Earnings & Savings

Solar Thermal

Savings & Cash Flow Analysis

Assumptions

  • Gas prices of 4.5 pence (£0.045) per kilo watt hour of energy
  • Property with 4 people
  • Average hot water consumption of 60 litres per person per day
  • Dishwasher of 20 litres of hot water at 45 degrees per cycle four times per week
  • Washing machine of 30 litres of hot water at 45 degrees per cycle three times per week

Therefore we can calculate that the Hot Water requirement is:

Hot Water required:

4 persons x 60 litres = 240 litres
+ (20 x 4)
+ (30 x 3)
= 170 litres / 7 = 24.2
= 264.2 litres per day

From this, we can calculate their daily Hot Water “Power” Requirement:

= 240 + 24.2 = 262.2 x 45 = 11,889 per day
= 11.9 kilo watt hours (kwh) per day

Therefore, the cost to power their hot water is:

£0.04 x (11.9kwh x 365 days) = £195.45

If:

  • The house has a Solar Thermal system at a cost of £4,000 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 = £195.45 * 70% = £136.82