Heat pump technology is an attractive proposition for those looking to lower their energy bills. The only downside seems to be that it’s powered by electricity.
Unless you have access to a reliable supply of renewable electricity, you are obliged to plug heat pumps into the mains, and mains electricity is both expensive and carbon intensive. The same goes for mechanical ventilation and heat recovery (MVHR) systems.
There are two recent events that have brought the limitations of mains eco powered appliances home to me.
The first was a client who had specified a MVHR system, but removed it after the Standard Assessment Procedure (SAP) calculations had been completed. I feared that removing a piece of eco technology would have a detrimental effect on the SAP result. However, the revised score improved by one point because of the reduction in carbon-intensive mains electricity consumption.
The second concerns an eco development in West Bowling, Bradford completed in July 2011. From what I’ve read 33 out of the 45 homes built were to Level 4 of the Code for Sustainable Homes (CSH) and each had an air source heat pump (ASHP) installed. These houses were marketed as ‘super insulated’ with the promise of lower energy bills.
In reality, average bills at the development have been around £2,000 a year (the average yearly energy bill for a UK family home is £1,261). The culprit was increased mains electricity usage from their ASHPs. Residents say they are struggling to cope because it is too expensive to live there.
Mains gas may be a fossil fuel and just as volatile in terms of prices, but it is still cheaper than mains electricity and far more efficient. A cubic metre of gas entering the pipe at one end still comes out as a cubic metre at the other end.
Electricity is barely 25% efficient after transmission losses and has a vast carbon footprint. What’s more, it still costs around three times more than gas. If shale gas fracking goes ahead, then supply is assured for decades to come.
So, if you want to go down the ASHP route then don’t let me stop you, but my advice is always to use mains gas if you have it.