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In that case worth looking at something like octopus cosy as there are multiple cheap rates during each 24h period. As you say though, it’s worth weighing up whether it’s best to not worry about the very coldest of days.

That will be a whopping battery to run an ASHP for 24 hours in freezing weather. Not sure it's cost effective to have a battery that size rather than use peak time grid eleccy for the few freezing days a year most people have???

Something else I didn't know. Seems to be a saw tooth but with a wavy profile to avoid sticking, and produces less dust. Between a saw and a knife. £22 The Bahco insulation saw has been specially developed for cutting various types of insulation material

Neither. For simple white switches, I don't think you will beat Click Mode for quality, value and reliability. But Screweys don't sell them. Toolstation do. https://www.toolstation.com/click-mode-10a-switch/p73508 A little "quirk" of these switches is the switch mechanism can be removed from the plate, enabling you to mix normal and intermediate switches on the one plate. Almost like a grid switch.

The carb was left on the manufacturer's settings. The old carb is long gone.

Unburnt fuel possibly, you changed the carb, are these preset at manufacture? Is the old carb Knicknacked, if not I’d be tempted to pop it back on and see what happens

Currently most cost effective to have a battery big enough to see you through 24 hours in the winter when there is little generation. Charge it overnight to 100% at cheap rate then export any excess solar at higher unit price than you buy in for overnight. If you think you’re saving the planet by using maximum amount of generation on site, then that changes things.

May have a winter summer switch, to change the carb settings. In winter it could be running really lean.

3 phase (still no idea why anyone needs it in a domestic house) allows 16A per phase export on G98. So about 3.6kW X3. G98 you tell DNO after you start generating. But how you manage the phases, to make best use of the solar is something I have looked into. As most the house will only make use of a single phase.

Excess can also be easily and cheaply stored as domestic hot water

is the oil/fuel ratio correct? What colour is the sparkplug?

I haven’t but I’ll certainly look at it, thank you

It will be an MCS install i am having three-phase electricity supply if that makes any difference. I am very new to all this so please allow for my lack of knowledge. Don’t have any power cuts whatsoever.

Sounds about right, plus you delete a standing charge, so win win.

PV, battery and inverter can be confusing. So looking at battery first and how it powers the house. You need an inverter big enough so it passes enough kW to house so you don't draw too much from the grid. So for example if you have a 3kW inverter, every time you put the kettle on you could be drawing peak electricity in to cover base load, Same when cooking your tea. We have a 6kW and that suits our life style well enough. Then there's the question of DC or AC coupled battery. DC coupled generally will only supply a dedicated circuit in a power cut, AC can/will provide whole house. Then there's the panels and there relationship with the inverter, you can over clock (way more kWp than the kW rating of inverter), 90% of the year you loose nothing, a good summer day when you are producing bucket loads of energy the inverter will clip this back. So loads to think about. First MCS install or self install? G98 export limit (3.76kW) or unlimited or something in-between? Do you have power cuts?

From a quick peak at Google gives the following- 14300 kwh of gas@0.18kg co2/kwh gives 2574kg carbon per year currently 14300 kwh from HP at COP 4 uses 3575 kwh grid eleccy@0.177kg co2/kwh which gives 632kg carbon per year with HP. Google suggests 200-400kg of embodied carbon in boiler manufacturer and install. Assuming HP embodied carbon is the same as a boiler then first year of scrapping boiler and installing HP gives 632+300(boiler)+300(HP)=1232kg co2 for new HP versus 2574kg co2 continuing with gas boiler. Half the emissions in year 1 by switching to HP now. Second and subsequent years is 632kg co2 for HP versus 2574kg co2 continuing with gas boiler. Quarter the emissions in future years after switching to HP. More than happy to have these calcs challenged but seems that moving to a HP beats sticking with a gas boiler from an emissions perspective. OP has significant PV and storage which would likely lower the HP emissions further??

Have you run the system though PVGIS, I think they have a storage calculator now as well, but not sure on that.

Keep till the boiler packs up. Likely 10+ years.

Good evening all, I wondered if anybody could help. just trying to do some calculations in regard to our self build and solar panels. So within my plan I have added 16 integrated 410wp Marley solar tiles to be fitted on the roof. Although this has been calculated, one thing that hasn’t is what size inverter and battery for storage. I just wondered if there is anyone out there that has some good knowledge in this field? To give some perspective on the build it is a fair sized 4 bedroom detached house (approx 300square meters) that will have 2 electric vehicle charging ports and an ASHP. There will be two adults and a teenager living in the house. Any help or advice is greatly appreciated.

I must be bored. Here is a chart showing price comparison between insulation types. I have only got the prices from 1 site, and have used median k-Values. To get better results, do your own research. There is little difference between XPS and Phenolic at the 0.1 W.m-2.K-1 level, about £10.m-2. There is a 0.1m thickness difference though, which may or may not be important depending on how you excavate and dispose of the dirt. (as usual, there may be errors as I am tired)

If the embedded carbon/energy is a concern (and generally I don't suspect that it is for machines of this level of complexity), couldn't you gift it to a local gas spares place or GasSafe person for parts? When my combi was stripped out I did just that with the rather expensive heat exchanger that I'd put in just a year before, and the man was very happy. The sooner people switch to ASHPs and stop directly adding several tonnes per year of CO2 to the atmosphere via the flue, the better.

The 2025 flow chart has been copied and updated for 2026. But first job is a self assessment tax return. Haven't worked since Dec 2023! That'll teach me to rent out a house.

I’d stick with the boiler until end of life (or close to it) just from an environmental perspective (not replacing something that is still functional and effectively a very bloody good and efficient boiler

A word of warning. Bought a bunch of single gang LAP light switches (I think all 2-way) from Screwfix. In the last 2 weeks 3 of them have broken. I dismantled the internals of one and a small piece of plastic fell out - i presume the same has happened in the other two. I shall be replacing them all as they fail with another brand. Probably these: https://www.screwfix.com/p/knightsbridge-curved-edge-10ax-1-gang-1-way-light-switch-white/720yc?ref=SFAppShare OR https://www.screwfix.com/p/mk-logic-plus-10ax-1-gang-1-way-light-switch-white/13930?ref=SFAppShare Anyone recommend one over the other?

I used my husqvarna stone saw yesterday and noticed that it was occasionally popping and I could see flames coming out the muffler. I replaced the rings and fitted a new genuine carburettor at the same time. Does anyone know what might be the issue or how to diagnose it?