reasons for trying to combine all my heating requirements into a single solution are 1) Planning; there is a limit for 1 HP under PD, where do air to air units sit within this? (obviously don’t have as big an outside presence) 2) the annex has a bathroom / shower room and while I think it’s consumer unit would take it, I’m loathed to potentially end up with an electric shower if I can avoid it.

@Technogeek I’m glad to hear that your rads / CH plumbing didn’t require extensive modifications. My situation sounds very similar, looks to be 15 mm piping to all rads with larger pipework closer to the boiler. Just a shame I hadn’t thought to have more of a nosey how far the 22mm / 28mm pipework goes when the landing floor was up for some electric works ~6 months ago. But it looks like the installer did a good job of oversizing in many areas

@transparent Hope your good? Hoping the following will be of interest to you and other readers

To conclude this solar tube topic I decided for our particular application, from a financial perspective, the solar system is not cost effective hence the decision to de-commission.
Solar tubes are efficient as you have demonstrated and will probably be good in the scenario of hot water being drawn off regularly during the day (public place for example) or heating large volumes of water e.g swimming pools.

Our particular lifestyle is as follows:

We are at work all day so no hot water is drawn until the evening most days.
The wife has baths in the Winter when our solar system produces the least
We have showers in the summer when we use hot water the least but production is at its maximum

Currently our electric tariff is 31p / Kwh daytime and 9.5p / Kwh for 4 hours in the night

In the past, to heat the same volume of water in the tank using the boiler, it uses 1.1 litres of oil (metered reading) or 70p (slightly cheaper with ASHP) at the price I paid minus the cost of running a 70w solar pump for an average of 10 hours gives a net saving of 70p - (0.7 Kwh x 31p) = 49p per day.
If the solar system heated our hot water 365 days a year it would provide a saving of £178 per year but that sadly will never be acheived

Excluding the EV and ASHP consumption our current electricity useage is on average 7Kwh per day
To install a home battery as a minimum and purchase 7Kwh during the night would cost us 9.5p x 7Kwh = 66.5p or £242.73 a year.
The cost using the same power throught the day would be 31p x 7kwh = £2.17 or £792.05 a year.

So using a simple battery system can potentially save us £792.05 - £242.73 = £549.32 per year compared to the solar system saving of a maximum £178 per year.
In addition I have signed up to our local PowerUp scheme (a trial at the moment in this area) which means you are paid to use electricity (at random times), so I could charge the battery and have free electric all day, happy days!

Saving with the battery system £549+ per year (in our case worth it)
Saving with solar tube system, max £178 per year but realistically 60% of this ( in our case not worth it)

The savings from a battery system in our case can then be used to help with the running costs of the ASHP (the EV is covered by work mileage payments so excluded)

Hopefully that has helped explain my perspective and my decision in our case that solar tubes are not for us 🙂

Thanks for that arithmatic @technogeek and I hope newcomers here can follow that example.

Your electricity tariff tells us that you're currently using Octopus Go.

Posted by: @technogeek

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In addition I have signed up to our local PowerUp scheme (a trial at the moment in this area) which means you are paid to use electricity (at random times)

Can you expand on that scheme (remembering that this is the welcome topic, so no great depth please!)

Is that PowerUp scheme also instigated by Octopus, or is it a Community Energy trial?
How is the payment received?

Why is it at "random times"?

As you indicate that the trial is operating in a geographical area, let me insert here the term Nodal Pricing (aka Locational Pricing).

This method of offering lower-cost electricity during times when there is surplus renewable generation is an important part of the Future Energy Strategy.
It's one of the topics in the Call for Evidence by the Parliamentary Committee on DESNZ (Dept Energy Security and Net Zero). Closing date 25th Aug... next week!

At the moment surplus electricity is discarded, using a mechanism called Active Network Management (ANM).
This is stipulated in the contract between an large energy supplier and the DNO when the grid connection is first applied for.

The supplier is given an ANM plot showing the times of day and days of the year when export to the grid is likely to be constrained.
Here is a typical ANM plot:

Readers here may be surprised and annoyed that electricity is being thrown away whilst many households are suffering energy-poverty. 🙁 

You may also feel it unfair that those consumers on pay-monthly accounts can take advantage of Time of Use tariffs (Octopus Go) and Nodal Pricing, which is denied to households who have pre-payment meters.

These are matters concerning ethics, not just technology.
That's why the Parliamentary Committee on DESNZ wishes to hear from you!

@transparent yes your assumption is correct it is an Octopus tariff and the PowerUp scheme which started 14th August is an Octopus scheme trial with the local DNO in Cambridgeshire. You receive an email before each PowerUp event to opt in and then Octopus monitor the energy used in the period and then credit your account for the amount :-). Doing the first one today at 2pm for 2 hours 🙂

"Random Times" = Depends on the weather and how much renewable energy is produced on the day, today plenty of wind!

@technogeek Ooooh! Power Ups looks interesting; have signed up with OE to know more when it extends to SSE area. Regards, Toodles

Hi, I've been browsing the forum for a few weeks now and it's proved invaluable. My thanks to all.
Our social housing landlord has at last agreed to improve the heating on our small, all electric estate. It'll be A2W heat pumps with Solar PV for hot water (no batteries). I've done a bit of research to try to understand the basics but the one thing I'm still not clear about is whether the extra energy generated by the Solar PV array (and not needed for water heating) will automatically be used to power devices in the home before being fed back to the grid (via SEG). Could someone clarify this please? Thanks.