ProDave

We found you need very little "plant room" space, and it all ended up distributed around the house. A Monoblock Air source Heat Pump, most of the works are outside. You might need some pumps, valves and expansion vessels etc inside somewhere. Hot water tank wants to be positioned central to points of hot water use to minimise delivery time. Ours is in an airing cupboard partitioned off a bedroom. MVHR is best in a warm part of the house, but can be put in a loft id the ducting is properly insulated.

As long as you get a 5 port or 5 terminal meter, it will do that. The 5th terminal is the output that is only energised when it is at the cheap rate. But Smart meters have come along and messed things up. You can aparently get a 5 port smart meter, but not all suppliers seem capable of actually making them do what it says on the tin, and lots of horror stories of the 5th output not turning on and off or the metering times matching the switching times. So if you do switch, ask for Economy 7 or preferably Economy 10 if available and don't mention smart meter and if that comes up in discussion say you don't want one. You will ideally need 2 immersion heaters one to come on whenever the cheap rate is available at the bottom of the tank, and another you can turn on at any time for a boost. If your tank will only take 1, then Horstman do a clever gadget that will let one work from the off peak supply with a manual timed boost.

You don't have to be precise if the size of the PV roof ends up larger just cantilever the end, a bit like I did with my balcony I did the same, poured 2 concrete pads for the balcony legs at foundation time, and only recently uncovered them and completed the job.

What is your monthly energy use now, now that the heating is off? In the absence of any other metering, that will give an indication how much of your usage is heating and how much is other stuff. Even in winter the other stuff uses more than the ASHP. Only when you know WHAT is using all the energy can you look into making it use less.

I guess if there was nothing registering on the normal meter? I once connected an electric boiler to the total heat board for a customer, it certainly seemed to fit the description of a heating appliance. In that situation getting 24/7 cheap rate almost made an electric boiler make sense.

White, has a very horrible habit of turning yellow over time.

Good riddance to the THTC tariff. It was a good idea in it's time, the chief advantage being the "total control" circuits being metered 24/7 at the cheap rate. But it became a very expensive tariff and with only SSE offering it there was no competition and you could not switch supplier. To convert, all you need is a simple Economy 7 or economy 10 supply with a 5 port meter, the 5th port being the SWITCHED off peak output. Economy 10 if you can get it is the best match to the old off peak times of THTC. The only thing you will need an electrician to do is then connect the total control circuits to the normal permanent supply. You will miss out on the 24/7 cheap rate which could have powered panel heaters or showers. Did you actually take advantage of that, or were you just using ordinary storage heaters?

And don't throw away the spare bit. Put another plug and socket on it and you have another extension lead.

It can be read via the IR port, that red flashing light is one of 2 IR sensors / receivers and the right gadget can read all the data. The rED thing was initially there to detect people trying to reverse the meter in the hope it would run backwards.

Is the Juliette balcony permanent, or just to get sign off? Will there be a real balcony later?

Yes exactly the same as my generation meter. Note the writing on it to avoid misunderstanding with any meter reader. Note also my import meter is displaying rED that means Reverse energy Detected (the small amount of export) It alternates between that and the import reading. Nobody has raised this as an issue yet.

How are you going to fetch the diesel? I bought a plastic 20L Jerry can for collecting fuel when I had a digger, those were the days I could buy red from a local supplier.

Not everyone has a railway in their garden. So tell more (in a new thread)

I first question WHY in needs to be perfectly level? That is not such a stupid question as it sounds. The holes obviously want to end up on the outside exactly right to line up with the holes in the Juliet balcony. But to ask for the holes to be perfectly level implies the fixings on the inside will be visible, so they too also need to be in just the right place. If so not only do the holes need to be perfectly level, but also perfectly perpendicular to the wall. If the internal fixings are not visible when finished then only nearly level and perpendicular are required. Also what are you drilling through? I assume ICF walls, so the start of the drill will be soft material, it is when you hit the concrete core that the drill is likely to be thrown off course?

@Thorfun You did better than me. What a lousy bloated, confusing horrible website, I never actually managed to find a price anywhere. At a low capacity of 1.5kWh then even if you could store that much from your PV and use it every day you would save about 50p per say, so if it really costs £1700 then it would take 3400 days tp pay for itself, that's a shade over 10 years. Then there is not enough details to even know if it would simply store any surplus that would be exported. No sign of current clamps or anything similar to measure your import / export just talk of connecting it to a phone app and putting you in control. I would keep on looking for something better with some idea it will actually do what you want, how it will work etc.

If it is any consolation, I was disappointed my air test came in at 1.4, though the tester was having kittens saying it was the best one he had yet tested. The building still performs very well, heating usage is exactly in line with what the heat loss calculation says it should be. There are no noticeable draughts and it fits my basic test that on a windy day you can open 1 window or 1 door with no perceivable draught entering or leaving that one open door or window. (previous house with all the plethora of individual extract fans, window trickle vents, cat flat, letter box etc, if you did that there would be a draught blow through and likely an internal door blow open or shut) So although it would have been a "fail" that does not mean it is a bad building and was a waste of time trying or it is going to waste a lot of energy. The flaw in your argument is if you knock down and rebuild you would just employ a specialist to do it all properly. I only know of one timber frame company that will erect a complete frame and guarantee a particular air tightness figure. And that is for the bare shell. You then have to guarantee that all your following trades, plumbers, electricians, even joiners, do not drill holes in your air tightness layer and destroy your good air test. It is a sad reflection on the UK building trade that most tradesmen in the industry don't have a clue about air tightness and think you are being silly when you talk about things like that. You really are best seeing to the detail yourself, you have done a large part of the house already, just carry on. With a rebuild I bet you would either still be doing the detail yourself, or complaining that it has been done wrong and having that same argument.

Picture zoomed further out to give context and one from inside showing lintels above the door and window? Are the lintels where the wall steps out? The house wall steps out, how is that supported or is that external wall insulation fitted that makes it step out? What are you hoping to achieve? It looks fine to me as it is as a useful outside / work / storage space. What to you need or want to get into it that requires a larger door opening?

In the 4 1/2 years, the total export (i.e. wasted) is standing at 334kWh (I have fitted my own export meter) Export happens when generation exceeds what the immersion heater can consume and nothing else in the house is using power. For a lot of the year I also dump to a small convection heater that is turned on when that situation arrises, but in the summer that is disconnected (though I could out of spite just move it to the garage) More export happens on the occasions when the immersion heater thermostat has cut out when the tank reaches maximum capacity. If I was able to get paid for the export at the silly low 5p per kWh that would only have earned £16.70 If I had a smart meter and signed up to one of the more lucrative export payment deals, that might have earned perhaps £50 in export. But any export payment would require it to have been an MCS install. Clearly the extra of an MCS install vs DIY would NEVER repay itself in export payments. If I add more PV that will be with battery storage, that is another topic for the future, I have to build the car port first where it will likely be mounted.

Can planners insert ownership clauses? e.g the annex may not be sold as a separate unit to the main house? I ask because near us there was a small cottage on a very large plot. the owner got permission for a new, very much larger house in the grounds in addition to the cottage. There is a clause that the plot title cannot be split. The present owner lives in the big house and lets the small cottage as a holiday let.

An update and a milestone. Each week I log all my meter readings, import usage, PV generation, ASHP consumption etc. Today, entering the figures into my spreadsheet revealed that I have self used £1499.79 worth of electricity since installing the PV. That has taken 4 years and 16 weeks to achieve that. It's all free now baring equipment breakdowns, That is shorter than the initial estimate of 6 years, due to the higher cost of electricity now. If electricity had been as high as it is now right from the start, payback would have been just 2 1/2 years. Starting to think of an addition to the system now.........

It will be the inverter capacity that limits how much of your stored energy can be used. Will your proposed PV and battery system be able to supply 14kW? If not it will never all be provided by "free" electricity.

An annex, is expected to share some functions with the main house, so perhaps limited kitchen or bathroom functions to the occupants use those in the main house. The one near you turned down probably had all that is needed to live completely independant to the main house and the planners thought it was a separate dwelling in all but name. What are you expecting from your annexe?

To be any use, an instant heater has to be at least 10KW and that will only give you a mediocre shower flow compared to an UVC. The chance of getting much "free" electricity from that with your solar PV is slim. You would be doing all your showering and washing at about mid day to get maximum sun. An UVC with a diverter just sits there with whatever spare PV energy going into the tank, and then just sitting there waiting to be used, day or night. It sounds like an accumulator is what you want for the water supply issue, but be prepared for another cupboard space to be used up by another big tank.

An "electric boiler" can be 2 types, one is a hot water storage tank with a low power heater, and the other is a high power heater with no storage it just heats the water as it passes through. Either will take up some space. So why not make space for a proper unvented hot water cylinder. This can be heated by the ASHP at a COP of at least 2, usually better, halving the energy needed to heat your hot water. And a solar PV diverter can connect to the tanks immersion heater giving you free hot water when the sun is out using up all the surplus PV not being used by something else. Is the water pressure really poor or is the flow rate poor? That is a separate problem to address and an accumulator may be the answer to that one.

If you want to keep the trenches open for a while I would get some cheap but thick shuttering ply, cut it in strips to match the trench depth, line both sides of the trench with it and then lots of timbers side to side cut to be a tight fit, to brace it and keep the sides under pressure. But surely all you want is a bit of paper from BC to say you have "started the development" So ask them for that. If you get that then does it matter if the trenches get filled in?