Heat Pumps

[albie]

That would depend on the pattern of usage, BST.
No-one is suggesting it would be free, but it may be lower cost than the current energy provision.

Don't forget that the solar could feed the house demand in summer,  for fridge freezer air conditioning and electric car for example.  The net annual position is what is under consideration.

Are you selling excess back to the grid for peanuts, when you could reserve that excess for evening use? If so, what is the additional cost of sized storage?

There is no general rule to apply...how important decarbonisation is varies from person to person.
As I said, get a professional assessment.

Octopus must think that there is a value in this approach;
https://www.hvnplus.co.uk/news/octopus-energy-to-offer-solar-pv-service-alongside-heat-pump-installations-18-01-2023/

[BillyStubbsTears]

Albie.

I get your point on using solar power in the summer, and the net position.

My point is that solar doesn't come close to providing the power you need to run a heat pump when you need to run a heat pump. There's no professional advice that can change that.

Let me give you my numbers.

Since the start of December, we've used 3000kWh of gas for heating and hot water. That's cost about £300.

If that had been supplied by a heat pump, we'd have needed about 1000kWh of electric to service it.

I haven't got solar power yet - I'm on a waiting list.  But I have got a professional app that predicts, from my house location and orientation and the actual weather, what solar electricity I would be producing with the system I intend to get. It says I'd have made 92kWh since the start of December. So I'd need 900kWh of grid electric. Which, at current rates is £300.

As I say, when you need the electricity to run the pump, solar doesn't do any more than scratch the surface.

And yes, of course solar is great in the summer. But you don't need heating then. My point is that "solar" and "heat pump" are effectively two entirely separate decisions, financially. 

Don't get me wrong. I'm seriously looking at both.

[albie]

BST,

Yes, installing a heat pump and installing solar are separate financial decisions, but they are linked for those looking to decarbonise.

You would not install solar specifically to run a heat pump, you choose solar to manage down your energy bills over the full range of energy uses.
Adding an ASHP will increase electricity consumption, but reduce gas consumption.

So the task is to reduce the amount of energy that needs to be bought in, at rising costs.
What is the lowest cost method of reducing energy demand, and smoothing the peaks by transferring from day to night, or interseasonally, over the lifetime of the kit?

If you can reduce the heating season by shrinking the demand in autumn and again in spring, and reduce grid supply to winter top up from a renewable provider, then a 3 season coverage might give a summer excess to be redeemed as a credit in winter.

Whether you retain that summer excess in battery storage, or with an EV as the battery, or use the grid as a back up, is an available choice.
My guess is that EV will become the energy store (so called "vehicle to grid", or VTG). "Smart charging" using different tariffs will become the norm.

Trying to second guess the way taxation and grant support will move in energy is very difficult in a market without direct public sector presence.
The £3k deal BG and Octopus offer in England is £499 in Scotland, because grant support is higher.
You are paying upfront at todays installation costs (supported) to hedge against possible rises in supply costs in the future.

The starting point is you need to know what size of heat pump the property requires.
Here is a guide:
https://www.theecoexperts.co.uk/solar-panels/solar-with-heat-pumps
The heat pump costs given here have now been overtaken by the new support offered by BG and Octopus.

Residential solar would depend on the available roof space, alongside cost.
Once people have solar, they change their behaviour, so washing machines and dishwashers are in use when you have the juice.
With bifacial solar on the move, perhaps ground mounted become more attractive to some buyers:
https://www.independent.co.uk/tech/solar-panels-renewable-energy-bifacial-b2264534.html

Solar is a declining cost sector (per unit supplied), whereas electricity costs will rise again in April.
Neither political party has yet understood that the electricity supply market needs to be fully decoupled from gas supply and prices.

[big fat yorkshire pudding]

It's difficult to make the decision though without any sense of understanding what future energy costs might be. I'd like solar and a heat pump but I can't justify the cost.

[BillyStubbsTears]

Albie

I get all of what you are saying, but it's a blunderbuss response to a very specific point I'm making.


On the very link you posted, the EcoExperts say " Free solar energy can power other eco-friendly items, like heat pumps."

My point is that claims like this either clumsily or deliberately deceiving people. Solar electricity simply cannot make a significant contribution to the running costs of a heat pump, for all the reasons I've set out.

It could if and only if there was a way of storing solar electricity in July and using it in January. You ain't going to do that with an EV.

[albie]

BST,

The point of the link was to give an indication of the size of a heat pump required for different property types.
I clearly said so in post 32.

You are right to say some parts in the link are poorly written....solar is not free energy, there is the upfront cost to consider.
Obviously, if I put up a link to show a particular point, it does not mean I endorse everything in the link, that would be ridiculous.

"It could if and only if there was a way of storing solar electricity in July and using it in January. You ain't going to do that with an EV"....Billy, no-one is suggesting this!

The idea is that you retain any excess generation for personal use.
For example, transferring excess to an EV would displace energy cost from buying fuel, which gives a surplus which could offset the winter bill for electricity.

It is an alternative strategy to using the grid as sole reserve, but that is available.
I have no view on what is best for any particular case.

With a coefficient of performance of 3 or 4 to 1, you multiply the heat return on every unit of electricity consumed. Providing 25% (or more) of the electrical energy from a renewable source should be an attainable goal, whether bought in from a external supplier or self produced.

Once again, the big picture is about whole system costs, not specific elements within the wider energy supply.

[Superspy]

Just to digress slightly as I think you're both actually arguing the same thing and agreeing with each other, just from different angles down to how you've both interpreted the marketting...

I've had my solar panels in with a decent-sized battery and on Economy 7 for a few months now so if anybody has any questions or would like any info on it's performance or capabilities please feel free to ask. I know there are a couple of things I would have liked to have known up front, such as charge/discharge capabilities of the batteries, power generation differences summer to winter, etc etc.

[big fat yorkshire pudding]

What's your payback period looking like? Everything I read suggests it is just too long.

[SydneyRover]

Just to digress slightly as I think you're both actually arguing the same thing and agreeing with each other, just from different angles down to how you've both interpreted the marketting...

I've had my solar panels in with a decent-sized battery and on Economy 7 for a few months now so if anybody has any questions or would like any info on it's performance or capabilities please feel free to ask. I know there are a couple of things I would have liked to have known up front, such as charge/discharge capabilities of the batteries, power generation differences summer to winter, etc etc.

Do you have the payback period for a battery (separate from the panel system) Ss, most of the experts here are saying that it is not worth it atm and to wait till the price drops.

[Superspy]

Cool, couple of different angles on payback.

BFYP's first.

At the minute I can only go on theory and the quote I got because I've not had the system in a full year to see what the actual generation numbers are in all seasons but...

The payback period on my full system was quoted as around 8/9 years - slightly longer than a lot of systems because my panels aren't south facing, it's a split east/west system, so I need more panels to generate the same as a south facing system.
Whether this is "too long" or not obviously depends on your own circumstances - I have no intentions of leaving this house for 20+ years, so it feels like a solid investment to me.

The key with quoted payback periods is to go into it with your eyes wide open and understand the assumptions they make in the quote, because they can be hugely significant. The biggies are:

 - What the system will generate (obviously after a year you'll have a better idea of whether this was accurate) but you have to take it at face value to start with
 - Utilisation - how much of the generation you'll use vs how much you'll export to the grid (at a, usually, much cheaper rate)
 - Price you'll be paid to export (tied to the previous point and can vary wildly between suppliers at the moment)
 - Energy Price Inflation
 - The fact you're not on Economy 7 (or any time of use tariff - relevant if fitting a battery)

Assuming the generation numbers are accurate then the utilisation and inflation figures are critical.

With solar pricing where it is at the moment, I would expect a quoted payback of 6-9 years is assuming 70-80% utilisation and 20-30% export.
It's incredibly difficult to hit these numbers without a battery because during daylight hours in summer a lot of what you generate will go straight back to the grid. Even in winter you'll be generating more than you can use without seriously managing it, and if you're out of the house all day you've got no chance regardless of time of year. But with a decent battery system and managing your usage (as BST alluded to earlier) you can spread the usage through the day and night and get much better utilisation, paying the system off much more quickly.

Most solar quotes I've seen have an assumed energy price inflation of 8% per year. Higher energy prices obviously result in a faster payback (because each unit you generate and use saves you more off your bills). Before last year this assumption was very disingenuous in my opinion (bordering on pure sales bullshit), because the average inflation over the previous decade was 5%, and 5% compounded over a decade is vastly different to 8% compounded over the same period - so what you would have seen is that each year your savings weren't climbing by as much as the quote suggested.
But we're in a different place now with energy pricing - since I've had mine fitted prices have already gone up 25%, and will go up another 20% in April, so I've had something like 5 or 6 years of assumed inflation kick in within the first 6 months, meaning my savings will be higher than they assumed.

That, added to the fact that I've moved onto Economy 7 so I can charge my battery over night and utilise it during the day, reducing my bills even further, and that I've made some behavioural changes to take advantage of the technology, means I expect it to pay off faster than they quoted.

Obviously I'll have a better idea later in the year once I've got generation numbers for the height of summer, and I'll report back if there's interest.

[Superspy]

Do you have the payback period for a battery (separate from the panel system) Ss, most of the experts here are saying that it is not worth it atm and to wait till the price drops.

Hi Syd

By "separate from the panel system" do you mean having a home battery and purely charging it on a time of use tariff like Economy 7 without having solar at all, or do you mean a calculation for how long it would take to pay back a battery adding it to a solar system, so you have separate payback numbers for the battery and the panels?

If it's the former, then yeah it likely isn't worth it - or would take a LONG time to pay back, as you have to offset anything you save on a night-rate to anything you still need to use on a day-rate which would be more expensive.

Using Octopus figures as of today, the standard Yorkshire tariff is 33p/kWh, economy 7 is 43.5/18 (day/night)...so every night unit is 15p cheaper, but every day unit is roughly 10p more expensive.
If (miracle assumptions incoming) you bought a battery perfectly sized for your daily usage and could fully charge it over night - therefore never needing to use any grid power during the day, if the battery cost approx £400 per KW (not sure on the average cost at the minute) - then £400 / 0.15p saving = having to cycle your battery over 2600 times (over 7 years) to pay for itself.

In practice it's going to be much worse than that, as you aren't going to be able to completely stop yourself from using grid power during the day - it just isn't practical - so a lot of those savings will be negated if the battery isn't perfectly sized for your usage, or any of your usage peaks higher than what the battery can output (which it will if you use a kettle) and your usage will vary throughout the year so there's no such thing as perfectly sized battery..

If I've made a fundamental error in my maths there I'm sure somebody will be along shortly to correct me.

On the other hand - if it's a case of already having a solar system and wondering whether it's worth adding a battery to it - this presents a more interesting (and tricky) proposition because of the stuff I said in my last post about utilisation. Having a battery allows you to utilise more of what you generate by spreading it through the day and night, rather than exporting it back, meaning that having a battery also enables the overall system to pay itself off quicker.

But how much you save from doing this massively depends on your export rates. In this case a high export rate means a LONGER payback for a battery specifically, as the savings aren't as high - but if you're willing to use it like a tool to be managed you can do things to help with this too - at one point in December I was getting paid £1.40 per unit to export by being on an agile tariff.

Having had my system in for a few months now I wouldn't be without the battery, in all honesty.

[Superspy]

Sorry for the long posts there chaps - could have just said the top line numbers but got a bit carried away with the context for anybody who isn't familiar with this stuff.

[SydneyRover]

Full marks for effort Ss, I've just put a new roof on the garage which I'm hoping may see enough sun for panels as the house is too shaded. A battery would come a bit later.

[albie]

Putting the solar debate to one side, and getting back to heat pumps, here is the assessment of one who installed in earlier to replace a gas boiler;
https://foresightdk.com/why-i-replaced-my-new-gas-boiler-with-a-heat-pump/

Note this was written in 2019, and as always the tech moves on, so the cost of installation has fallen since then.
Some models now claim to be more efficient as well, offering a higher coefficient of performance than 3, which is the assumption used here.

The author is a professor working with energy efficiency at Oxford.

BBC Inside Science discussed heat pumps last night;
https://www.bbc.co.uk/sounds/play/m001h4cq
First 15 minutes.

Ps
Good point from Sydney....you don't have to do all at once, you can add to the system as you go!

[BillyStubbsTears]

That's really useful SS.

Question from me if you don't mind. What's the peak wattage output that you get from your battery? Checking my Loop app data, we rarely use above 3kW (usually when the oven and several hob rings are on). I'm wondering if a battery would be able to service that requirement without drawing from the grid (assuming it was sufficiently charged up of course).

[BillyStubbsTears]

Also, when charging your battery from E7, can you program that? I'm thinking that I'd want to fully charge it every night in winter, but probably not in high summer, when the solar panels would do the job.

[selby]

   Why would you buy something that is at best 30% efficient, if it was an everyday item you used to do a job you would lob it over the hedge.

[ravenrover]

Did I hear correctly this morning that E7 prices will be going up unlike standard tariffs?

[Dutch Uncle]

Can I just say what a good thread this is, I have learnt so much - many thanks to all contributors   

This board at its best

[albie]

   Why would you buy something that is at best 30% efficient, if it was an everyday item you used to do a job you would lob it over the hedge.

Because wind and solar are by far the cheapest means of adding new electrical generation capacity.
Not by a small amount, by a country mile.....so if you want lower electricity prices and reduction in fuel poverty, much better than relying on Mr Putin and his gas.

Another new report on the importance of heat pumps here;
https://bregroup.com/press-releases/bre-calls-on-uk-government-to-improve-the-energy-efficiency-of-britains-homes/

All this is building up to the UK upgrading its net zero strategy in April.
Low hanging fruit, and all that!

[BillyStubbsTears]

   Why would you buy something that is at best 30% efficient, if it was an everyday item you used to do a job you would lob it over the hedge.

What on earth are you on about?

[Superspy]

Tell you what, I'll start a new thread for the solar questions so as to not keep derailing the discussion about heatpumps.

[albie]

Some companies are starting to offer tariffs aimed at heat pump users.
Good Energy and Octopus are first out of the traps with this;
https://www.octopusreferral.link/cosy-octopus-tariff/

With the discussion on heat pumps and solar, it might be worth considering an installer who offers both, so you get an integrated heat and power solution.

This is also helpful if you want compatible warranty and service plan arrangements.

[BillyStubbsTears]

That Octopus plan is worth considering Albie, although I think you'd probably need 12kWh of battery storage to make it work.

We are using about 100kWh of gas each day in this cold snap. With an efficiency ratio of 4 on a heat pump, that would require 25kWh of electricity.

We use most of the gas in the morning and evening, so I could just about imagine topping up 12kWh into batteries at the cheap rates between 04:00-07:00, discharging that into the heat pump in the morning then topping up the batteries from 13:00-16:00 and using that for the heat pump in the evening.

25kWh of electric at the cheap rate is £5/day. Compared to a current £10/day to burn 100kWh of gas. So that's a big saving.

Downside to that is that would take all the cheap electric we could get. All the other electric usage in the house would be at the normal or high rate, excluding the little bit you'd get from solar at this time of year.

Definitely worth considering though. Thanks for posting that.

[Superspy]

It's probably even better than that, because my understanding of heat pumps is that you normally run them for longer as they run lower flow temps than a gas boiler.
So on top of what you're saying there BST, you'd likely run the heatpump at the offpeak times whilst simultaneously charging your batteries, as well as a little bit later in the day - meaning you'd need to use less of your battery storage specifically for the heating and some of it would be left over for the other household load.

You'd need to be super careful between 4-7pm though as those peak rates are a stinger, even compared to E7. But as long as you've got enough charge in the battery to cover that, which you should have if you've charged 1-4pm then it shouldn't be an issue, in theory.

If you look at this from the perspective of somebody who doesn't have solar or battery storage it's probably still a good deal IF you can avoid the peak usage 4-7pm, because the "day rate" is only marginally more expensive than a standard tariff, so if you run your heatpump in the off peak periods in the morning and afternoon, and shift any other usage you have control over to those times (dishwasher, washing machine) whilst avoiding the peak rate 4-7 then it should still offer a saving.

[albie]

UK Gov site has a tool which explains the suitability of different options for particular circumstances;
https://www.gov.uk/check-heat-pump

Details of your Energy Performance Certificate (EPC) are available to view.....mine was out of date, because of recent changes.

[albie]

Heat Pump Monitor is an interesting site for those thinking about an air source heat pump.
https://heatpumpmonitor.org/
The efficiency of different models is given (as Coefficient of Performance figures), but this will depend on other energy efficiency measures in the property.

To see the running costs at current prices:
https://heatpumpmonitor.org/costs.html

The price of electricity will change, and adding solar also changes the economics.
A full year of data is needed to get the whole picture.

[BillyStubbsTears]

I've just today had a 4kW solar panel system installed with a 9.6kWh battery. Now expecting to spend hours each day optimising the charge times to fit in with Octopus Agile rates.

[Superspy]

Nice one bst, was filling in my monthly generation numbers in yesterday and wondered about whether you'd bit the bullet yet.

I've started scaling back my eco7 charging as we're getting to the point where the sun can handle a chunk of the load. I expect to be doing almost no charging by the end of this month.

[BillyStubbsTears]

That's going to be the interesting thing SS - seeing how much to top the batteries up and how much to rely on the solar. I was pleasantly surprised that, when the solar panels were finally connected at 16:20 under slate grey skies, they were still pumping out 200W.  I know that's only a tiny fraction of capacity, but I was surprised they gave out anything, it was so grim.