Friday, March 21, 2008

Cost-effective ways to reduce your carbon footprint

I'd like to highlight Sandy Polak's
page on how to be green
. It is the best page I've read on this topic. The main thing I would have amplified more than Sandyis heat pumps: I bought a 'green' condensing boiler a few years ago, and now regret having done so - I wish I had looked into air-source heat pumps. Condensing boilers are not green: they use fossil fuels! I reckon that, even if electricity is produced from gas-fired power stations, air-source heat pumps are a good thing, environment-wise; and if and when the grid is decarbonised, heat pumps will get ever greener. Heat pumps have to be the future for domestic heating without carbon.


Unknown said...

Thanks for your vote of confidence. I completely agree that heat pumps are a good (maybe the only)solution in the long term, but while the UK electricity is still 70% fossil-fuel based, the CO2 merits of heat pumps are not all that stunning, and the operating costs are higher than gas central heating. Hopefully the picture will change in the future. In the meantime my webpage concentrates on Cost-Effective ways of reducing CO2, and heat pumps are not yet high on the cost-effectiveness criterion.
Keep up the good work!

Robin Smith said...

I recently did some research on the true costs of renewable power (not quite finished) and part of that led me to a seminar on renewable heat. They too convinced me that heat pumps are far better than solar and wind in any form. And at first sight nearly as good as gas but not quite. But over the lifetime could be better both in cost and CO2 terms. (they claim CO2 per kWh of heat is already better but they are selling them, (210/120gco2/kWh gas/heat pump))

Keep an eye out here

Compost John said...

Heat pumps can be a bit better energy-wise if their electric pump power is from renewables, such as having your bill paid to Good Energy Ltd, or if you're really well organised (and wealthy!) PV panels and a bank of batteries....

Remember too that heat pumps can act as an air conditioning system, ie they take the heat out of the floor and dump it in your hot water tank, so you can have a cool house and a hot shower....

John 'CRAGger' Cossham, York, UK

tom.harrigan said...

I have never found a heat pump installation that actually operates any where near the advertised COP. Perhaps someone can point me in the direction of one? I generally find that a COP of 2 is what people actually get, occasionally 2.5. At this level there really is no point in them whatsoever. They are also extremely expensive, particularly if you add on the ancillaries like under floor heating. I am certainly not convinced there is any point in providing hot water with one!

Unknown said...

Hi Recyclist,
You quote COP of 2.0 to 2.5 as an actually achievable figure. This is much as I suspected (always sceptical of sales claims!). Do you have any measured data available to support this, as I would like to include it in my article " Cost-effective ways to reduce your carbon footprint". I have also heard that some heat pump systems include effectively an immersion heater to boost the hot water output to a useable temperature. Can you comment on that? Heat pumps are great in principle, but not yet a mature technology?
Contact me on

Mark Brinkley said...


I really think you need to do some more work on heat pumps before you write comments such as

" the best air-source heat pumps (which require just a small external box, like an air-conditioner ’s) can deliver hot water to normal radiators with a co-
ef´Čücient of performance above 3."

The quoted CoPs of heat pumps are for lifting temperatures just 35°C. For every 1°C above this, heat pumps loose around 3% of their efficiency. Normal radiators require a water temperature of 80°C: that's atypical uplift of 70°C.

You do the maths! At this level a heat pump is no better than electrical resistance heating.

Where heat pumps can work well is with low temperature underfloor heating, but that is rarely a sensible option for anything other than new builds.

Anonymous said...

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