Heat pump install to existing UFH system?

seraphina

Hi, a bit of a newbie and would appreciate a bit of guidance.

We have a modern (built 2005) 5 bed detached house, that has wet UFH throughout downstairs and 6 radiators and 3 towel rails upstairs. Big pressurised hot water tank, and we are on oil fired central heating, with very occasional immersion boosts if we are going through a lot of hot water. Moderate amount of loft insulation, and double glazing throughout. Currently about £4000 year on heating and hot water, but we aren’t particularly frugal.

Does having wet UFH throughout downstairs mean that installation of a heat pump would be more straightforward?

matelodave

I guess it depends on how your existing system is configured, Some systems with underfloor heating downstairs and upstairs rads/towel rails have separate zones with an extra pump and mixer valve to run the underfloor heating at a lower temperature than the rads. Rads tend to have flow temps of around 59-60 degrees or more whereas u/f heating us usually nearer 35-45

You really need to get a proper survey and do some calculations to see if there are any changes to be made to balance the system to suit lower flow temps from a heatpump. I doubt that having a mixture or u/f and rads will make it either harder or easier to incorporate a heatpump rather than oil, just different. 

Like all systems it needs to be specified correctly, just swapping an oil boiler for a heatpump is unlikely to work satisfactorily or economically unless the rest of the system is tweaked to match.

As you've also probably gleaned from the many threads on heatpumps,  having proper controls and using them correctly are also very important to get a system operating the way you want it to without it costing a fortune to run.

£4k on oil sounds like an awful lot of money for heating and hot water and unless you get a heatpump configured and operated correctly it could cost you even more in electricity. I dont know what oil costs per litre but as you get 10kwh a litre you need to do your sums to work out roughly how many kwh a year you use. 

Divide that number by 3 to get an estimate of the amount of electricity a heatoump would use to generate the same number of kwh and then multiply that by the price of leccy to give yourself a very rough idea of how much it would cost to run a heatpump.

Personally, I'd put quite a bit of effort into tweaking my present system to try and see how well you could minimise your costs to help you understand how to use it better before embarking on a heatpump.

Reed_Richards

seraphina said:

Does having wet UFH throughout downstairs mean that installation of a heat pump would be more straightforward?

No.  In my opinion a mixture of UFH and radiators makes for a more complex situation that just on or just the other throughout.  However it can still be done and frequently is.

I agree that £4k per year for heating and hot water is quite a lot.  Perhaps you should consider more loft insulation?    

Rodders53

This is an all depends question. 
Kerosene here is, today, being quoted at around 57p/litre (1000l rate) has been lower (and higher).  So circa 6p per kWh.

The most I paid was 83p/l and the least 31p/litre (but others have had cheaper and more expensive prices).  So £s are useless for energy comparison purposes... I have spent £5,220 on kerosene in 8 years here or just over 10,000 litres (38 litres over, to be precise).

With a kerosene boiler it should never be necessary to boost HW with an immersion element --- my HW cylinder has a reheat time of around 30 minutes via the coil (electric immersion taking hours to do the same).

With a COP of 4 (probably not quite unachievable even with the latest HPs?) 25.2 p / kWh input (current price cap) or 6.3 p / kWh heat output.  A heat pump won't save you any money in all probability.   Especially if you need a lot of hot, hot water - that'll need full rate immersion to supply it or an exceedingly poor COP with the HP to get to 60C+.

I'm in a similar age detached 4/5 bed with (in my view poorly installed) UFH and 8 radiators (2 towel rails replaced with rads for warmth in the bathrooms),  Our kerosene use is under £1000 per annum but there is only two of us.  We do have Air to Air heat pumps which we use around this time of year for a heat boost in lounge and kitchen diner rather than run the UFH. 

An Air to Water Heat Pump will make the UFH easier to run at very low temperature for longer and remove the issues around kerosene boiler cycling to maintain the (low) water temperature and to incorporate better controls, weather compensation and so on.

FreeBear

Rodders53 said: With a COP of 4 (probably not quite unachievable even with the latest HPs?) 25.2 p / kWh input (current price cap) or 6.3 p / kWh heat output.  A heat pump won't save you any money in all probability.   Especially if you need a lot of hot, hot water - that'll need full rate immersion to supply it or an exceedingly poor COP with the HP to get to 60C+.

But if you have a heat pump, it makes sense to move to a dedicated tariff (say Octopus Cosy) where you have cheaper slots at 12.65p/kWh (Eastern region). Potentially cutting the cost of heat to ~3.2p/kWh. However, with a high demand for DHW, I'd agree that a HP might not be a cheaper alternative - Perhaps a hybrid system with a HP for heating, and a boiler for the DHW backed up with lots of insulation.

seraphina

Oh this is super helpful, thank you. I should clarify, the £4k is our total electric and oil bill for the whole year, so not just heating/hot water. We are reasonably intensive users of hot water.

We would very much like to go down the heat pump route, but we are struggling to make the numbers work. Oil is generally coming down in price, and the repayment time on the £7.5k that we estimate the installation will cost is not insignificant. Also a very similar house in our street has solar panels and ASHP, and they have to supplement their downstairs with oil filled radiators. A hybrid system seems like the worst of both worlds - the expense of maintaining an oil boiler in addition to the costs of an ASHP install.

And yes to insulating the loft more, it would be our first priority.

Reed_Richards

I think the only reason for considering a hybrid system should be that your house demands so much heating that a heat pump alone could not manage.  That's an unfortunate situation to be in because it means you will have large annual heating bills, whichever heat source you choose.  An oil boiler and a heat pump should have similar running costs based on current prices for heating oils and (SVT) electricity.  Your near-neighbours must have something wrong with their system if they need supplementary downstairs heating.  

You can get a grant of £7.5k towards your heat pump installation and Octopus are offering some very competitive quotes, although they don't cover every area.

.  

FreeBear

seraphina said: We would very much like to go down the heat pump route, but we are struggling to make the numbers work. Oil is generally coming down in price, and the repayment time on the £7.5k that we estimate the installation will cost is not insignificant. Also a very similar house in our street has solar panels and ASHP, and they have to supplement their downstairs with oil filled radiators. A hybrid system seems like the worst of both worlds - the expense of maintaining an oil boiler in addition to the costs of an ASHP install.

If you went for a hybrid system, you'd loose the £7500 BUS grant, so that needs to be factored in to any costings.