Heat pump case study

This is a case study of the heating of a 2 bedroom 100m² house in Auckland.

The period of this study is for the 12 months from July 2010 to June 2011.

During this time the house was heated by a couple of free standing electric oil filled radiators. There were 4 months of the year where the heaters were not used at all. These were the months December through to March. During the months of June and July the heaters were used the most and were using on average 20 units of electricity a day. From the months of August through to November the use of the heaters diminished and the average daily consumption for this period was 10 units. From the months of April through to May the daily use increased and the average daily consumption for this period also amounted to 10 units.

The winter during this period was a relatively mild one due to the large amount of rain. Wet winters result in mild winters.

During the study period the cost of electricity at current prices amounted to 23.09 cents per unit (11.13c Mercury, 8.74c Vector, 0.21c Electricity Commission levy, 3.01c GST).

The total electricity consumption for electrically heating the house over the case study period was 3,359 units for a total cost of $775.59.

To generate the exact same amount of heat over the study period using a heat pump would have cost a quarter of this amount. This means that for this house there is the potential to make an annual saving of $582 if they switch from their current oil column heaters to a heat pump.

To install a heat pump for this particular house would cost $2400. It would take 4.1 years to pay for itself and from then on this home would be better off by $582 every year.

4 years makes good investment sense but the situation gets even better if we look at what has been happening to electricity prices. For the five years leading up to start of the study period the price of electricity doubled. There is every reason to believe this trend will continue if not accelerate due to the ever increasing demand for electricity and the fact that the power supply companies need to invest in more generating plant and that this new plant will not be able to generate electricity as cheaply as the existing hydroelectric dams of this country.

If we factor this doubling of electricity prices every 5 years into our equation then we get a payback period of 3.2 years.

Year	Total Saving at today's prices	Total Saving at adjusted prices based on last 5 years of price increases
Year 1	$582	$582
Year 2	$1164	$1280
Year 3	$1746	$2118
Year 4	$2328	$3124
Year 5	$2910	$4331