Changing boilers

Reed_Richards

Grant actually make a hybrid system that combines an oil boiler and an ASHP side-by-side in a single unit.  I didn't like this idea because I would have needed  a new oil tank to continue with any use of oil but perhaps it allows you to run at higher water temperatures and so keep your existing radiators?

lohr500

I think the problem with the hybrid systems is that they don't qualify for the RHI grant. I could be wrong on this. So it would be a very expensive install.

Reed_Richards

With a hybrid system you have to install metering to work out how much of the heat comes from the heat pump and your RHI is based on that (I think).

lohr500

Thanks for correcting me Reed_Richards. Hybrid systems do qualify but as you say you need metering to determine the RHI payment amount. 
https://www.ofgem.gov.uk/system/files/docs/2018/07/essentialguidetometering_july_2018.pdf

matelodave

I really cannot see any advantage in having a hybrid system apart from the fact it might be a bit greener and you can probably get most of your hot water and heating from the heatpump, supplementing it with the boiler if and when the heatpump cant cope. I guess that the hp would be spec'd with the xpectation that there would be  a certain amount of time that the oil boiler woud be expected to run. 

You have the additional cost of installing and maintaining two heating sources, yo've still got tto find space for the oil tank as well as the external unit for the heat pump. As said above you've got the extra cost and hassle of metering (you have to submit regular heat meter readings to get RHI and you only get paid for what the heatpump produces). You've probably gor a bit of extra complexity with the controls as well to minimise use of the oil boiler in favour of the heatpump.

The cost of heating with either oil or the heatpump are pretty well on a par, probably with oil still being a bit cheaper than leccy depending how well you can optimise the heatpump and how cheap you can get your leccy.

They both require electricity to run them so you can't really use the arguement that one is a back-up for the other.

Reed_Richards

The main benefit of the hybrid arises when you can't get a heat pump with enough capacity on its own, I imagine.  Personally I agree that a hybrid is best avoided if you can manage to do so.