KW usage heat pump quote

todayisagreatday

OK, so I've been getting quotes for a water souce heat pump with the Nuenta energy blades mentioned in a previous thread based on our plans and curremt EPC.



One thing I'm confused about in the huge amount of emails is this statement below:



Total estimated annual heating & hot water consumption: 21,989kWh



Eligible Usage (energy taken from sustainable sources): 21,989kWh x (1 - 1/4.73) = 17,340kWh



Total annual RHI payments = 17,340kWh x 20.46p/kWh = £3,548 a year for 7 years



Ignoring the RHI payments our estimated heating and hot water consumption is over 20,000 units..... So generally comparing electricity prices if I was getting an idea of how much we'd be paying on 21000 units a year works out around £3k based on currently electric prices. 

Is this right? I mean it's a two bed bungalow at the moment 100m2 and will be just over double and we only use £20 a month electric (electric showers, sometimes immersion but heating is oil).... It seems a huge jump

lovesgshp

It is too vague what you are asking.
What is the size of the pump, is it underfloor or radiator heating? Will it have a separate hot water tank? What temperature do you want to keep the house at for normal use? What level is the insulation going to be?

Cardew

So generally comparing electricity prices if I was getting an idea of how much we'd be paying on 21000 units a year works out around £3k based on currently electric prices. 

You wouldn't 'be paying on 21,000 units a year' I think you are not taking into account the COP of the heat pump. If you need 21,000kWh(units) pa for heating and hot water; with a GSHP you could expect to have an average COP of, say, 3.0. Therefore you would use 7,000kWh pa.

matelodave

What does your EPC say - the RHI is calculated on what the EPC calculates your energy requirement.

My 140sq.m 1986 detached three bedroomed bungalow which has cavity wall insulation, double glazing and 300mm loft insulation has a D rating.

The EPC calculates an annual space heating requirement of 12565kwh and an annual water heating requirement of 2759kwh. Giving a total heat requirement of 15324kwh/pa.

I have an 11kw Air to water heat pump which supplies all our hot water and underfloor heating all over.

My SPF is deemed to be 2.5 which means I get RHI on 0.6 x 15324
= 9196kwh at only 8p/kwh because it's an air-water heatpump = £735 per annum for seven years = around 5k in total which is about what the unit cost in 2010.

In reality my average total annual electricity consumption (over the past eight years) is only around 7200kwh of which I estimate about 4500kwh is for heating and hot water via my heatpump.

My unit has been in service for just over eight years and I've so far had about four years worth of RHI.

If you are adding another 100sq.m then it would have to be built to a better spec than the existing building and I'd guess that the calculations wil be a lot more complex but 22000kwh does sound a bit over the top. You'd need to have an up to date EPC to be able to properly calculate your RHI.

todayisagreatday

Cardew wrote: »

You wouldn't 'be paying on 21,000 units a year' I think you are not taking into account the COP of the heat pump. If you need 21,000kWh(units) pa for heating and hot water; with a GSHP you could expect to have an average COP of, say, 3.0. Therefore you would use 7,000kWh pa.

That is exactly what I'd done! I hadn't taken into account the CoP which I'd realised late last night.... The rest I'm currently working through but the penny finally dropped...