28 Jun 2010

Heat Pumps: troubling times

If you were to sit down and look for business ideas where there seems to be explosive growth potential, I reckon that heat pumps would pretty quickly bubble up towards the top of most peoples' lists. It's not exactly a new technology, having been around in one form or another since the 1950s, and in some territories (I'm thinking Sweden here, and maybe Switzerland) it's established as the No 1 method of providing home heating. But in the UK, it has been and remains distinctly fringe.

Now this is all set to change with the introduction of the Renewable Heat Incentive (RHI), about which I have blogged several times. The RHI promises to throw large dollops of money at people who choose to install heat pumps. Large dollops. Like enough to pay for the entire heat pump, and a good chunk of the running costs as well. Whether the RHI is a good thing or a bad thing I won't go into here, but what is indisputable is the RHI has the power to turn the home heating market upside down and make heat pumps No 1 here in the UK in a very short space of time. Which is its intention.

But right now, heat pump suppliers are having a very difficult time, because the RHI remains a consultation document and since it was launched earlier this year there has been a change of government and the new government has been very quiet (OK — completely silent) about its fate. At a time when new cuts are being announced on a daily basis, there is concern in the industry that the RHI won't see the light of day, even though the funding for it was due to be taken from our gas bills, rather than directly from the Treasury. The RHI consultation document signalled that the new subsidies would come into effect in April 2011, and that people purchasing heat pumps now would be be able to receive the payments as and when they become available. But it was only a consultation document......

So what has happened is entirely predictable. Heat pump suppliers now have interest in the product racing ahead at record levels, but no one is actually placing any orders because they are all waiting to see if the RHI is going ahead or not. So, far from booming, business is going backwards rather fast. It's nail biting time.

And against this difficult background, I keep hearing reports of unsatisfactory heat pump installations where either the heat pump fails to provide adequate levels of heating, or the electricity bills turn out to be way higher than was anticipated. Some manufacturers are getting mired in disputes with unhappy customers, and the nascent industry risks getting dragged down by adverse publicity before it's got off the ground.

It's not that the heat pumps themselves don't work. The failures seem to stem from two areas: one is that the houses in question are not nearly as energy efficient as they were designed to be, the other is that the collecting fields on ground source heat pumps are often too small, or that the ground conditions are too dry for the ground loops to work well. The first error is the fault of the builder, whilst the second is the fault of the heat pump installer, so you can guess how the blame is attributed when a dispute arises. It's messy.

When a plumber installs a conventional gas or oil fired heating system, they build in a huge margin of error. Because the additional capital costs of a larger boiler and larger radiators are not that great, it's no great cost to the plumber, and its worth it to prevent any potential disputes with unsatisfied clients. But heat pumps, especially ground source heat pumps, are expensive beasts (typical installation costs are upwards of £12,000) so there is a temptation to engineer their output far more closely to the designed demand, hence a much greater likelihood of the finished installation failing to deliver on expectations.

To avoid these problems, my suggestions would be:

• Make sure you are comparing like with like when looking at the quotations you get. Look at the heat output side of things. Don't just accept the supplier's word that their designed output will be adequate. Ask to see the calculations and ask what the margin of error is.

• Get a soil sample analysis carried out if you are going for a ground source heat pump. Tim Pullen tells me that the seasonal difference in heat draw between a dry, sandy soil and a wet, clay soil is huge - like 10w/m2 v 40w/m2. Some suppliers take this into account, many don't.


  1. Wet vs dry ground - it's not just heat transfer, which shd be better in wet ground than dry. It's also an indicator of the ground's ability to recharge itself with heat as it's taken out - either concurrently with extraction, or on a recuperation basis over the summer. If wet ground implies a flow of water, either horizontally, or vertically by rise and fall of water table, then heat will be imported with the water flow. It the water's non-moving then that won't happen. If the ground's dry it won't happen. In the latter two cases the only way that heat can recharge is by thoroughly uinatural conduction down from the surface - on average, natural heat flow is at least slightly the other way, outward. Inward heat flow can only happen when and because soil temp is held unnaturally at a colder temp than the surface - AKA freezing the ground your house sits on. No amount of good design can alter that basic fact, merely reduce it. I don't think the heat pump industry has its hgad round these very basic factors.

  2. Mark BennettJuly 01, 2010

    Tom is right in principle, but you also have to take into account where the water flow is coming from. If all your "upstream" neighbours also end up with heat pumps, the water could easily be very cold by the time it gets to your plot.

    In this era of very dense housing and small gardens a mass adoption of GSHP could easily lead to many systems that are initially OK, but that perform increasingly poorly as adoption increases.

    Do any GSHP designers take that into account at the same time as they take soil conditions into account?

  3. Methinks that even if it's still a consultation document, it would still make sense to be in the market just when the demand explodes :) Just so you could be ahead of the pack

  4. Good post. I have a heat pump for my house. Very useful.