Scrutable

IvanV wrote: Mon Nov 17, 2025 4:22 pm Whilst this - the solar panel bit at least - sounds rather amazing, we should remember that only about 20% of the world's final energy consumption is supplied by electricity. But on the other hand, that doesn't imply we need 4 times more on top. Electricity can usually be used with about 2 to 3 times the efficiency of other energy sources, at least for common large fossil fuel powered applications like road vehicles and space heating. So replacing the rest - in terms of gross energy requirement - would only require about 1.5 to 2 times more.

That 20% figure is wrong though, that’s not final energy usage. The figure Michael Liebreich uses is over 30% here: https://about.bnef.com/insights/clean-e ... et-part-i/ so we’re over 50% better off than you think

Grumble wrote: Mon Nov 17, 2025 8:34 pm

IvanV wrote: Mon Nov 17, 2025 4:22 pm Whilst this - the solar panel bit at least - sounds rather amazing, we should remember that only about 20% of the world's final energy consumption is supplied by electricity. But on the other hand, that doesn't imply we need 4 times more on top. Electricity can usually be used with about 2 to 3 times the efficiency of other energy sources, at least for common large fossil fuel powered applications like road vehicles and space heating. So replacing the rest - in terms of gross energy requirement - would only require about 1.5 to 2 times more.

That 20% figure is wrong though, that’s not final energy usage. The figure Michael Liebreich uses is over 30% here: https://about.bnef.com/insights/clean-e ... et-part-i/ so we’re over 50% better off than you think

The article you quote makes exactly the same argument as I do. Ie, in matter of fact it is currently 80%, but when you replace it, it will be less. Though my adjustment is more optimistic than in the article.

Grumble wrote: Fri Nov 14, 2025 11:28 pm As she’s looking to remove the majority of subsidy payments for heat pumps, maybe she could soften the blow by reducing VAT on them, like Belgium is doing (down to 6% in Jan).

I think the only thing that’s happened for heat pumps is the addition of air to air to the boiler replacement scheme. Which is good. Not sure why this is mooted as being good for small homes particularly, big office blocks these days are normally heated with air to air heat pumps.

Gfamily wrote: Fri Nov 07, 2025 5:29 pm

Gfamily wrote: Fri Nov 07, 2025 12:53 pm

IvanV wrote: Fri Nov 07, 2025 10:40 am Feeling lazy, I just asked an AI how much fuel duty and VAT you would pay on fuel for an average car if you drove 7,000 miles in a year, and the answer is about £1400, or about 20p per mile.

My (non AI) calculations were different (for 7000miles/year average)
average consumption (petrol) -> 39mpg ==> 180gallons
Fuel cost (@£1.32/litre ==> ~£1100
Of which VAT @20% ==> £188.33
Duty Paid (£2.40/gallon) ==> £432
Total tax ~£620

I've done an extra step -
A link to a Google Sheets which has costs and levies for ICE (petrol) EVs (charge at home and charge elsewhere) and Petrol Hybrid

https://docs.google.com/spreadsheets/d/ ... sp=sharing

You can play around with the numbers to see what taxes/levies are collected with/without a per/mile levy, and how they compare with the amounts collected for ICEs

Updated for differential 'per mile' rates as will be implemented

Grumble wrote: Wed Nov 26, 2025 7:16 pmNot sure why this is mooted as being good for small homes particularly

In terms of retrofitting to a house that previously had standard central heating, I guess smaller homes are more feasible for converting than large ones because it’s easier to install the necessary ducts.

and there are monobloc air-to-air pumps that heat just a single room. Nothing but a duct cover on the outside all the mechanism is on the interior. Just needs two 6inch-ish holes through an external wall and a power supply. No extra ducting needed.

Might be just the thing for our 1960's 3 bed bungalow.

Lew Dolby wrote: Thu Nov 27, 2025 2:15 pm and there are monobloc air-to-air pumps that heat just a single room. Nothing but a duct cover on the outside all the mechanism is on the interior. Just needs two 6inch-ish holes through an external wall and a power supply. No extra ducting needed.

Might be just the thing for our 1960's 3 bed bungalow.

And I believe a lot of them can also be used for air-con cooling of rooms in the summer.

nekomatic wrote: Thu Nov 27, 2025 8:07 am

Grumble wrote: Wed Nov 26, 2025 7:16 pmNot sure why this is mooted as being good for small homes particularly

In terms of retrofitting to a house that previously had standard central heating, I guess smaller homes are more feasible for converting than large ones because it’s easier to install the necessary ducts.

Robert de Niro in Brazil

Ducts are easy to install via attics, and a bit harder to install under raised floors. Ground storeys with concrete floors and middle floors are harder, although ground floors are often more open and more suited to wall mounted ductless systems.

nekomatic wrote: Thu Nov 27, 2025 8:07 am

Grumble wrote: Wed Nov 26, 2025 7:16 pmNot sure why this is mooted as being good for small homes particularly

In terms of retrofitting to a house that previously had standard central heating, I guess smaller homes are more feasible for converting than large ones because it’s easier to install the necessary ducts.

Robert de Niro in Brazil

You don’t need to install ducts though, you would have mini-splits. Wall mounted units that you’re probably familiar with from workplaces.

Grumble wrote: Thu Nov 27, 2025 11:29 pm

nekomatic wrote: Thu Nov 27, 2025 8:07 am

Grumble wrote: Wed Nov 26, 2025 7:16 pmNot sure why this is mooted as being good for small homes particularly

In terms of retrofitting to a house that previously had standard central heating, I guess smaller homes are more feasible for converting than large ones because it’s easier to install the necessary ducts.

Robert de Niro in Brazil

You don’t need to install ducts though, you would have mini-splits. Wall mounted units that you’re probably familiar with from workplaces.

It's probably most efficient to use a ducted split system for bedrooms upstairs, and ductless mini-splits for large downstairs spaces.

dyqik wrote: Thu Nov 27, 2025 11:38 pm

Grumble wrote: Thu Nov 27, 2025 11:29 pm

nekomatic wrote: Thu Nov 27, 2025 8:07 am

In terms of retrofitting to a house that previously had standard central heating, I guess smaller homes are more feasible for converting than large ones because it’s easier to install the necessary ducts.

Robert de Niro in Brazil

You don’t need to install ducts though, you would have mini-splits. Wall mounted units that you’re probably familiar with from workplaces.

It's probably most efficient to use a ducted split system for bedrooms upstairs, and ductless mini-splits for large downstairs spaces.

Efficient for heating, not necessarily efficient for installation

Grumble wrote: Fri Nov 28, 2025 6:51 am

dyqik wrote: Thu Nov 27, 2025 11:38 pm

Grumble wrote: Thu Nov 27, 2025 11:29 pm
You don’t need to install ducts though, you would have mini-splits. Wall mounted units that you’re probably familiar with from workplaces.

It's probably most efficient to use a ducted split system for bedrooms upstairs, and ductless mini-splits for large downstairs spaces.

Efficient for heating, not necessarily efficient for installation

Installing ducts in attics with a central unit is efficient for installation, and usually more efficient for heating, unless you've got insulation between every room in your house.

Larger units are more efficient to run than smaller units, and this outweighs the efficiency reduction of heating less used rooms to a few degrees higher than they would be otherwise. Heat pumps are also more efficient if you keep the conditioned space at a constant temperature, rather than turning it down when you leave for a few hours.

Going to have to get into what would be best for my home at some point, my boiler is five years old so not making detailed plans yet, but will switch to heat pump when I can.

In other news, and very much on topic, this last 24 hours wind power on the GB grid has averaged 21.6 GW and 60.4% of demand. Never dipped below 20 GW.

Just had to replace the heat exchanger on our fifteen year old boiler at considerable expense, so the idea of a heat pump has moved up the agenda some way.

We had a survey for one a few years ago and didn’t go ahead but I think things have moved on a lot on the technology, planning and cost fronts since then so I’m expecting it to be an easier and more attractive option now.

nekomatic wrote: Thu Dec 11, 2025 1:33 pm Just had to replace the heat exchanger on our fifteen year old boiler at considerable expense, so the idea of a heat pump has moved up the agenda some way.

We had a survey for one a few years ago and didn’t go ahead but I think things have moved on a lot on the technology, planning and cost fronts since then so I’m expecting it to be an easier and more attractive option now.

Have a look at the Heat Geek Zero Disrupt stuff - a few videos on YouTube etc

Grumble wrote: Thu Dec 11, 2025 2:18 pm

nekomatic wrote: Thu Dec 11, 2025 1:33 pm Just had to replace the heat exchanger on our fifteen year old boiler at considerable expense, so the idea of a heat pump has moved up the agenda some way.

We had a survey for one a few years ago and didn’t go ahead but I think things have moved on a lot on the technology, planning and cost fronts since then so I’m expecting it to be an easier and more attractive option now.

Have a look at the Heat Geek Zero Disrupt stuff - a few videos on YouTube etc

We're going into our first winter since getting a Heat Geek installed heat pump. So far snug. We are outliers in that the house had never had central heating before so all new designed around the HP, but dealing with them as a company and the specific installer was only ever a positive experience. There are many other quality installer organisations and sole traders around, and plenty of resources now to help a homeowner vet them to weed out the cowboys (Renewable Heating Hub on YouTube is very good).

Zero disrupt is an interesting addition to the heat pump market. For their historic offering, Heat Geek were initially the first to guarantee a minimum SCOP,of 3.5 I think it was (Seasonal Coefficient of Performance, essentially an average efficiency of the heat pump for heat and hot water over the year, 3.5 means on average you got 3.6kWh of heat out for each 1kWh of electricity). I don't think they are the only ones to minimum guarantee any more but their guarantee is higher than the others, but they were usually the most expensive too. Zero Disrupt offers to make the barest of bare minimum changes to your existing heat distribution and hot water setup, so gets the lowest install prices currently around but at a lower guaranteed efficiency (3.0 I think). It is an interesting compromise of lower initial outlay versus higher ongoing running costs but still with high confidence of a quality install. Previously I think the choices to buyers were a few options of high initial cost medium or low running, or medium initial with significant risk of very poor performance from a botched install and expensive to run to boot, so Zero Disrupt is a good addition to the pallette.

The Boiler Upgrade Scheme grant that helps people install heat pumps in the UK only requires a laughable 2.0 SCOP, and since electric is currently 4x the cost of gas here it is just a nonsense in my view. Generally it is accepted that a SCOP 3.2 to 3.5 breaks even with gas due to boilers getting less efficient with age and the distribution systems usually being poorly balanced. A Zero Disrupt could cost you more to run than gas, but is more likely to be in that break even range. I think I'm on track to get around 4.0 or better, but my old system was electric resistive so 1.0 is my break even. I don't understand 2.0 as a minimum for the grant, if we want to electrify for the environment and energy security, efficient electric home heating helps us massively and unnecessary inefficiency kills us.

Much of the disparity between electric and gas prices, "the spark gap", in the UK are policy costs, so the government have tools to narrow the gap if they wish to. If they were to phase VAT from electric onto gas, or some of the energy efficiency levies, borderline break even installs today would become majorly quids in.

Changing how the electricity market is structured would help in reducing our high electricity prices, which is one of the major hindrances to replacing fossil fuel usage in the UK. Generators bid to sell their electricity into the grid (from memory) for each 15 minute slot over the day. The grid accepts the bids from cheapest to most expensive needed to satisfy demand. Then all the generators are paid the price of the highest bid. 97% of the time this is generation fired by expensive foreign gas, even it’s only generating 1W over that window. Contracts for difference (CFD) exist though, whereby a generator is effectively on a contract where they have a fixed bid price over a number of years. If the market price is below that price, the CFD generator gets a top up to the market price, if the market price is below, they pay any excess back. The differences are factored into the actual wholesale prices paid.

The purpose of that market mechanism is to encourage new entrants into the market if they can generate electricity cheaper than the going market rates. The idea being that over time these new entrants will eventually squeeze out the most expensive generators and the price will drop. This takes time however, a lot of time. Reforming the market so that expensive gas is either sectioned off while still having some of the incentives to encourage cheaper entrants would drop the wholesale price. One way might be to split the difference between a generator’s bid and the highest bid. Another might be two have a 2 tier market, splitting fossil generation off from non fossil generation, and use that mechanism separately in both, but prioritising the non fossil generators. @Ivan will be able to think up better schemes.

Addressing electricity prices ASAP should be a priority for the government, it’s a drag on economic activity, allows Badenoch and fossil funded Farage to b.llsh.t about how renewables are all to blame, eases the cost of living for us ordinary folk, along with increasing the electrification of everything so reducing carbon emissions. Yes I have written to my MP.

Fun fact, the largest supplier of fossil gas to the UK is Norway’s Equinor, which is 67% government owned. Their cost of supplying gas is way below market rates (f.ck you Putin). The Norwegian government puts the majority of the company’s massive profits into a sovereign wealth fund whose profits in turn pay for something like 20% of Norwegian government expenditure. Clever them, we pissed our North Sea proceeds away on tax breaks.

bjn wrote: Sat Dec 13, 2025 10:04 am Changing how the electricity market is structured would help in reducing our high electricity prices, which is one of the major hindrances to replacing fossil fuel usage in the UK. Generators bid to sell their electricity into the grid (from memory) for each 15 minute slot over the day. The grid accepts the bids from cheapest to most expensive needed to satisfy demand. Then all the generators are paid the price of the highest bid. 97% of the time this is generation fired by expensive foreign gas, even it’s only generating 1W over that window. Contracts for difference (CFD) exist though, whereby a generator is effectively on a contract where they have a fixed bid price over a number of years. If the market price is below that price, the CFD generator gets a top up to the market price, if the market price is below, they pay any excess back. The differences are factored into the actual wholesale prices paid.

The purpose of that market mechanism is to encourage new entrants into the market if they can generate electricity cheaper than the going market rates. The idea being that over time these new entrants will eventually squeeze out the most expensive generators and the price will drop. This takes time however, a lot of time. Reforming the market so that expensive gas is either sectioned off while still having some of the incentives to encourage cheaper entrants would drop the wholesale price. One way might be to split the difference between a generator’s bid and the highest bid. Another might be two have a 2 tier market, splitting fossil generation off from non fossil generation, and use that mechanism separately in both, but prioritising the non fossil generators. @Ivan will be able to think up better schemes.

Addressing electricity prices ASAP should be a priority for the government, it’s a drag on economic activity, allows Badenoch and fossil funded Farage to b.llsh.t about how renewables are all to blame, eases the cost of living for us ordinary folk, along with increasing the electrification of everything so reducing carbon emissions. Yes I have written to my MP.

Fun fact, the largest supplier of fossil gas to the UK is Norway’s Equinor, which is 67% government owned. Their cost of supplying gas is way below market rates (f.ck you Putin). The Norwegian government puts the majority of the company’s massive profits into a sovereign wealth fund whose profits in turn pay for something like 20% of Norwegian government expenditure. Clever them, we pissed our North Sea proceeds away on tax breaks.

A provocative idea from Bryony Worthington - a major force behind the Climate Change Act - about restructuring the gas market between UK and Norway to take it away from being bought at market rates. She’s the sort of person who has the ear of governments, so it will be interesting to see if this goes anywhere. It would have a stabilising effect on our electricity prices because they are so dependent on gas prices.
https://www.energyflux.news/uk-norway-g ... -new-deal/

Article in Science about the rise of renewables.

https://www.science.org/content/article ... rough-2025

Grumble wrote: Sat Dec 13, 2025 10:28 pm A provocative idea from Bryony Worthington - a major force behind the Climate Change Act - about restructuring the gas market between UK and Norway to take it away from being bought at market rates. She’s the sort of person who has the ear of governments, so it will be interesting to see if this goes anywhere. It would have a stabilising effect on our electricity prices because they are so dependent on gas prices.
https://www.energyflux.news/uk-norway-g ... -new-deal/

I suspect this won't happen. Because the privatisation of British Gas has left a strong memory in Britain of the huge risk in long term fixed price gas supply contracts.

For just the same seemingly sensible reasons we see in the article, pre-privatisation British Gas made long-term fixed price deals with suppliers. But these suddenly looked very sick come 1990, when the price of gas crashed and stayed low for the best part of a couple of decades. Eventually customers benefited from those lower prices, but only because the government acted in bad faith to skewer the people it sold British Gas to. Of course British Gas was sold in 1986, before these contracts looked sick. But the regulatory rules for BG were much friendlier to BG than the privatised electricity companies, where proper competition was designed in from the start, though it became stronger later. Thus the rules made it look like British Gas would be recover the costs of its long term contracts, even if what eventually happened in the 1990s - a huge surprise from the situation of 1986 - were to happen. But come the 1990s, then the government gradually pulled the rug from under the new owners' feet, by injecting competition ever more strongly as time went on. It also broke up BG. It was careful not quite to bankrupt BG (by then, Centrica trading as BG, strictly speaking), but it was pretty close to the edge for a while.