Changing whole house heating

AdrianC

thenudeone wrote: »

Although bottled gas is about a third more expensive than oil, which is itself around 50% more expensive than mains gas, so definitely not a low-cost option.

I'm not referring to bottled gas. I'm referring to a bulk tank - 1200 litres in our case - which works out MUCH cheaper than bottles. We pay IIRC 48p/litre (a quick google suggests 6.6KWh in a litre, so just over 7p/KWh), plus about 12p/day for tank rental.

Robwiz

I have been looking at biomass too. It appears to me that a few people have been unfortunate with poorly designed or installed systems and they have been very vocal online about their problems. The same is true of air to water heat pumps – often people living in social housing who had an ashp imposed against their wishes.

From what I've read, the key points about biomass are:
-a local, dependable installer is the most important consideration as the system will need servicing and support for 20 years.
-people with log burning boilers tend to be satisfied but there's a need for a lot of storage space for logs (or briquettes which are as cost effective as pellets).
-the biggest problem area experienced is correct sizing and installation of accumulator tanks (lots of examples of them being plumbed in incorrectly).
-most suppliers attempt to sell the most expensive/complicated boiler they can, using the RHI to cost-justify a high outlay. In my view the customer should enjoy the government incentive, not the installer.
-people with less expensive boiler (e.g. MCZ) are satisfied.
-MCS approved boilers are marked up by between 50% and 100% compared to their mainland Europe prices. It may be cheaper to buy non-MCS equipment and forego the RHI (for example Jaspi).

ASHP can be effective, but DECC studies show that many installations don't achieve the advertised performance efficiencies. Again, a local, competent installer who can support the system will be very important.

The problem with air to water heat pumps is that they need to be sized to heat the house on the coldest days of the year. Therefore the pump is enormous (size and cost) and runs at part load, and less efficiently most of the time.

I suspect that profits from installing big ASHPs are huge so there are some very vocal people from that industry talking up the benefits online.

I have been fascinated by an experiment by a retired power engineer, Paul Dodgshun, who has installed an air to air heat pump in his home to cover his base load space heating. It's basically an air conditioning unit running in heat mode and has a coefficient of performance of 5. So for every 1kW of electricity it uses it puts out 5 kw. He claims that running 24/7 it matches his home's heat loss (about 100 kW/day) and over the winter he will save £500 compared to using his gas CH and that's in a 4 bedroom detached house. Search for 'carbon commentary October 2013' and you'll find his postings.

On Mr D's figures, you would use only 20% of the electricity used by your night storage heaters and it would be a toss up whether you would be better off staying with economy 7.

Mr Dodgshun is very honest about his small air to air heat pump being unable to put out enough heat when the temperature is really low. He also points out that his installation cost £1600, whereas, an air to water heat pump would have been £16,000 and he will use his gas heating when his heat pump can't cope. If you don't have mains gas, he suggests buying a few portable electric heaters from B&Q at £25 each and using those on the 20 days each year when they would be needed.

It's interesting that air to air heat pumps are not included in the RHI scheme – for the obvious reason that no incentive is needed as they are already financially attractive. But as they are also comparatively cheap (£600 to buy and around the same to install) it's not surprising that nobody is promoting them when renewable heating cutomers expect to pay more.

I spent well over £2000 recently on installing a wood burning stove. I wish I had known about air to air heat pumps before I did because the capital cost would have been less and so would the cost per kilowatt hour for heat.