There are cases where the costs of running a new boiler are higher that the costs of running the old boiler.
I will ask for permission to quote.
Regret I was only given permission to post this meagre amount of information.
The test bed is 22 semi-detached houses, ( 11 identical pairs of 2 bedroom houses ) owned and maintained by a large industrial organisation for staff and long term visitor accommodation.
Gas , electricity and water are supplied to the houses by the organisation
Historically gas , electricity and water meters have been read monthly and this data is archived,.
Four houses were converted to un-vented DHW and sealed heating with pumps and valves gear external to the boiler.
Four houses were converted to combination boilers.
Fourteen houses retained the vented DHW and vented heating system
Four graphs of gas consumption during the 16 months after the conversions were produced ,
(1) Mean of 10 of the unconverted houses
(2) Mean of the other four unconverted houses
(3) Mean of the houses converted to un-vented DHW
(4) Mean of the houses converted to combination boiler
Analysis of the graphs
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An analyst, un-aware that the graphs were of gas consumption, made the following observations
Graph (1) as requested was used as the benchmark for comparison with the other grpahs.
Graph (2) practically the same as the benchmark graph.
Graph (3) was similar to the benchmark graph, deviations ( per month ) from benchmark were between +1.5% and -5.2%
Graph (4) was similar to the benchmark graph, deviations ( per month ) from benchmark were between +7.8% and -4.6%
The highest deviations from the benchmark were in the summer months.
Residents Survey
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Residents in houses converted to un-vented DHW were generally satisfied with the new system.
Residents in two of the houses converted to combination boilers had since the conversion been using electric kettles for washing up water.
Possibly use of electricity for heating water.
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Graphs of gas and electricity consumption were produced for each of the houses converted to combination boilers. These graphs covered the 16 months of the trial and 16 months preceding the conversions These graphs demonstrated that after conversion two houses were using more gas per month in summer than the other two houses (B and D). The graphs of electricity used demonstrated houses B and D used slightly more electricity than houses A and C in the summer months.
When the analysts were made aware that the graphs were of gas and electricity consumption they expressed concern that factors such as cooking methods and life styles would reduce the validity of any conclusions drawn from the graphical data. The inference that DHW from a cylinder was prefereable to DHW from a combination boiler was however valid based on the data avaiable.
The opinions of the residents affected by the conversions were taken into account and the decision was made to convert all the houses to un-vented DHW.
