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What are the spots?carbon dioxide emissionsfuel costs They show the relative Cost Savings and Reduced CO2 emissions.

Money
Saving
Tips
 Energy 
Savings 
Each Year
 Money
Savings
Each Year
 CO2
Savings
Each Year
 Comments
dishwasher energy saving tips Dishwashers
Read More
30kWh -
90kWh
£4.62 -
£13.86

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11.01kg -
33.03kg
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Run the machine full and less often

boil less water in kettle energy saving tips Boiling Water
Read More
82kWh -
164kWh
£12.628 -
£25.256

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30.09kg -
60.19kg
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Boil only what you need. Savings depend on how much tea you drink!

fridge freezer energy saving tips Fridge Freezers
Read More
50kWh -
400kWh
£7.7 -
£61.6

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18.35kg -
146.8kg
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Fridge maintenance. Savings depend on size, age and rating

dmoney saving tips tumble drying Tumble Dryers
Read More
90kWh -
350kWh
£13.86 -
£53.9

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33.03kg -
128.45kg
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Operate Less often, clean filters, part dry clothes?

differnce in cost of shallow or deep bath Baths
Read More
700kWh -
1400kWh
£30.1 -
£215.6

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147kg -
513.8kg
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Have shallower baths and consider how you heat water

change energy supplier to save money Change Supplier
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0kWh -
0kWh
£0 -
£500

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0 -
0
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save money and have a beerSwitch! This is the single simplest way of saving money. This is equivalent to 100 pints of beer!

shower or power shower which is cheaper Shower of Power Shower
Read More
120kWh -
1100kWh
£18.48 -
£242

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25.2kg -
403.7kg
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Aviod immersion heated power showers

save money and energy with good loft insulation Install Loft Insulation
Read More
3000kWh -
3750kWh
£129 -
£161.25

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630kg -
787.5kg
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Modern loft insulation in a 3 bed semi - these numbers are for Gas, savings are greater for other fuels

save money and energy with good loft insulation Improve Loft Insulation
Read More
1000kWh -
1500kWh
£43 -
£64.5

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210kg -
315kg
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Modern loft insulation in a 3 bed semi - these numbers are for Gas, savings are greater for other fuels

This table is under construction there are more tips here.

Please use comments below or
twitter to ask a question.

Solar Hot Water

Last Updated on Wednesday, 05 April 2017 15:18





solar hot water costs and savings
 Cost:  High
 ROI:  11 to 62 Years (No RHI)
 Skill:  Specialist
 Energy Saving:  Medium
 CO2 Saving:  High
 How much this measure costs to install: Low : Medium : High
 ROI is the time it takes to return the investment in fuel savings for an average gas heated 3 bed semi-detached house and assumes no government incentive schemes are used: Years
 How easy this is to do: DIY-Easy : DIY-Skilled : Specialist
 How much energy will be saved with this measure: Low : Medium : High
 How much Carbon Dioxide emission will be saved with this measure: Low : Medium : High

What is Solar hot Water?

Before we start on what, we need to cover where. Solar Hot Water is used all over the world, it is very effective especially if you live in a warm country, this article is about the UK where solar hot water is much less effective option than in for example Spain. We also do not cover any grant schemes here (Renewable Heat Incentive, RHI), they are changed to often! With a grant scheme you will find that an installation will be more cost effective.

NB. We do not factor in any grant schemes here, at the moment the scheme it is the Renewable Heat Incentive (RHI), they are changed to often! With a grant scheme you will find that an installation will be more cost effective. Please refer to the energy saving trust for the latest.

The terms solar energy and solar power are often used to describe technologies which collect the energy of the sun and redistribute it for our use. These terms are however a little ambiguous. Solar energy effectively drives our whole planet, wind, wave and fossil fuels could ultimately be regarded as solar energy. For the purposes of this site our only concern is for solar energy that can be collected directly by our dwelling and used to, for example, heat water or to drive our electric devices. For this article on solar thermal only heating hot water is considered. Please follow the link to take a look at Solar Photovoltaic’s


Solar Photovoltaic’s...


If you are interested, all light is made up of photons, which might be best described as tiny little packets of energy. There is a whole range of different energies or “packet sizes” which if you put them all together from small to large would constitute the spectrum of light.

To collect this energy a method is required to collect photons of light and to convert the energy in this light into another form of energy for storage or use.

For domestic properties there are two main methods of collecting solar energy to heat water glazed flat plate collectors (thermal plate) and evacuated tube collectors (thermal tube), they both absorb the light energy and convert it to heat, the main difference with an evacuated tube system is that they operate in a similar way to a vacuum flask, the vacuum inside the tube collectors insulating the fluid against heat loss.

The light photons are absorbed by electron transitions in the material of the solar panel, these excited states decay releasing the energy as heat, this heat is conducted to a fluid in the panel.

Financially are they worth it?

Over a year in the UK the amount of solar radiation hitting the surface of the earth varies enormously, we all know that! At its peak it is about 8 kWh/m2 on the best day and 100 times less than that on the worst, i.e. 0.08 kWhm2. Taking into account the amount of useful radiation, i.e. the radiation that the thermal collector can convert to heat and heat loss factors a total efficiency of about 30 to 40% is generally accepted. This means that only 30% to 40% of the radiation falling onto the area of the panel goes into heating the water. The grapic shows light energy availiable across Europe assuming that a panal is optimally inclined at about 38 degrees and is south oriented.

map of solar energy across europe

A reasonable estimate for energy use to provide a family of four with hot water is about 10 kWh each day or about 3500 kWh per year, taking a few days off for holidays. So on a sunny day taking into account efficiency factors you would get away with a 4m2 panel to provide all your hot water, and on a dull winter day, you would require a 2600 m2 panel. The latter is clearly impractical, on space and cost grounds, and not forgetting heat loss! In practical terms for about one third of the year the heat output from a solar thermal system is zero in the UK. It is also fairly obvious that if you have, as in the example table below, a 6m2 panal an you use 10 kWh hot water each day, then you will not use all the potential of the system.

The graph just below shows the variation in light energy each day throughout the year for a point in the middle of England

solar energy throughout the year in the UK

Exact numbers are very difficult with solar because of the variability of the climate and personal use habits. But for a modest 6m2 thermal collection system costing about £5000 installed, optimistically you may get 25% of your annual hot water requirement from the system, for the family of four this is 750kWh. If you had used natural gas to heat your water, you would have saved £32.25 (157.5kg) , with LPG, £43.5 (172.5kg) and with standart tariff electricity, £115.5 (275.3kg) .

Not much, is it? If your system cost £5000 and your main fuel is LPG it would take about 50 year to pay back the investment, not including all the maintenance cost, and will it last that long? Money is not the whole story, the CO2 emission savings are pretty good (the numbers in brackets). But would it be your first choice to save money and reduce emissions, we would argue not. Insulate your loft or walls First.

The tables below gives more data with consideration for the different light levels in the UK, the further south you are the better. Well in terms of light levels. The value for the light energy availiable in these tables assume that the panal is optimally inclined at about 38 degrees and is south oriented. The table also assumes that all of the potential incident solar radiation is useful and this is probably not the case.


Data table for Solar Thermal Tube
Light energy avaiable to you see graphic above kWh/m2 per year 900 1000 1100 1200
Light energy incident on a 6m2 panel * kWh 5400 6000 6600 7200
Light capture efficiency, or Gross efficiency over full area of solar collector 50% 50% 50% 50%
Energy captured by the collector kWh/m2 per year 2700 3000 3300 3600
Working efficiency how much of this light energy converts to usable hot water 70% 70% 70% 70%
Energy converted to useable hot water kWh 1890 2100 2310 2520
Equivalent Price if you use Gas £81.27 (396.9kg) £90.3 (441kg) £99.33 (485.1kg) £108.36 (529.2kg)
Equivalent Price if you use Standard Electric £291.06 (693.6kg) £323.4 (770.7kg) £355.74 (847.8kg) £388.08 (924.8kg)
Equivalent Price if you use LPG £109.62 (434.7kg) £121.8 (483kg) £133.98 (531.3kg) £146.16 (579.6kg)
Indicative installed cost (£ ) 5000 5000 5000 5000
Payback period (years) if you use Gas 62 55 50 46
Payback period (years) if you use Standard Electric 17 15 14 13
Payback period (years) if you use LPG 46 41 37 34
Data table for Solar Thermal Plate
Light energy avaiable to you see graphic above kWh/m2 per year 900 1000 1100 1200
Light energy incident on a 6m2 panel * kWh 5400 6000 6600 7200
Light capture efficiency, or Gross efficiency over full area of solar collector 70% 70% 70% 70%
Energy captured by the collector kWh/m2 per year 3780 4200 4620 5040
Working efficiency how much of this light energy converts to usable hot water 60% 60% 60% 60%
Energy converted to useable hot water kWh 2268 2520 2772 3024
Equivalent Price if you use Gas £97.524 (476.3kg) £108.36 (529.2kg) £119.196 (582.1kg) £130.032 (635kg)
Equivalent Price if you use Standard Electric £349.272 (832.4kg) £388.08 (924.8kg) £426.888 (1017.3kg) £465.696 (1109.8kg)
Equivalent Price if you use LPG £131.544 (521.6kg) £146.16 (579.6kg) £160.776 (637.6kg) £175.392 (695.5kg)
Indicative installed cost (£ ) 5000 5000 5000 5000
Payback period (years) if you use Gas 51 46 42 38
Payback period (years) if you use Standard Electric 14 13 12 11
Payback period (years) if you use LPG 38 34 31 29

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+1 # solar heatingdavid Karniewicz 2014-01-29 13:01
If anyone is considering the choice between solar pv and solar heating,choose solar pv and fit a device that recognises when the pv sustem is exporting back to the grid and then feeds this surplus electricity through your immersion heater,free solar heating for an extra outlay of £500 for the device
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0 # Silicon SolarSunny 2013-04-22 16:19
Solar thermal energy id definitely worth it! No matter what part of the country you are from you can always save money by investing in solar thermal energy. There is a company called silicon solar and they now have offices on both the East and West coast and they have sold their products all across the country because they are simply the best and most high end solar manufacturer in the market. Definitely check out their website and take a look at their competitive prices!www.sili consolar.comwww .sunmaxxsolar.c om
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0 # Solar Thermal Calculations or potential YieldMatt 2013-03-31 16:01
Hi there,I'm enjoying looking around your excellent web site - however I'm interested to understand the calculation parameters you've used to calculate the Solar gain. The figures suggested in Energy converted to usable hot water in kWh are considerably higher than in any SAP calculation in fact the figures mentioned above would almost certainly be unachievable according to SAP for any standard twin coiled hot water cylinder. Therefore if possible would it be possible to see the calculations behind the figures above?We are currently going for SAP Appendix Q recognition with our unique and patented Solar 3C solution and are in regular communication with BRE regarding low temperature heating with Solar Thermal, so if possible I would very much welcome chatting through the benefits of Solar 3C and how it may add clarity to the Solar Thermal/PV tables plus it may change the negative downward thumb to a positive thumbs up in terms of payback.Histori cally and as confirmed by BRE, Solar Thermal has always suffered from the restriction of the medium used to hold the energy collected and then in the vast majority of cases this is only used for hot water via twin coil cylinders. Thermal Stores accept solar energy however due to their very high standing temperatures (just to be able to deliver any useable hot water) the solar contribution annually is virtually worthless.Solar 3C is different - it's a 3-coiled unvented hot water cylinder (2 input coils middle & bottom + 1 output coil at the top) any/all spare energy instead of either sitting in the cylinder all day doing nothing or slowly passing through the cylinder wall (heat loss) can be used to contribute towards space heating. By way of an example, if there was just 35degrees available on the roof/at the thermal collector, this would roughly equate to a maximum achievable cylinder temperature of around 31degrees C not hot enough for washing, bathing or showering however ideal for use with an Underfloor Heating system - therefore in this example when there would not have been enough energy to provide hot water and where the cylinder would require a back-up source to top up the temperature it would have been able to contribute potentially all day to the UFH and providing space heating (end users largest energy consumption costs) - at the end of the in this example the back-up souce would still be required to top up the cylinder for hot water just as it would have had the energy available on the roof not been used for space heating. Solar 3C therefore extends the annual window of solar yield significantly especially when installed in New Build properties with Underfloor Heating - Solar 3C would contribute more to the space heating than it could ever do for hot water because of the cooler running temperatures required for the UFH. Solar 3C is not limited to UFH because the weather compensator that makes up the Solar 3C controller will call for low grade or temperature heating even when installed with radiators or indeed in a retrofit heating system.The use of Solar 3C is extended further by the use of the ImmerSun switch whereby any Solar PV export is sent to an immersion heater (instead of being exported back to the national grid) this energy can then either be used to pasteurise the cylinder helping to protect against legionella or be used directly for space heating rather than just hot water - this potentially trebles the value of the PV export. With all of the above in mind I would very much welcome the opportunity to chat through the figures in your Solar chart and see if we can change the negative down pointing thumb for Solar Thermal to a positive THUMBS UP?? Just as hot water cylinders have evolved through time, from 0 coil (direct) to 1 coil for just boiler and no Solar, 2 coil boiler/heat pump and solar but no space heating to, 3 coil boiler/heat pump and solar PLUS space heating!! It's as obvious and easy as 1, 2, Solar 3C!!Thank you in advance for taking the time to read the aboveMatt (m 07850 741213)www.sola r3c.com
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