Currently Gas prices are approximately 4.5 pence (£0.045) per kWh of energy used.
Let us assume that a 4 person household has decided they have Average Consumption values of 50 litres of hot water per person per day. They also say that they use the dishwasher (20 litres of hot water per cycle) and washing machine (30 litres of hot water per cycle) twice a week and the temperature of the hot water needs to be 45 degrees Celsius. Therefore we can calculate that their Hot Water Requirement is:
DHW Requirement (DHWr) = 4 persons x 50 litres (@ 45 degrees) + 16 litres (@ 45 degrees)
DHW Requirement (DHWr) = 216 litres (@ 45 degrees) per day
From this, we can use the following equation to get the Hot Water Power Requirement (DHWpr):
DHWpr = 216 x 1.16 x (45-4)
DHWpr = 10272Wh per day
DHWpr = 10.3kWh per day
Therefore, our house is spending the following on Domestic Hot Water Heating:
Annual Cost = £0.04 x (10.3kWh x 365 days) = £150.38
Let us then assume that they install a Solar Thermal system at a cost of £3,000 fully installed. The system has an efficiency of 70% and will therefore provide 70% of their annual Hot Water needs. Thus, we can calculate their annual savings as being:
Annual Saving = £150.38 * 70% = £105.27
This alone gives a very small ROI of 3.51% and a payback period of nearly 28.5 years!!!
However, let us now add in the Renewable Heat Incentive payment of £0.08 per kWh. This payment is made for every kWh of energy generated through the Solar Thermal system. The Solar Thermal system produces 70% of your annual needs:
Annual Energy Production from Solar Thermal System = 10.3kWh x 365 days x 70% = 2631.65kWh
Annual Payment from RHI = 2531.65kWh x £0.08 = £210.53
Total Annual Saving = RHI Payment + Saving from reduced energy bill = £210.53 + £105.27 = £315.80
Total ROI = £315.80 / £3,000 = 10.53%
Payback period = 9.5 years
Funnily enough, this is very similar to the ROI and Payback Periods achieved with Solar PV systems, and represents a very good investment (note that they payments are income tax free and inflation linked to the RPI).
Home Pages of interest:
- Visit the Solar Thermal home page
- Visit the Energie Solar home page
- Visit the Solar Thermal and Swimming Pools home page
Other Pages of interest in this section:
- What is Solar Heat Power?
- How Does Solar Thermal Work?
- Types of Solar Thermal Systems
- Flat Plate versus Evacuated Tube Collectors
- Annual Energy Production
- Components of a Solar Thermal System
- Costs of a Solar Thermal System
- Servicing and Warranty
- Solar Thermal Financials and Paybacks
- Our Products
- Solar Thermal and Swimming Pools
