A Retro fit Installation of a Heat Pump

A retrofit installation of a heat pump is most cost effective for those with oil fired heating, as recovery times for capital outlay are a lot shorter due to the savings made with a heat pump system against the price of oil. That said, with the rocketing prices of gas and electricity installing a heat pump can still make economical sense over a slightly longer term.

The viability of installing a Heat Pump to an existing oil fired home depends on the delivery system of heating in your home (22mm core pipe and radiators), insulation properties of your house (Double glazing/ 12"loft insulation etc.) and how much you spend on oil a year (2K?). Ground source heat pumps don't produce high temperature space heat like an oil boiler, but very effective, lower temperature heat for longer periods. If your home is poorly insulated it doesn't work well, the house will stay cold and the boiler will run all day, proving very costly.

With all costs weighed into the balance against the idea of having to upgrade any of the above, if you are spending enough on oil it may still be viable to upgrade the insulation and radiators and install a heat pump because the pay back on capital expended is realistic (inside 10 yrs).

If you are paying around £0.65p/l for oil, the theoretic translation of that into energy, is about £0.09p/kw of energy from oil. Factoring in the losses in efficiency from an average combustion boiler which is generally about 75% of the oil you burn turns into heat.. You are then looking at a cost of £0.1125p/kw, for heat leaving your boiler.

Comparing oil to electricity, we are paying anything up to £.09p/kw for electricity at the moment. A ground source heat pump delivers 400% of the energy you pay for, as heat. So your £0.09p/kw electrical energy cost becomes £0.0225p/kw cost of delivered heat. This is because the "heat" collected is free out of the ground, but the cost incurred is in having to pump the solution through the ground and a heat exchanger with gas, compress the gas to extract the heat and pump the heated water around your home.

An average system would cost very roughly about 8 - 10K installed and cost about £500.00 a year to run. If a home is using 2k a year to heat with oil they would save £1500.00 a year towards recovering the capital within 5-6 years. These are only rough figures but are not unrealistic and make no allowance for other factors like interest charged on the capital, nor further increase in the cost of oil.

Generally on a retrofit, we would prefer to leave the existing boiler in for a year, alongside the new one and measure any oil used up in that year. The reasoning for this is, houses which are not built to the newest building regulations are very difficult to accurately calculate heat losses from.

The Heat Pump is sized on an estimated heat loss calculation for the building and the risk is that if this is not accurate to within tolerances, the Heat Pump will stay on continuously at great expense or short cycle because it is producing too much heat for the house to absorb. Having the old oil boiler in line provides a back up against an undersized boiler and cold home. It also allows the home owner to use up the remaining oil by turning off the Heat Pump before removing the old oil boiler and tank once the system has been proved to work.

Some of the secondary benefits are no CO2 emissions, 20-25 year life on the boiler, no annual servicing, added re-sale value to the home and no noise and  smell from a combustion boiler.