EcoRenovator - View Single Post - How much energy to heat 100 liters of water?

bernard · 10-13-15, 07:47 AM

Thank you for sharing the link Steve. That is a very interesting page.
But I still do not understand it.

If efficiency (EF) of electricity is 100% (or 1.0), then in order to calculate the amount of electricity needed to heat 100 liters of water by 35°C, we have:

a) electricity:
volume * (deliveryT-mainsT) / EF
100 * (45-10) / 1.0 = 3500 kcal
3500kcal / 860 ≈ 4 kWh (13.6 kBtu/h)

Natural's gas efficiency is lower than 1.0. I found this table:
View image: fuel type efficiencies

Let's assume that we chose the natural gas instantaneous fuel type: EF = 80% (0.8). In that case the amount of energy needed to heat 100 liters of water by 35°C would be:

b) natural gas
volume * (deliveryT-mainsT) / EF
100 * (45-10) / 0.8 = 4375 kcal
4375kcal / 860 ≈ 5 kWh (17 kBtu/h)

But 5 kWh of what? Not an electric energy, but what? Thermal energy?
How can I compare 4 kWh of electric energy with 5 kWh of Thermal energy?

10-13-15, 07:47 AM	#3
bernard Lurking Renovator Join Date: Sep 2015 Location: Hungary Posts: 22 Thanks: 9 Thanked 0 Times in 0 Posts	Thank you for sharing the link Steve. That is a very interesting page. But I still do not understand it. If efficiency (EF) of electricity is 100% (or 1.0), then in order to calculate the amount of electricity needed to heat 100 liters of water by 35°C, we have: a) electricity: volume * (deliveryT-mainsT) / EF 100 * (45-10) / 1.0 = 3500 kcal 3500kcal / 860 ≈ 4 kWh (13.6 kBtu/h) Natural's gas efficiency is lower than 1.0. I found this table: View image: fuel type efficiencies Let's assume that we chose the natural gas instantaneous fuel type: EF = 80% (0.8). In that case the amount of energy needed to heat 100 liters of water by 35°C would be: b) natural gas volume * (deliveryT-mainsT) / EF 100 * (45-10) / 0.8 = 4375 kcal 4375kcal / 860 ≈ 5 kWh (17 kBtu/h) But 5 kWh of what? Not an electric energy, but what? Thermal energy? How can I compare 4 kWh of electric energy with 5 kWh of Thermal energy?