Hi, we are about to install gas CH and would appreciate some help in estimating the running cost.
We have a gas water heater at present and so are looking at changing to a condensing combi boiler and adding radiators (under floor heating is not possible in our case)
I guess a typical timing configuration is 2hrs before we get up and 3hrs when we get back in the evening. I calculate heat loss at 20,9kw and propose a an initial additional startup load of 20% for 30mins (ie the time taken to raise the temperature of the pipes and radiators to steady state)
So maximum daily energy needs are (2+3 hrs) * (20,9 + 2,1 * 2kw) =108,8 kWh/ day. Does this seem reasonable?
The local climate is fairly mild and based on actual bottled gas convection heater use, we can estimate % of max heat loss which will occur in January:
% max Days
Oct 10% 31
Nov 50% 30
Dec 80% 31
Jan 100% 31
Feb 80% 28
Mar 10% 31
So, take the max daily energy requirements, multiply by % and number of days and I get 10785,5kWh total annual heating requirement. So far so good?
The condensing boilers we are looking at are rated as 98-109% efficient, so can we assume that on average at least 100% of the energy burnt is converted to heat transferred to the radiators? If so, does that make the price per kWh of gas the cost of annual energy requirements?
ie Annual cost = 10785,5kWh + 0,05 euros/ kWh = 585 euros + fixed costs + VAT?
thanks in advance for any input
We have a gas water heater at present and so are looking at changing to a condensing combi boiler and adding radiators (under floor heating is not possible in our case)
I guess a typical timing configuration is 2hrs before we get up and 3hrs when we get back in the evening. I calculate heat loss at 20,9kw and propose a an initial additional startup load of 20% for 30mins (ie the time taken to raise the temperature of the pipes and radiators to steady state)
So maximum daily energy needs are (2+3 hrs) * (20,9 + 2,1 * 2kw) =108,8 kWh/ day. Does this seem reasonable?
The local climate is fairly mild and based on actual bottled gas convection heater use, we can estimate % of max heat loss which will occur in January:
% max Days
Oct 10% 31
Nov 50% 30
Dec 80% 31
Jan 100% 31
Feb 80% 28
Mar 10% 31
So, take the max daily energy requirements, multiply by % and number of days and I get 10785,5kWh total annual heating requirement. So far so good?
The condensing boilers we are looking at are rated as 98-109% efficient, so can we assume that on average at least 100% of the energy burnt is converted to heat transferred to the radiators? If so, does that make the price per kWh of gas the cost of annual energy requirements?
ie Annual cost = 10785,5kWh + 0,05 euros/ kWh = 585 euros + fixed costs + VAT?
thanks in advance for any input