ENVIRONMENT
Save money
Estimate calculation, water heating cost, four person 5 years:
Energy used to heat water is calculated according to the formula
Q = m * cs * (Tu-Tr)
Q = energy used
M = litres of water to be heated
cs = 1 cal/(g ºC) i.e. one calorie need to be used to increase the temperature of
one gramme of water by one degree. 1 cal = 4.186 j.
Tu = hot water temperature in use
Tr = water temperature within the public network
Assuming: each person uses 50 litres of water per day at temperature of 45°C water
temperature of the public network is considered to be 15°C
Q = 50kg * 4.186 kj/kg *30°C = 6.279 kj = 1.74 kWh
Assuming: 90% efficiency of the electric element: 1.933 kWh
Costs per kWh incl. taxes and indirect charges: 0.088 €
Daily costs per person 1.933 * 0.088 0.1701 €
Monthly costs per person 0.17 € * 30 5.1031 €
Yearly cost per person 0.17 € * 365 63 €
Yearly cost for 4 (family) persons per year 252€
| |
Convention electrical
|
Solar system
|
Purchase cost
|
150€
|
1500€
|
Installation
|
50€
|
350€
|
Subsidy
|
0
|
451.5€
|
Yearly cost
(four persons)
|
252€
|
75
|
After 5 years
|
1460€
|
1473.5€
|
After 6 years
|
1712€
|
1520€
|
After 7 years
|
1964€
|
1595€
|
|
Cost comparison between convention electrical water heater and solar system: