Switching from oil to a heat pump

[Avocet]

Are BOTH numbers just Guesstimates?
i.e. best guesses based on the limited info they both have on your home's heating and water needs - possibly from somewhere such as the last EPC, perhaps? Such that BOTH are subject to a (paid for) survey and room by room heat loss/gain calculations to refine what is actually needed (and the cost no doubt)?

Do both include the cost of removal and licensed disposal of oil boiler, tank, pipework including any kerosene left in the tank?

The 150 litre water cylinder is a tad small for a family home, and the 300 litre a tad large... So the two 'quotes' seem not to be "like for like" assumptions at all.

Octopus only seem to offer their own Cosy Heat Pumps up to 11.3kW heat loss and the Grant 15.5kW for larger, lossier homes... Not sure I'd be keen on their own brand (must do more reading on them in those other forums).

The Heatgeeks one will be a guesstimate. I just went on their website, stuck in my address and a couple of details and left its algorithm to "do its thing". The Octopus one was after a bloke came and spent about three hours here, measuring windows and the like.

The Heatgeeks one came with an estimated 12.66kW heat loss (don't know how, but we do have a pretty recent EPC. They estimated the floor area at 208m^2 the Octopus one reckoned 193m^2 (I know, because I have accurate drawings from when we extended the house in 2008 that it's actually 219m^2, but the Octopus guy said he'd knock the porch off as we don't heat that). Either way, they're in the same ball park. Octopus reckoned the heat loss was 10.578 kW

Slightly puzzling that Heatgeeks are recommending a smaller pump for a higher heat loss and floor area though? The Octopus quote assumes a design outdoor temperature of -3.7 decrees C. Heatgeeks guarantees an efficiency of 340%. With Octopus it's 360%, but in the smallprint it says that's an annual average, whereas the Heatgeeks quote doesn't say what it's based on, but I'm assuming that 340% at even zero degrees outside, is "optimistic"?

Apologies, the Heatgeeks quote was for a 210L cylinder not 150.

NEITHER includes anything to do with getting rid of the existing oil tank or its contents - although the latter won't be a problem round here, as lots of people are still on oil and I reckon I can sell that at £20 for a 25l drum! Plenty of farmers always looking for oil oil tanks too.

 

[drives]

The heatgeek efficiency guarantee will be the SCOP (annual) as well.

Only one way the heatgeek quote will be going presumably once they do a survey, and they may well be sizing up the unit afterwards.

That octopus quote will be very difficult to beat I think. The proposed unit sizing looks reasonable, taking into account the calculated heat loss (which again on the face of it sounds about right for the size of your house and if average insulation levels for year), and giving a bit of a buffer for DHW demand and defrost cycles.

 

[Razor900]

What was the design flow temperature for the Octopus setup?

 

[Avocet]

What was the design flow temperature for the Octopus setup?

50 degrees C

 

[ericmark]

Be it oil, gas, or heat pump, correct size is important. Too small that's obvious, but also too big reduces efficiency.

But the amount too big reduces efficiency is far more marked with a heat pump.

So my house, all windows renewed, loft insulation fitted, result, the oil boiler is now too big, likely always too big, but 14 heated areas, and if the central heating fails, the 800 watt oil filled radiator will maintain any room's temperature. So simple maths 0.8 x 14 = 11.2 kW, so why have I got a 20 kW oil boiler?

The theory is the shorter the reheat time, then the lower the back-ground temperature for any room. And this leads on to also the lower the losses are. The problem is for that to work, the radiators need to be bigger, if I am only using 3 rooms at a time, the three rooms in use need to sink 20 kW with their radiators, and the radiators can only sink around 6 kW between them if the TRV heads are wide open.

So the boiler is cycling on/off all the time. OK for my non modulating oil boiler, but once you're using a modulating boiler, it is the minium output which is important, or they are not running efficiently.

So we have some expert fit a heat pump, and for the first time in decades we have a heating device small enough and radiators large enough for it to run efficiently. Nothing to do with being a heat pump, it's all to do with getting the size right.

I look back at my mother house, a lot smaller than mine, but with a 35 kW gas boiler, reason given was to be big enough to fill the bath in a reasonable time, one, the bath was rarely used, and two, could have used a storage tank, and a lot smaller boiler. So we look at the heat pump, and guess what, we have a hot water storage tank again.

If I want to save money on heating, likely a small oil heater just heating the living room would be the answer, I can get a gas one, either type would fit in my house nicely, and reduce likely by half the days when I want the central heating running, but not really seen an oil fired one I like, and also there is no vent to feed the combustion air into the fire, so they cause a draft.

 

[Razor900]

50 degrees C

Thats reasonable