Site Prices Update
Last Updated28th June 2022
All calculations on this site are based on current fuel prices, they are checked regularly and calculations are automatically updated.
The costs calculated based on these fuel prices should be regarded as 'good estimates', given that fuel prices vary in different parts of the county and at different time of the year.
The calculations also have different levels of accuracy depending on the nature of the calculation. For example calculating the energy use of a known power output TV is very easy compared to calculating the effect on energy savings when insulating a cavity wall.
Site Calculations
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At Confused About Energy we aim to provide practical, impartial advice on all aspects of energy usage, climate change and ways to save money on energy bills.
All calculations on this site are based on current fuel prices they are checked regularly are automatically updated and were last changed on:-
28th June 2022
The costs calculated based on these fuel prices should be regarded as 'good estimates', given that fuel prices vary in different parts of the county and at different time of the year.
The calculations also have different levels of accuracy depending on the nature of the calculation. For example calculating the energy use of a known power output TV is very easy compared to calculating the effect on energy savings when insulating a cavity wall.
Site Calculations
| Electricity | £0.271 per unit (1 kWh) |
| Economy Electricity | £0.094 per unit (1 kWh) |
| Gas | £0.072 per unit (1 kWh) |
| Domestic LPG | £0.122 per unit (1 kWh) |
| Heating Oil | £0.104 per unit (1 kWh) |
| UK Grid CO2 Emissions | 0.233 kg per kWh used |
The main units used in this site are in the table below, For a complete explanation of power and energy Read More.
| Unit | Name | Detail |
|---|---|---|
| W | Watt | Unit of Power |
| kW | Kilowatt | 1000 watts |
| kWh | Kilowatt hour | Measure of Energy |
| L | Litre | Measure of Volume |
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Comparing the costs between deep and shallow baths with gas and electric immersion heating.
Money Savings range you could have employing this measure.
Carbon Dioxide emission range that could be saved with this measure.
How much does it cost to have a bath?
The main costs involved in washing yourself relate to the cost of heating water and bathing uses a lot of hot water.
Gas, electricity, solar energy or solid fuels like coal can all be used to heat water in the domestic environment. Solar water heating and solid fuels are considered in more detail in separate articles. To make the comparison between deep and shallow baths only gas and electric immersion heating are considered.
There is a wild variation in bath size, preference on how full you like to have a bath, the temperature of the water you prefer and indeed the temperature of the water coming into your property. All of these factors will influence how much it costs you to have a bath. The examples shown below are a 100 litre, a 150 litre and a 200 litre bath volume with a bathing temperature of 40oC and an incoming water temperature of 10oC. 100 litres would be a relatively shallow bath and 200 liters quite deep for most of us.
| Modern Gas Boiler | Electrical Immersion Heater | |
|---|---|---|
| Small (100 litre) | £0.314 (0.7kg) |
£1.05 (0.8kg) |
| Medium (150 litre) | £0.471 (1.1kg) |
£1.575 (1.2kg) |
| Deep (200 litre) | £0.627 (1.5kg) |
£2.099 (1.6kg) |
| Modern Gas Boiler | Electrical Immersion Heater | |
|---|---|---|
| Small (100 litre) | £114.626 (267.5kg) |
£383.503 (296.8kg) |
| Medium (150 litre) | £171.923 (401.2kg) |
£575.2 (445.1kg) |
| Deep (200 litre) | £229.121 (534.6kg) |
£766.566 (593.2kg) |
The conclusion is obvious here if you can avoid it do not use an immersion heater to heat your bath water, it is expensive, although there are immersion heaters that operate on ecomomy 7. It is also clear that you could save considerably by just having shallower baths, more difficult to do in the cold winter months!
Do your bath volumes allow for occupant displacement?
I displace well over 100 litres; my wife and teenage son each well under 50 litres.
So my "full to the overflow" quite deep old cast iron bath is not much over 100 litres of hot water - a fact cross checked by our 117 litre hot water tank needing to be run to cold but not much more to fill it from only the hot tap.
How much extra energy do I use to warm up old thick cast iron compared to modern plastic? Non-trivial I think.
we had the old sytem, gas boiler heating hot water tank and radiators. New system meant siting new boiler in utility, heating is much improved, BUT hot water system in quite inferior to old system. I could;nt recommend this new hot water system to anyone!!!
Hi, am having a combi boiler fitted, wonder what the average boiler hot water temperature range should be to give a comfortable bath/ shower, as have a old system with copper hot water cylinder at present. thanx for any info
Hi interesting article ! Can you show your calculation so that I can add the rate I am buying gas from my provider to see what a bath costs ! Rees
does this help?? T1 = temp of cold water (K), K is Kelvin T2 = temp of hot bath water (K) V = volume of bath water used (litres) S = specific heat capacity of water = 4.18 J/cm3/K energy to heat the water is therefore Ej = S*(T2-T1)*V*1000 the 1000 to get units in Joules to factor in boiler efficiency (Beff in percent, 90% probably) Eb = Ej (1 + (100-Beff)/100) 1 kWh = 3600000 Joules convert to kWh Eb (kWh) = Eb/3600000 cost to heat bath per bath = Eb (kWh) * Cost per kWh
given the ever changing (always increasing!) cost of gas and electricity, can you add a note to show when these calculations were done.
All the calculations on this site are based on one variables file which is updated each year. The last update was in May 2010. All the calculations on the site will change when this file is updated in a few weeks. The current rates are shown on the home page in the bar chart, this is also updated in the same way. perhaps I should add this date to each calculation? All the best richard
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