Gas boilers will be around for many years to come. However, at some point, the cost of running gas boilers might become much higher compared to heat pumps. Currently, well-installed heat pumps (+3.5 SCOP) might have overall advantage but for those who already have a gas boiler, it might not quite make economic sense to replace it with a heat pump just yet, especially if your gas boiler runs efficiently at over 90% on average.
Example
Using heat-engineer.com, here’s my fuel comparison. I’m currently using a gas boiler for central heating and domestic hot water (with a cylinder tank), with an Octopus Tracker dual tariff. Even with SCOP of 4, the estimated running cost is more less the same.
User Story
As a future heat pump user,
I can view and compare the cost of running gas boilers to heat pumps ,
so that I know when it makes economical sense to switch to a heat pump.
Notes for comments
What is your opinion on whether this feature would be worth adding to the heat pump monitor website?
If yes, what would be the simplest approach, since this is a heat pump monitor website and not a gas boiler monitor, so perhaps gas boiler shouldn’t be a default but an optional view?
Fuel cost comparison is tricky, since different tariffs can greatly impact the overall running costs.
Do you have any further suggestions or ideas?
OpenTherm + SAT algorithm notes. Quote:
“SAT is a Weather + Load compensator which monitors the outside and the room temperature always and carefully calculates the control Setpoint. Then, in order to apply the Low-load control algorithm. SAT monitors the boiler flow water and the return water temperatures. As a result SAT calculates the ON/OFF times in 15 minutes intervals ( SAT is also able to extend the duty cycle if the control Setpoint is too high or too low ). These two developments work tightly together in order to prevent cycling and maintain the room temperature on setpoint. Moreover we chose the 15 min duty cycle instead of 10 min that the most commercial thermostats use, this helps to reduce the ON/OFF times of the boiler by 50% during Low-load control.”
The Costs tab shows Heat p/kWh for a selection of tariffs. This is an easy way to compare against gas costs (so long as reader appreciates that gas systems are typically only 85%* efficient).
The combination of a home battery and smart tariffs can bring the running costs for ASHP down well below 3p/kWh, and the SCOP achieved by that system matters very little at that price. Add solar pv, and the cost of heating is effectively free over the year. Can’t do that with gas.
As the “spark gap” between electricity and gas reduces over time, heat pumps will become increasingly more economical.
Many heat pump owners don’t have gas at all, and so are also saving on standing charge.
There are also some non-economic benefits too, like reduced carbon emissions and increased comfort to name a couple.
Where does the 2.1 for hot water ASHP COP come from? I’d argue that is very wrong.
There are 40 systems on OEM that are monitoring hot water separately and only 2 are around 2.0, with most 3.0 and above. And lots of systems that aren’t specifically monitoring water separately but are easily getting 3.0+
I achieved 3.83 on hot water (4.2 on heating) across the 6 months of this winter (Nov to end Apr).
Better cylinders with bigger coils / plates and more attention to DHW settings is bringing much better results these days.
Thank you @Timbones. I guess this is the easiest way to quickly compare potential fuel costs.
I agree @Zarch, I tried adjusting the SCOP values to be higher but there seem to be bug in that application (SCOP doesn’t get updated after save) and I added the ground source heat pump which was slightly closer to a well-installed heat pump system.
Perhaps, what I am more interested in, is not just the Heat p/kWh but the Payback Period and Return on Investment.
Payback Period = Initial Investment / Annual Savings
i.e. Unless my gas boiler breaks down today, is it worthwhile investing in heat pump today (or with PV+Battery):
So assuming my boiler will work for the next 10 years:
What’s the average Payback Period
What’s the average overall Return of Investment, if any, if I decided to invest today (to compare savings in the 10 year period).
Example
Payback Period
Annual Savings:
Annual cost of running a gas boiler: £1,000
Annual cost of running a heat pump: £500
Annual savings by switching to a heat pump: £1,000 - £500 = £500
Initial Investment:
Cost of replacing the gas boiler with a heat pump: £4,000 (assuming grants included)
Payback Period:
Payback Period = Initial Investment / Annual Savings
Payback Period = £4,000 / £500 = 8 years
ROI (Return on Investment) Over 10 Years
ROI is calculated as the net profit from the investment divided by the cost of the investment, typically expressed as a percentage.
Total Savings Over 10 Years:
Total Savings = Annual Savings × Number of Years
Total Savings = £500 × 10 = £5,000
Net Profit:
Net Profit = Total Savings - Initial Investment
Net Profit = £5,000 - £4,000 = £1,000
ROI:
ROI = (Net Profit / Initial Investment) × 100
ROI = (£1,000 / £4,000) × 100 = 25%
Summary
Payback Period: 8 years
ROI over 10 years: 25%
Given this example, I might think… well… 8 years, maybe it’s better to wait for heat pump, battery and solar technology to improve, since my potential ROI is only 25%.
If your boiler is efficient and working well, then it makes sense to keep hold of it for now.
If you’re looking to decarbonise and reduce your impact on the climate, then ROI maybe isn’t the main factor to consider. No one considers the ROI of their foreign holiday or shiny new kitchen, just sayin…
A payback of 8 years is pretty decent, and similar to other green tech.
I would definitely get a heat pump, battery and solar today, it’s the cool technology to have! Good point @matt-drummer! Let’s hope future technology improvements balance that out for all of us.
