Air pump, electric boiler or both! 23 February at 12:58PM in LPG, heating oil, solid & other fuels 17 replies 292 views

CF2022

We live in a 2 bed 1850 end terrace house with a current EPC rating of E. We have just had solar panels fitted and are looking to update our current oil heating system. 

Gas is not an option and we have been quoted £7500 to change our oil boiler to a combi, remove the water tank and move our oil tank outside (it is currently in the garage and deemed very unsafe). Weve also been quoted double for this! 

We have no issue with our system currently, except we want the space from the 2 tanks and we're not happy with where we could put it outside. For the prices we've been quoted we decided we may as well look at other options altogether.

This has been a complete mine field! Weve looked at heat source air pumps, which we're not sure with our current epc rating we would get the government grant. We've had fischer round who quoted a hybrid system of an electric boiler for heating and an air source water heating system. Reading on here though I don't feel comfortable going with anything Fischer related. Our next step is Octopus Energy are going to quote for a heat pump.

We're really not sure on the best way to go. Any advice, questions we should be asking, real world experience in a similar size house would be greatly appreciated.

thrope

I would suggest to get some more quotes from local oil boiler fitters to get a second opinion on if the tank needs to be moved, whether a combi is the best option if you have a working hot water tank. It's likely the radiators would need to be a larger size for a heat pump. New oil boilers can easily change to work on HVO so they can be decarbonised in the future.

Reed_Richards

I switched from an oil boiler to an Air Source Heat Pump.  To do this I also had to replace almost all my radiators with ones with a larger surface area (although not necessarily occupying any more wall space).  Although I don't regret making the change, at current fuel prices an oil boiler is cheaper to run than a gas boiler or an ASHP.  An electric boiler would cost an arm and a leg to run (about 3 times as much as gas or an ASHP).   

Ectophile

I suspect if you install an electric boiler, your EPC may go down even further.  The only thing more expensive for heating is burnung £20 notes in your fireplace.

Apodemus

...and unless I am much mistaken, an ASHP will not remove your need for a hotwater cylinder - only a combi is going to do that.

Reed_Richards

That's correct.  I think the days of combi boilers may be numbered.

Apodemus

Reed_Richards said:

That's correct.  I think the days of combi boilers may be numbered.

Yes, but there will be so many people who have converted the space where their hot water tank used to be and will struggle to reinstate it when they need to change back.

CF2022

Reed_Richards said:

I switched from an oil boiler to an Air Source Heat Pump.  To do this I also had to replace almost all my radiators with ones with a larger surface area (although not necessarily occupying any more wall space).  Although I don't regret making the change, at current fuel prices an oil boiler is cheaper to run than a gas boiler or an ASHP.  An electric boiler would cost an arm and a leg to run (about 3 times as much as gas or an ASHP).   

Hmm no one has mentioned changing radiators to us. Would the efficiency and solar offset the higher unit cost of electric?

BUFF

At current energy unit prices an ASHP with a COP ~3 & a condensing gas boiler cost similar to run,  a condensing oil boiler will be cheaper (but who knows about the relative cost of fuel down the line).
The potential issue with solar is that it produces least when you need it most (winter) - you will most likely need to draw from the grid to power an ASHP 24/7.

Reed_Richards

CF2022 said:

Hmm no one has mentioned changing radiators to us. 

That's probably because you have not yet seen anyone who is serious about installing an ASHP.  I'm sure Octopus Energy, when they quote, will mention this.

tacpot12

Your 1850's terrace house has a lot of thermal mass. Also, if you are mid-terrace, you have two other heatings systems on either side keeping your house warm, so you will not have to run an ASHP 24x7 in the winter. You should be able to have it off between say 9pm and 3am. In this time, the temperature in the house will fall, but not buy much, and the period beween 3am and when you get up should warm the house back up again. 

You won't get a lot of solar gain during the winter days, due to small windows, but you will get a cost saving running the ASHP from the solar panels and due to the warmer outdoor temperature (as more heat is available to collect from the environment).

You need to have the radiators AND radiator pipe sizes checked if you go down the ASHP route. Most people don't need changes because of how the rules of thumb used by plumbers in the 1970s, 80s and 90s tended to oversize radiators, and because microbore pipes were not used that commonly, but you need these to be checked if you are to avoid a big shock with the running costs.

The risk of the installation not being efficient is one that the ASHP industry hasn't solved yet. A good installer will be able to install an ASHP and be able to (more or less) guarantee the performance.

Other things to consider are:

• have you got enough insulation in the loft (270-300mm is ideal) 
• have you got good double-glazing 
• have you eliminated all the draughts

Really, the size of the ASHP indoor unit (assuming it includes a water tank) is the biggest problem you have to solve. If you can't fit the ASHP indoor unit into the garage, then an oil combi-boiler would be the best solution.