A heavy heart

[majorbloodnock]

Feeling rather pleased with ourselves in the Bloodnok household. We’ve been researching for ages and, after finally deciding to take the plunge, have now been able to wave goodbye to our old oil-fired boiler and welcome in a brand spanky new air source heat pump, a whole roof’s worth of solar panels and associated inverter and battery. Net result is that our energy performance certificate for the house has changed from a band D to a band B; not bad, I reckon, for a 1930s house.

The novelty will obviously wear off soon, but for now we’re having fun with the apps telling us how much leccy we’re generating and how little the heating is using up.

Smug moment finished now.

[Daphne]

Well done Major!  So, all round to yours for lots of extra festive sparkly lights then?  People around here seemed to have reined things in a bit!

[Beantree]

We may perhaps need that kind of setup here? News says to expect power cuts because 15 of the 56 nuclear power stations have been shut down, but I don't know why? We do have wind turbines and solar panels all over the Country, but on a cold, still and cloudy day there is no way the system can cope with demand.

Do you have an idea of payback time for your system Major?

[majorbloodnock]

On 12/25/2021 at 10:21 AM, Beantree said:

Do you have an idea of payback time for your system Major?

That’s a very difficult question to answer because of the number of moving parts, but I can give an outline of the key facts for an idea of how it fits together.

The air source heat pump, new water cylinder and all associated general gubbins came to about £15k, which should result in RHI repayments of just over £9k over the next 7 years, hence a net installation cost of about £6k. The solar panels, inverter and battery were done through a scheme with the county council allowing for a bulk purchase agreement for the installers and therefore a lower cost to us. In total, we got 18 panels, a 6kWh battery and all associated stuff for £7.5k, which, compared with other previous quotes, effectively meant getting the battery for free.

We were in the position of having an oil-fired boiler that was in perfectly good order but about 20 years old and therefore a bit of a ticking time bomb. We wanted to replace it whilst we had time to do it rather than wait until the decision was forced on us. We were using about 2 tanks of oil a year, and the cheapest I can find oil at the moment means that’d be about £1.3k. Based on the ASHP running costs over December, if the current year was the same weather throughout we’d be looking at almost exactly the same cost if we bought all the leccy from the grid (Octopus Energy). Fairly obviously, the weather won’t be the same, and especially will be far warmer in the summer, at which point we’re unlikely to be needing the ASHP to heat the house at all, so only time will tell how much lower the energy demand will be.

That said, we’re also not buying all our leccy from the grid. On the most overcast days we’re still generating at least 1 kWh of solar energy, and when there’s capacity to do so, the battery is recharged during off peak times to be consumed when the leccy price is peak rate. In good sunlight, we can get up to about 6.5kWh, and the ASHP has been consuming a December average of 21kWh per day. Come summer we should be covering all our daily energy from solar and probably exporting a tangible amount back to the grid.

We didn’t in fact do all this primarily for financial reasons. We just wanted the figures to be good enough not to be prohibitive. However, our house’s carbon consumption is now about a sixth that of an average property and there are still improvements we can make; we could in theory get low enough to become a carbon sink, effectively generating a negative amount of CO2. Let’s see how things pan out.

 

[mullethunter]

I am very jealous Major. We live in a 1930s dormer bungalow which is appallingly inefficient. We have a fairly new (5 years old) gas boiler for hearing and hot water, but because of the dormers and old, leaky double glazing we absolutely haemorrhage heat.

If we had the ££ to do what you’ve done we most definitely would (although probably also need to re-roof to allow us to properly insulate the dormers and replace all the windows). 

Maybe one day! 

Good on you though - don’t blame you for feeling smug!!

[Beantree]

Certainly give me lots of food for thought @majorbloodnock. We are using 8-10 litres of oil a day during the 3 heating months and you are using 4€ of electricity, so we could save perhaps 800€ or more if it is cheaper than burning wood in the evenings for two months. Then there is the export of electricity which I have no idea about here, although lots of properties have panels on the roof because all houses face South. Our very large garage gets too hot in Summer (36C) because the grey slate coloured steel roof is uninsulated. To fit panels on it would need extra lintels I think, but then the roof could be insulated (wouldn't put them on the house roof because appearance for selling an old property is vital here). The big drawback is our limited electricity supply which trips out if exceeded. We could upgrade it (and the supply cables are already in) but are then penalised by a much higher standing charge. Do you know what your maximum instantaneous load is?

[majorbloodnock]

@mullethunter, are you sure you know where and by how much your property is losing heat? We invested about £40 on a small thermal camera, then on a sub zero night used it to see which parts of our pace were hotspots. The results were sometimes surprising with expected culprits being better than expected and heat being lost where we didn’t expect. That’s why we replaced our front door to great effect.

@Beantree, I don’t know about max instantaneous load, I’m afraid. However, I do know that GB Sol make solar panels that are almost indistinguishable from slate tiles. Not going to suggest they’re as cost effective as normal solar panels but it’s certainly something to ponder. Seems they’ve been approved in conservation areas where other PV installations were non starters.

[mullethunter]

Thanks Major I might actually do that

[The Dogmother]

This is all very interesting, and something that's bene on my mind recently; my gas boiler is about 20 years old now, and while spare parts can still be found, it isn't going as well as it used to. As you said Major, I would rather replace it while it's still running and I have choices, but couldn't run to air source heating. The log burner really helps to keep it warm in the winter, and I don't pay for the wood.

 

My house was built in 1897, of locally fired brick and has solid walls rather than cavity. I am well aware that it is pretty draughty, and had the roof properly insulated when it had to be replaced a few years back. Living in a conservation area places certain restrictions on what can and cannot be changed. I think I may see if any of the neighbours has a heat imaging camera that I can borrow.

[Beantree]

Maximum instantaneous load is easy to work out @majorbloodnock. It's the sum of the major electrical appliances that could be running simultaneously. Forgetting the solar panels, add the maximum input of the heat pump to the hot water cylinder and the cooker. Disregard any electric shower as we don't have them here, only mixers because of supply cable limitations and three phase supplies. That figure will tell me if a heat pump is even feasible here. Then I'll check what effect the change in standing charge is, as it may cancel out any savings.

[majorbloodnock]

@Beantree, the ASHP is a Mitsubishi Ecodan (PUZ-WM85VAA(-BS)) rated at 8.5kW, and with a nominal and max running current of 9.1 and 22 amps respectively. Our cooker is a Rangemaster 90 dual fuel with a maximum rated load of 7.4kWh. All those figures are straight from their user manuals.

Separate to that, our solar monitoring app shows since the system was installed the maximum spike in electrical load was around 7.5kW, and that was just once. That’s not load on the solar panels but draw from wherever it can get it.

Hope that helps.

[Beantree]

That's very helpful @majorbloodnock, thank you. My calculations say we would need to upgrade our supply to 12 KW, from 6 KW which is another 80€ per year , so not that much. They do sell hot water cylinders here that only have a 1KW element, which gives us some flexibility meaning perhaps we could drop to 9KW? So now it will be down to EDF to tell us if their single phase supply can deliver that. If we have to go to three phase to get more the whole idea collapses, because 12KW is only 4KW per phase, or 16 amps.

Thinking more deeply, the idea of payback isn't really relevant when we only have two options; wood pellets or ASHP. Oil boilers are now obsolete here, so when they break they can only be repaired, they can't be replaced. The idea of lugging sacks of pellets around and pouring them into the boiler doesn't appeal. I don't think any funding grants are available here, but we will have to ask. Brexit and the exchange crash cleaned out our savings, so we have no means of paying the whole amount up front. 

Your comments longer term will be interesting, particularly in a long cold spell.

[Daphne]

I have a friend, an engineer, here in Portugal, who is rigging up some kind of system to get his pellets automatically from the storeroom on the ground floor up to the pellet burner on the first floor.  Next time I see him I will ask.  The idea is to future proof the system as he is in his 60s now.  He wants it so that he can buy a pallet load of pellets, get them delivered and stacked into the store by the seller and then automatically somehow they get moved upstairs.  Pellets are becoming very popular here as 'wood' is not only a primary industry, it is the primary industry around here, trees as far as you can see and we have several pellet factories within a 20km radius.

I have to say our pellet burner heats our single large living/dining space far more quickly than the woodburner, but it doesn't retain a background heat overnight and into the next morning.  

[majorbloodnock]

@Beantree, just a small point to note is that the ASHP heats the water cylinder as well as the house. You might want an element as a backup but it shouldn’t be running simultaneously with the ASHP. We’re only on single phase and it seems fine. Our experience is that a good installer is key.

[Ursula123]

@Beantree apparently there are a lot of grants available for making homes more eco and economical to run, from January it is all being placed under one hat with dedicated advisors, my friend who is a hand holder has said that she will run us all through the options when published which I will happily share with you. Did you benefit from the €1 insulation the government offered?
We have a 11kw pellet burner in the lounge which heats the house 120m but as Daphne says once you turn it off the temperature starts to drop however we did purchase the wifi option which means we can turn the fire on so the house is warm when we get home.

[Ursula123]

@beantree look at this website https://www.economie.gouv.fr/particuliers/prime-renovation-energetique

[Beantree]

We didn't need the 1€ insulation @Ursula123, because we already have 9" of glass fibre up there. We've also heard some horror stories about cowboys putting it in. We need a system to tie into the central heating as there isn't a centre point as such in our house. We're in the planning stage on the basis that we should be prepared if our oil boiler fails. We have a central log burner with an air circulation system which blows hot air to either end of the 'longhouse', but it's not very good, which is probably why the Dutch (who started the renovations) installed central heating. Thanks for the link.

I'd need to check the details on the hot water @majorbloodnock. Your cylinder probably has a heating element to get the temperature up to 60C to kill Legionella, but I'd perhaps be thinking about solar panels for the water and keeping it completely separate?

[majorbloodnock]

@Beantree, there is certainly a legionella cycle within the ASHP’s repertoire. I suspect it makes use of a heating element for that, but it’s the heat pump that controls it, so load would still not be in parallel, I think.

We thought about and discounted solar thermal water heating in conjunction with the ASHP, particularly since roof space seems to give better returns with the solar pv. However, it’s still a possibility and we’re watching developments quite closely.

[majorbloodnock]

Oh, and it gets better.

After the installation of the ASHP, we had one remaining cost - drainage and removal of the oil tank - and so were expecting to have to fork out a couple of hundred pounds. Co-incidentally, our neighbours needed an oil delivery and the tanker driver decided their tank was no longer safe to deliver to. Net result is they took our tank and the remaining oil, saving themselves four figures, we got our tank removed at no cost to us and neighbourly goodwill abounds. Couldn’t have worked out better. Smug moment has been extended.

[Beantree]

Opened up the weather forecast site here, purely to establish the daylight hours here now (9 and one minute), as our hens have started laying. The pop-up advert said that grants are now available for ASHP, up to 10,500€. Started to fill in the questionnaire only to find the next page was all our contact details, so stopped at that. There would be a lot of work we'd want to do first anyway; put in the reinforced concrete base, footpath on stilts around it, repoint the wall behind and put the hole through it for the pipes and electricity cable (too many walls collapse at that stage here). The starting point will be checking the suitability of our electricity supply cables.

Our oil tank is a 1500 litre plastic unit in the garage. Was thinking of cutting it in half vertically to make a shallow double pond?