Running the heating from battery power

[Oldgreybeard]

How much heat does a dog put out?

I would imagine it varies a great deal, depending on size. Humans put out about 80W at rest, so you could probably scale it using mass and and get a reasonable approximation. As a complete guess a figure of around 1W per kg mass might be in the right ball park.

[nowty]

OGB's and my house are about the same size and both located in the South of the UK. But they are very different in construction. As you heard from OGB, his is to PassivHaus standards and probably exceeds it. Mine is a 70's standard detached house, large windows, suspended timber floor, no cavity wall insulation.

Stuff I've done to the house,

Stripped out the sagged 50mm of loft insulation and installed itch free (from recycled plastic bottles) 300mm loft insulation.

Fitted 50mm of underfloor polystyrene insulation and 100mm under the kitchen floor where I fitted a 1kW electric heated floor.

Replaced most windows with argon filled either double or triple glazed low E glass.
https://camelot-forum.co.uk/phpBB3/view ... f=21&t=617

Fitted new gas condensing boiler and replaced all radiators with oversized ones for the water temp to run at a more efficient lower temp as it increases the condensing heat recovery.

Fitted a DIY bespoke GSHP in parallel with the gas boiler. Gas boiler has been switched off now since April 2021 but still retaining in case of emergency.
https://camelot-forum.co.uk/phpBB3/view ... f=17&t=487

Fitted 12kW of PV, over 40 panels, wherever they will go.
https://camelot-forum.co.uk/phpBB3/view ... 579#p23570

Fitted 2 solar diverters to 300 litre hot water tank and storage heaters.

Fitted lots of batteries, mostly cheaper second hand ones.
https://camelot-forum.co.uk/phpBB3/view ... =14&t=1013

Fitted 3 storage heaters running on cheap rate leccy or from solar diverters. The diverters used to be quite important but since having the EVs, the EVs eat any spare leccy in the colder months.

Fitted two A2A HP's recently.
https://camelot-forum.co.uk/phpBB3/view ... =17&t=1043

Bought into both Ripple WT1 and WT2 projects to offset my leccy bill, almost all of which is in winter.

How much has all this cost ?

On one hand quite a lot, but on the other its mostly been self funded from the original FULL FAT Feed in Tariff revenue I earn on the solar panels, although some if its still on the never never, 0% credit card for another couple of years.

[Oldgreybeard]

Cost and payback time is an interesting subject in itself. I attempted to work out how long the additional insulation and airtightness cost of our new build took to pay for itself, and had to recheck the numbers a couple of times to be sure, as they just didn't look right. I knew how much it would cost to have built a conventional house, that just met building regs requirements for insulation and airtightness, and had a fair idea of what the running cost would be, based on the estimated heat loss from the full EPC that is used on new builds. What was surprising is that the biggest single additional cost was the heat recovery ventilation system. The additional cost for the insulation, airtightness and triple glazing was way down in the noise.

It took about three years to recover the cost of the heat recovery ventilation system, based on the energy it saves each year. The additional cost of the insulation, triple glazing and airtightness was paid back within less than a year, and could easily have been covered by choosing to fit a £15k kitchen instead of a £16k one.

The ASHP heating (and cooling) actually cost less than fitting an oil or LPG heating system (no mains gas here), so was really a no-brainer for a new build.

The thing with the longest payback time was the PV system. That took about 5 years to recover the investment in adding it, but it was cheaper to install during the build than it would have been to add it later, as we saved the cost of the slates and we already had the scaffolding up for the roofers.

When I completed the build I did really wonder why on earth all new houses weren't built this way. We've been "in profit" for the past two or three years, not just from the ~£1,000 FiT payments, but also because of the big reduction in running cost. You have to wonder quite why so few new homes are built to the same sort of standard.

One encouraging point was that the company we used as main contractor were building small developments for housing associations. Apparently some housing associations have realised that passive house standard homes are a tremendous benefit, not only to their tenants, but also to their own bottom line. Tenants that don't have to pay high energy bills and who live in homes free from damp and mould problems created by attempts to cut their bills, have more disposable income to pay their rent and their homes need less maintenance.

[Mart]

Hopefully adokforme will comment, as he got rid of his wet heating system, and uses two A2A units for heating. Now he has enough battery capacity (and PV) to heat the house using cheap rate .... I think.

Very impressive conversion.

[nowty]

This is my Energy Performance Certificate when I bought the house back in 2008.


And this is one which I needed to get the higher rate on my second FIT system in 2014. This was before any of the heatpumps, new windows or even more solar were installed. I wonder what it will be assessed as now.

[Stinsy]

23rd October - 22nd November 2021 (no A2A) I used 501.6kWh of gas.
23rd October - 21st November 2022 ("7kW" A2A on upstairs landing) I used 141.0kWh of gas.

I'm going to keep an eye on consumption this winter. I'm sorely tempted to swap my Gas boiler for a 6Kw ASHP, which I can run for 20 hrs a day from start of cheap period. And use the A2A as an augment in the coldest conditions and to help heat the house in the mornings on the cheap rate.

DHW I'm in 2 minds about. Do I plumb a cylinder into the ASHP? Or do I go resistive only?

[Oldgreybeard]

@Nowty, you just know what's coming below, don't you?

Full EPC, as built, from 2016:

EPC.jpg (86.03 KiB) Viewed 1498 times

The way the EPC system is structured means that, in theory, an EPC score of 100 is a zero energy home. Anything over 100 is technically a power station, in that the house exports more energy over a year than it uses.

[chris_n]

This is my Energy Performance Certificate when I bought the house back in 2008.


And this is one which I needed to get the higher rate on my second FIT system in 2014. This was before any of the heatpumps, new windows or even more solar were installed. I wonder what it will be assessed as now.

Probably take it down to a C because the primary heating is electric

[nowty]

Probably take it down to a C because the primary heating is electric

I was thinking they probably won't like the storage heaters.

Back to the 1970's.

[Oldgreybeard]

The EPC system does penalise electric heating. This is the detail for our house, and the ASHP gets penalty points relative to the rest, as does the excess PV powered hot water, because it's electric. Note the primary energy though, it's negative! :

EPC2.jpg (120.63 KiB) Viewed 1484 times

However, we do claw some back with the environmental impact, which shows we "absorb" CO2, as a consequence of the net energy export:

EPC3.jpg (81.34 KiB) Viewed 1484 times