Fitting an ‘Air to Water’ Air Source Heat Pump (ASHP) may/may not save me anything on heating bills, I had an initial quote from Octopus Energy of £2,715.50, for one of their new ‘Cosy’ heat pumps, which includes a government grant of £7,500.00.
I have 15mm heating pipes, so no ‘microbore’ to worry about, although I might still need more and/or bigger radiators in some rooms, so the quote may increase.
Below is my conversation I had with Octopus over the viability study: (this was before I moved to the gas tracker tariff).
As an example, my gas usage for last year was 16,836kWh for hot water and heating, this was with E-ON at a lower gas price than with my current tariff at Octopus (6.78p vs 7.31p) but with a slightly higher standing charge (29.11p vs 27.47p per day).
This means that assuming no change in usage, just by switching to the Octopus tariff, my gas costs will go up from £1,247.73 to £1,330.98 (a loss of £83.24)
The worked example makes use of a CoP of 3, so assuming 82.5% efficiency of my gas boiler and applying the 3:1 CoP to the 16,836kWh gives me 4,629kWh of electricity needed to run the Heat Pump, which at an average cost of 27p/kWh gives a cost of £1,250.07 (a saving of £80.90 a year, also assuming no gas standing charge) which means a return on investment of around 33 years.
Assuming a CoP of 3.5, this improves slightly to a saving of around £250.00 per year and just over 10 years RoI, this may also improve further depending on the tariff being used. My current Intelligent Octopus Go tariff is potentially a lot better than the Cosy Octopus tariff in just about every regard, despite only having one ‘dip’, both my peak and low rates are 10p/kWh cheaper.
Unless there is a substantial increase in the price of gas, substantial drop in electricity prices or the CoP on the heat pump is guaranteed to be above 4, I am not really seeing this as a viable option, when I can potentially make similar savings with my £350.00 Eddi unit (1 hour to fit and install) and diverting excess solar on sunny days for a much faster RoI.
I admit that I could also divert excess solar to the heat pump, however there is still the initial outlay and upheaval associated with the install and the worry about ongoing support (a current lack of engineers being available to support/fix faults), although it appears they have their own set of service engineers, so maybe less of a concern here.
I would also retain the ability to boost heat/hot water as required due to the instant nature of the gas boiler.
With my recent move to the gas tracker tariff, this makes even less sense with my gas cost for the same 16,836kWh now being around £673.44.
My boiler is actually around 90% efficient, so a CoP of 3:1 would mean 5,050kWh of electricity or 4,329kWh at a CoP of 3.5:1, even at my new average with solar and batteries of £0.22/kWh, the 3.5 CoP cost comes out to £952.43 for the year or £278.99 more expensive for the year than running on gas.
If I had an Oil, older gas or an electric boiler then I think I would be more willing to make the jump, however at present, even with the Government grant, I can’t see this making economic sense for me.
An ‘Air to Air’ ASHP may make more sense, these typically have a CoP of 4 (3788kWh from avove calculations) or above, however there is no grant available for these at present and, would require some major thinking with regards where to install both the heat pumps and the blowers and I would still need to find a way to heat my hot water, although this could potentially be via the Eddi and still no guarantee I would actually see any ROI. The ASHP at 4:1 CoP would cost me £833.38 for the year, which is still 159.94 per year more than my current gas based system.
Even factoring in the £98.89 standing charge for the year, I still can’t even come close to breaking even on the annual costs of any ASHP system, let alone see an ROI.