Notes from an eco house. (2025 Update)

Not yet as I am upgrading some other stuff in view of the recent new standard for home storage batteries. My previous installer made a poor siting decision, which I did query at the time but was persuaded to accept, Hobson's choice at the time. I now have an export MPAN and am waiting for them to process the SEG details, After which I shall put some 2kW of PV on my shed roof.

I just case across Tomato Lifestyle:

and it selects one of about a dozen tariffs that have low rates at different times of day (and different standing charges)

As far as I can see they aren't checking the answers, so you can say you're a night shift worker with an EV and it'll select that profile, even if you aren't actually one of those.

It appears they don't actually control anything at your end, so if don't have the meter switch your heating that doesn't matter (in fact it's better, since they don't appear to tell the meter the right ALCS timings)

From a brief bit of messing around with their quote thing, the tariffs are:

Tomato Lifestyle Fixed TP October 2024-V1-Tariff-EDE Tomato Lifestyle Fixed TP October 2024-V1-EV Tomato Lifestyle Fixed TP October 2024-V1-Tariff-Solar Tomato Lifestyle Fixed TP October 2024-V1-Tariff-Battery Tomato Lifestyle Fixed TP October 2024-V1-Tariff-WFH Tomato Lifestyle Fixed TP Octobe 2024-V1-Tariff-9to5 (yes, with typo) Tomato Lifestyle Fixed TP October 2024-V1-Tariff-Nightshift Tomato Lifestyle Fixed TP October 2024-V1-Tariff-Pensioner

Depending on your usage profile, perhaps one of those is best for the storage heaters? (it seems that if you just say you have them, they give you the EDE tariff which is what you get without answering yes to any of the questions)

They seem to be quite small and some folks are a bit wary after being burnt by Bulb et al, but the tariffs are interesting.

Theo

In message <14s* snipped-for-privacy@news.chiark.greenend.org.uk>, at 17:50:09 on Mon,

Go steady with the "single skin brick", it's usually not a skin of single bricks, but double thickness. As a result when I've had such houses (and some older ones had even thicker walls) I've never felt that the leakage through the walls was significant.

It works the other way round in the summer - nice and cool inside the house.

....Even with a smart meter.

Doesn't work for me either, but other comparison sites do.

"The Gas Enquiry Services provides your gas usage data."

Oh, but it is significant.

Do the sums.

Ah yes - U switch works. But I had to tick a disclaimer confirming I was the bill payer, and provide an email address. Really, I think the system should be far more robust and protect confidentiality. It's not anyone else's business, after all.

Anyway(!), I sort of obviously couldn't vary the address but electricity consumption looks high at 11,500 kw/h per year. For just the hob she's kept gas going (300kWh). At best I'd say the benefits of the ASHP over gas are going to be slim - that's about 30,000 'gas' kw/h taking a 3x factor for the ASHP.

Interestingly (to me) much the same as a mate's 5 bed 80s detached home on the south coast: 10,000kwh electricity, 31,000kwh gas.

Quite an eye-opener for me - just hadn't realised the ranges of consumption. Enough to question the usefulness of averages . . .

The relationship between heat loss and floor area is interesting. A small London flat would fit into my living room...

The area of roof and floor scales with the ground floor area of course, irrespective of how many storeys there are.

But the shape of the property influences wall area greatly, with a circular house being best for heat loss and a long narrow one or L shaped being worse. And needing far more wall insulation.

But shapes being constant, heat loss will scale with ground floor area ...

However for normal-ish houses you are probably looking like you need around 25-50W /sq meter for an English winter, and up to 200W/sq meter if its single brick.

I am a but light on peak heating at around 33W/ sq meter. On boiler capacity. The UFH is rated at 50W/sq meter and works OK

I think when comparing houses we ought to say what the average annual energy per sq meter is.

Interestingly multi storey houses benefit from no external floor or roof area and can be very efficient

Ah, this must be it:

Yes I do wonder and considering Octopus' meteoric rise could it come unstuck?

In the meanwhile Tomato's offerings are tempting except for my gas and electricity bills combined are £450 2024-25 and £280 of that is standing charges. I am minded to stick with Octopus for the higher SEG and invest £500 and a bit of labour time to totally offset the standing charges.

I ought to insulate more and move to electric heating as I become more decrepit but the return will likely never pay back, this house is semi detached to what was an identical 2 up 2 down that has been extended twice and that will be the fate of this within a few years after we are gone.

BTW this November-Jan25 has been considerably worse for solar than the last two years.

I'm seeing 11 panels @ £50, inverter £700, £1,800 ex VAT total.

Energysavingtrust suggests less than that even in the South East.

So that

My 1976 semi does not have the usual sand-blinding immediately below the DPC but seems to have some sort of smooth aggregate material that looks not too dissimilar to those pink potatoes that the supermarkets sell

The original DPC is just flimsy black plastic like those rolls of black binliners, so if they walked on it, laid over those strange aggregates then it could easily have punctured.

After removing the screed the colour of the slab changed quite noticibly over the following few weeks as presumably any residual water vapour in the slab dried out. I suspect the marley tiles laid on bitumen was acting as a secondary DPC ever since the house was built.

Ice box, especially if there is a gable end that is exposed to significant wind chill too. Then those huge fire places and chimneys act like massive reverse radiators, sucking heat out of the 'thermal envelope' and emitting it out through the exposed chimney up above the roof line while the internal flue stacks conduct heat out of the heated space into the (uninsulated) section of the wall.

Barely an inch of PIR internal insulation would reduce the heat loss to that of a 1970's cavity that had been insulated with rockwool, ignoring the massive heatloss caused by fireplaces and chimneys. If these are still present then external wall insulation would be more effective, even more so if the above-roof chimney could be removed together with the section of flue inside the unheated loft.

How are you getting £700 for the inverter? A 4.6kW Growatt string inverter is £388, and the smaller ones are £150-300. None of their string inverters are over £400.

If you go for a hybrid inverter then they're £600+, but those are designed for also charging battery storage.

(depending on your setup, it may be better to have a mains-connected battery inverter, rather than a combined hybrid unit. Means you can put the panels on the house and the batteries in the mains-supplied shed, rather than having to run chunky DC cables between them. You can always used one of those to add batteries to an existing solar install at a later date)

Depending on your inclination and azimuth it'll be different, eg for Glasgow facing due east it's 654 kWh/year. Due north it's 420 kW/year. But they're still not a million miles from the ballpark figure.

Theo

Only if you have a super-insulated HWC else you will be adding more core heat to a property that may already be hot from solar gain on a hot, sunny June/July/August day.

My 3.9kWhp system generates between 3,500kWh and 4,000kWh per year. I'm in Surrey and the panels are facing SW.

I would suggest there is also third factor: security.

#Paul

Security of what?