Saving on heating bills

[peter]

I didn’t say that we didn’t reduce the humidity - which we did by opening the windows regularly - only that we never achieved low humidity.

How low is low - what target humidity did you program into the dehumidifier? Since it was never reached, presumably it ran constantly.

Were you able to objectively compare the results of the two methods, for example did you take regular readings with a hygrometer? Or is it more a case of neither approach did what you wanted, but based on your experience your preference is for the window method?

 

[Pauline]

Peter, we were living our lives, not conducting a scientific experiment. I did say right at the start of this discussion that I was talking about my own experience - other people's experiences may well be different.

Very few of the choices we make in our daily lives are based on life or death scenarios, and science doesn't always give us definitive answers as it can't always take account of individual circumstances or individual perceptions of quality of life. So, many of our choices are based largely on personal experience and preferences, and inevitably that means different people will reach different conclusions. That doesn't make one person right and another wrong, nor should we have to justify our choices to anyone but ourselves.

If I had to choose between what I consider the largely intolerable noise of a dehumidifier along with never opening the windows for fresh air, versus an additional £2* a week (say) on heating costs, the latter would win hands down every time. Maybe I am lucky in being able to choose quality of life over worrying about every last penny.

* I have plucked this figure out of the air, and considering our total heating costs last winter, it is probably pessimistically high; it also doesn't take into account the costs that would be involved in purchasing and running a dehumidifier.

 

[peter]

Pauline, thanks for the clarification. You're right, you don't have to justify your personal preferences, but it's helpful to know what the basis is for comments as this might affect other people's decisions.

Hopefully none of us has to worry over every last penny, but the saying 'look after the pennies and the pounds will look after themselves' has, inflation and decimalisation notwithstanding, still got the ring of truth. We all weigh up the pros and cons and reach what is (hopefully) the right decision for us, and the more reliable information we have the more likely we are to be right.

As I get older I am better able to chart my financial course through to the inevitable end point, and this makes it easier to decide whether I can justify spending a bit more on something. I now prioritise convenience and timesaving more than I did when I was younger, so if I lived somewhere which was damp because of poor construction I'd either rectify the problem once and for all, or use a dehumidifier. Opening windows for long periods and experiencing draughts of cold air appealed to me when I was younger - for the first 50 years of my life I couldn't sleep unless my bedroom window was open - but now it neither appeals nor makes financial sense.

 

[Pauline]

Thinking more towards future savings on heating (financial and environmental), I see the UK government are now offering £5000 grants towards the purchase of heat pumps. I'm wondering how realistic it is for many people in the UK to switch from boilers to heat pumps, either ground source or air source, as my understanding is that the cost of the pump itself can pale into insignificance compared with installation costs. It will of course depend on things like how good the existing insulation is, and how much the internal plumbing has to be altered.

For many homes, ground source heat pumps will not be an option, and some homes will not be big enough to install either.

 

[peter]

my understanding is that the cost of the pump itself can pale into insignificance compared with installation costs. It will of course depend on things like how good the existing insulation is, and how much the internal plumbing has to be altered

I looked into it some years ago and found out that heat pumps work best with underfloor heating. The efficiency of the heat pump is greatest when the increase in temperature is smallest, which would require very large radiators. Another advantage of solid floors and underfloor heating is that if you have a ground source heat pump you can run it at night on cheap rate electricity.

We ended up replacing our very old oil boiler with a new and much more efficient oil boiler, but we also reduced heat loss with thicker roof insulation and perspex secondary glazing, both of which are very cost-effective. But even sticking with the same type of heat source the cost of the boiler was only a small part of the total cost.

 

[Pauline]

Since it’s reckoned that most domestic heat pumps will need to be air source, which are less efficient, and since it’s likely that heating water to a reasonable temperature will require an additional heat source, which for most people will mean an electric immersion heater, I wonder why electric boilers are not being considered more as a viable option. These can also run a combi system, so installation would be simpler and cheaper, and there are no emissions at the point of use. These would become greener if the electricity used to run them was from renewable sources.

 

[peter]

Since it’s reckoned that most domestic heat pumps will need to be air source, which are less efficient, and since it’s likely that heating water to a reasonable temperature will require an additional heat source, which for most people will mean an electric immersion heater, I wonder why electric boilers are not being considered more as a viable option. These can also run a combi system, so installation would be simpler and cheaper, and there are no emissions at the point of use. These would become greener if the electricity used to run them was from renewable sources.

Electric boilers are much less efficient than heat pumps, which can produce 4kw of output for 1kw of input in ideal conditions (3kw is more typical). A conventional electric heater can only ever produce 1kw output for 1kw input. It's only because of the better efficiency of heat pumps that they can compete with gas on running costs (gas is normally much cheaper than electricity).

Water doesn't need to be very hot for bathing - the hottest temperature most people can bear is 44C. Heat pumps can heat water to higher temperatures, they're just not as efficient when used that way, so it doesn't make sense to design a central heating system that requires really hot water. Conventional heating systems use water at a minimum of 60C but it can be higher.

 

[Pauline]

Electric boilers are much less efficient than heat pumps

Yes, and as you say, nothing can ever change that. But thinking practically, I was wondering if electric boilers may be a more feasible and affordable alternative to gas boilers than heat pumps - no more energy efficient, but a big improvement as far as emissions go.

Insufficiently hot water for baths and showers etc is often cited as one way in which heat pumps can fall short. Warm rather than hot bathing in winter can leave people feeling chilled and wanting more room heat to warm up again, so it has sometimes been said to be a false economy, but it’s also very much down to personal preference. And, if the water temperature is lower, you need a larger hot water cylinder, which means yet more space.

I think this is one of those very difficult issues - clearly the way we heat our homes needs to change, but to make it happen we also need to find greener ways that are both practical and affordable for the average householder.

 

[peter]

Yes, and as you say, nothing can ever change that. But thinking practically, I was wondering if electric boilers may be a more feasible and affordable alternative to gas boilers than heat pumps - no more energy efficient, but a big improvement as far as emissions go.

People aren't going to be prepared to pay three times as much for their heating, so electric boilers aren't a realistic alternative to gas. And they're not necessarily greener - the electricity has to be generated somehow.

Insufficiently hot water for baths and showers etc is often cited as one way in which heat pumps can fall short. Warm rather than hot bathing in winter can leave people feeling chilled and wanting more room heat to warm up again, so it has sometimes been said to be a false economy, but it’s also very much down to personal preference. And, if the water temperature is lower, you need a larger hot water cylinder, which means yet more space.

As I noted earlier, heat pumps are perfectly capable of producing hotter water, they're just not as efficient when there is a large temperature differential. However they're ALWAYS going to be more efficient than an electric boiler or immersion heater.

 

[Bryman]

the UK government are now offering £5000 grants towards the purchase of heat pumps

That seems very generous. Without going into a lot of detail, I believe that would be the likely cost of 2-3 air-sourced units (including installation) here in NZ.

most domestic heat pumps will need to be air source, which are less efficient

That would be true in urban areas as ground-sourced systems would require more land than is generally available. Although ground-sourced systems can be more efficient, the initial installation cost is much greater. Another point to consider is the winter environment of the location where the system is to be run. Although we have enough land to accommodate a ground-sourced system, we installed an air-sourced unit as our environment is similar to the South of England, often without snow in winter. Air-sourced units would not be appropriate in more extreme environments as they would be much more expensive to run with colder air.

my understanding is that the cost of the pump itself can pale into insignificance compared with installation costs

That may be true for ground-sourced systems but should not be so for air-sourced systems supplying warm/hot air via wall-hung units inside the home.

These would become greener if the electricity used to run them was from renewable sources.

True but impossible to use electricity only from renewable sources when connected to the national grid supplied from various sources. I am billed by a company which only generates from "wind/water/sun" but I may be using electricity generated from "coal/oil/gas" if that is inserted into the grid.

 

[Bryman]

Another advantage of solid floors and underfloor heating is that if you have a ground source heat pump you can run it at night on cheap rate electricity.

My underfloor heating works fine using an air-sourced unit pumping water at about 30C through several separate pipes in the floor slab. It is difficult to add such underfloor heating to an existing house and is really only practical for a new build.

 

[Bryman]

Water doesn't need to be very hot for bathing - the hottest temperature most people can bear is 44C. Heat pumps can heat water to higher temperatures, they're just not as efficient when used that way, so it doesn't make sense to design a central heating system that requires really hot water. Conventional heating systems use water at a minimum of 60C but it can be higher.

Agreed. My conventional boiler system in UK circulated water through wall-hung radiators at about 80C. The heat pump here in NZ rarely heats water for bathing above about 50C but the hot tank is about double the size of the one we had in UK and better insulated.

 

[At home in NZ]

The heat pump here in NZ rarely heats water for bathing above about 50C but the hot tank is about double the size of the one we had in UK and better insulated.

I wasn't aware of a heat pump that will heat water being available in NZ We have two heat pumps, one at each end of the house, they hang on the wall just below ceiling height and heat or cool the air in the room depending on how they are set.
One was already installed when we bought the house, we had the second one installed about 3 maybe 4 years ago which cost around $2,000 including installation. The model we have hasn't increased very much in price.

 

[peter]

I wasn't aware of a heat pump that will heat water being available in NZ We have two heat pumps, one at each end of the house, they hang on the wall just below ceiling height and heat or cool the air in the room depending on how they are set.
One was already installed when we bought the house, we had the second one installed about 3 maybe 4 years ago which cost around $2,000 including installation. The model we have hasn't increased very much in price.

Those are obviously smaller in scale than the heat pumps that are proposed for the UK. What you're describing sounds like the sort of air-conditioning system common in Portugal, which heat air in the winter and cool it in the summer - like the air-conditioning system in my electric car. We can buy similar systems in the UK at similar prices, but systems capable of cooling won't qualify for the grant.

 

[At home in NZ]

Those are obviously smaller in scale than the heat pumps that are proposed for the UK. What you're describing sounds like the sort of air-conditioning system common in Portugal, which heat air in the winter and cool it in the summer - like the air-conditioning system in my electric car. We can buy similar systems in the UK at similar prices, but systems capable of cooling won't qualify for the grant.

I probably haven't read the whole discussion properly because I don't know what grant you are referring to. Having Googled heat pumps NZ I find there is a grant/subsidy available, as usual I wouldn't qualify! However, the subsidy is 80% of the cost of an approved heater which can be a heat pump or efficient wood burner.
This is what the heat pump looks like, they operate by remote control:


They are in common use here in this part of NZ.

 

[Pauline]

That seems very generous. Without going into a lot of detail, I believe that would be the likely cost of 2-3 air-sourced units (including installation) here in NZ

Figures quoted yesterday for heat pumps in the UK are £6000 to £18000, depending on size and type, and this doesn't seem to include installation costs.

When I was talking about installation costs, I was including the various associated costs, such as upgrading insulation, optionally installing under-floor heating and/or increasing radiator size, and for homes currently on a combi system (which many now are), installing a hot water cylinder (and a cold water tank in the loft?) and re-routing existing plumbing. This last one is an essential for heating hot water with a heat pump, and depending on how much kitchens and bathrooms etc need to be de-constructed and re-constructed while re-routing the plumbing, can be pretty expensive.

Most things I've read suggest that in general supplementary water heating will be needed in the UK, particularly with air source heat pumps, though this may not be the case if people have - or have room to install - a larger than standard hot water cylinder.

Also, just to clarify, my comments about electric boilers were not intended to suggest that I think they are a good alternative to heat pumps, but whether they might provide a good option where a heat pump is not financially or logistically viable. The government is currently talking about replacing gas boilers with hydrogen boilers when a heat pump is not viable, but this isn't yet possible, and there seems to be some debate about whether it ever will be.

 

[peter]

This is what the heat pump looks like,

That's what we'd call an air-conditioning unit in Europe. The heat pump is usually a separate unit fitted to an external wall or on the roof and connected to the in-room unit by pipes. One heat pump can often feed 2 or 3 in-room units.

You can see an example here.

Also, just to clarify, my comments about electric boilers were not intended to suggest that I think they are a good alternative to heat pumps, but whether they might provide a good option where a heat pump is not financially or logistically viable.

It's a good practical option, but unworkable financially - nobody is going to change from a gas boiler if it means their annual bills will be 3 times higher.

Electric storage heaters were designed to overcome this problem (of electricity being so much more expensive than gas) by using cheap Economy 7 electricity, but off-peak electricity is no longer as cheap as it was. Heat pumps are the successors to electric storage heaters (literally when combined with solid floors with underfloor heating).

The cheapest way to heat a house would be a gas-fuelled heat pump - you can still buy gas-powered refrigerators if you look hard enough. But since the objective is to move away from fossil fuels it wouldn't be a good choice.

 

[Margery]

That's what we'd call an air-conditioning unit in Europe

And in Australia.

 

[Pauline]

nobody is going to change from a gas boiler if it means their annual bills will be 3 times higher.

Well, I was thinking more of when gas boilers are being phased out rather than now. But there is talk of moving green levies from electricity to gas, and with the current rise in gas prices (and more expected) will electricity always be the more expensive option? Maintenance costs are also much lower for electric boilers.

But mostly I'm just thinking out loud here!

 

[peter]

You can see the price differential between gas and electricity wholesale prices here

Note that the gas price is shown in pence per therm, the electricity price in pounds per megawatt hour. To convert the former to the latter divide by 2.93, thus tomorrow's gas price of 209p per therm translates to £71.33 per megawatt hour, compared to the electricity price of £159.50

This is a smaller differential than usual because of the current gas shortage. If you look at the prices a year ahead, gas is 124.54p per therm, equivalent to £42.51 per MWh, electricity is £116.19, so almost 3 times as expensive.