The cost of a bath or shower - update

I last looked at the cost of a bath versus a shower back in 2015 [1]. Given the general increase in prices since then I was not too surprised at the increase in cost.

The total cost includes the cost of the water and the energy to heat it. It is still the case that the water cost is a bit more than the energy cost, despite the increase in the cost of energy, as long as the heat source is gas rather than electricity. Previously I had described two showers - a typical shower (7 minutes at 8l/min) and a shorter low-flow shower (4 minutes at 6 l/min). For both of these the water was heated with gas. This time I have compared the cost of a short low-flow electric shower with a typical shower heated by gas. Electric showers usually do have a lower flow rate, simply because you would need too much power to heat the water at the flow rate you get from a hot water cylinder (which is pre-heated).

Summary of assumptions.

• 88 litres for a bath vs. 24 litres for a short, low-flow shower (4 minutes at 6 l/min) or 56 litres for a typical shower (7 minutes at 8 l/min).
• bath water at 41°C and shower water at 39°C coming in from the mains at 14°C.
• Gas for heating at 85% efficiency.
• Electricity at 100% efficiency.
• Water price: 
• 0.139p/litre for clean water [2a].
• 0.256 p/litre for sewerage (from Anglian Water) [2b] charged for 90% of the clean water supplied.
• Energy prices based on the current price caps: 26.1p/kWh for electricity and 7.33p/kWh for gas [3].

Overall findings: 

• Costs (using gas for heating) are up nearly 60% from 2015. The increase for the water and for the energy are surprisingly similar.
• This increase is slightly more than general inflation which was 43% over the same period [4].
• The cost of a bath is now about 56p (depending on the size and depth of your bath), a typical shower 35p
• In 2015 this was 36p for the bath and 22p for the shower.
• When heating by gas the cost of the water is nearly 60% of the total cost.
• When heating the water by electricity, the cost of the water is only 33% of the total.

[1] How much does your bath or shower cost? (Energy thoughts and surprises)

[2a] Metered Charges (Cambridge Water)

[2b] Our standard charges (Anglian Water)

[3] What is the energy price cap? (Energy price cap unit rates and standing charges, (OFGEM)(cap as of August 2026)

[4] Inflation calculator (Bank of England)

What is Money And how to Make it Work Better for Everyone by Ray Galvin (Review)

 

First of all, some things I should mention.

• Ray is a good friend so my review may be considered biased.
• Although I am much better than I was I am still under par from my brain surgery, 18 months ago. (see Pause due to Head Injury ). So it is possible that I have not understood this book as well as I would have done under other circumstances.

Almost all of us use money and most of us think we have a clue about how it works if only how it can be earned and how it can be used to buy things we need or would like to have. However, some things are intrinsically pretty hard to understand. For example:

• What is money?
• What causes inflation?

Galvin goes a long way to answering these questions. Along the way he discusses taxation (should we tax income or wealth), crypto currencies and the role of government and central banks. 

Dealing with uncertainty in climate change risks

The inspiration for this post comes from a couple of reports from the Institute and Faculty of Actuaries.  [1] and also [2] about how climate change policy has often failed to evaluate climate risks adequately. 

 

Hemp for building insulation

It is illegal to grow hemp without a license as it is the plant source of cannabis, a class B drug. However the strains used for construction material do not contain significant amounts of THC. Historically hemp fibre has been used to make rope, sailcloth, parachute webbing and heavy duty clothing but recently it has been used as a natural insulation material and as a reinforcing fibre for concrete and plastic. It is even used in making body parts for cars (famously introduced by Henry Ford [1])

Other fibre crops can also be used such as flax and bamboo. However hemp is stronger than either [2].

Biodiversity and national security

 I recently read the government report ‘Global biodiversity loss, ecosystem collapse and national security’ [1]. This was published in January so I am a bit behind in getting to it. It makes for grim reading. The national security issues of concern include migration, conflict and competition for resources.

People’s Emergency Briefing

Last night (Saturday 18th April) I went to a showing of the film ‘People’s Emergency Briefing’ [1] at Pembroke College. I was a bit concerned this might turn out to be horribly alarmist but actually it was not overly negative - the facts are quite frightening enough - and the briefings included sensible actions we can take to reduce the impacts [1]. Do go and see it with your friends and family and consider supporting the campaign to get this shown on TV and get more MPs to see it (screening map here https://www.nebriefing.org/screening-map). The format of the film is friendly and non-technical. It is a bit like Gogglebox with clips of experts explaining the issues interspersed with reactions from a small panel sitting on a sofa.

I can’t say there was a great deal that was new to me but it did reinforce some important facts.

Life without electricity

I recently went to one of a series of talks (https://cambridge.resilienceweb.org.uk/) on the theme of resilience (a critical issue due to climate change increasing the frequency of severe weather) and yesterday I came across this report from the Royal Academy of Engineering [1] which gives a vivid picture of how Lancaster coped with a major power cut due to flooding in December 2015. This post gives a flavour of some of the problems described in the report. However, it was written a decade ago. Technology has changed a bit since then; below I have suggested some alternative solutions now available.