I run daily comparisons between a gas boiler and a heat pump in the UK. Given that gas is cheaper than electricity, a well-installed and well-controlled gas boiler can still be cheaper to run. Heat pump running costs can drop drastically when combined with solar and battery storage, but that requires a much greater upfront investment.
I'm no expert on UK energy pricing, but the main difference between a boiler and heat pump is that heatpump can be, eg "500% efficient" - a COP of 5. So even if a KWH of energy is 2x the price for electricity a heatpump often comes out ahead.
Electricity in the UK is often 3x or more expensive than electricity for the same energy content. We have some of the most expensive electricity in the world.
Yeah a COP of 5 is very good. 3 is much more typical.
And OP is right. When I've looked into it you aren't going to save any money going to a heat pump; in fact it will likely increase costs slightly.
So it really only makes sense to do when you need a new boiler. If you don't, it makes way more sense to get solar because that's also good for the environment but actually saves you money.
COP of 5 when running in perfect conditions (load, EWT temps, variable stage compressor, infinite heat sink/source). You might want to research how realistic constant COP of 5 really is.
I've ended up with a "hybrid" system, which (claims to) automatically choose which of gas and electricity is cheaper on a minute by minute based on COP derived from temperature. I have solar panels but not a battery. On net, it's ended up as roughly the same price as the old gas boiler. Better CO2 emissions but not that much cheaper.
It's not automatically linked to rate updates. There's probably a way of automating that for Vaillant systems?
(Shoutout to ProllyInfamous, who's been making the great point that in many climates HW systems that also cool and dehumidify are a great benefit. Not here at 56N, though)
Seems like a decent place to point out that there are good savings to be had on heat pump running costs with a smart controller designed for heat pumps which can learn the dynamics of your building then preheat when tariffs are low or outdoor conditions are favourable.
I work for homely energy which has such an offering, but fwiw I genuinely think it's a good product. It's been studied by Salford uni in their energy house lab, so if anyone's interested maybe dig into that for a more neutral verdict.
On one of your graphs you have the CO2 per day of gas and heat pumps but the two use different scales on the same graph.
Another graph in a footnote table shows the heat pump is delivering 6x the heat of the gas boiler, which feels like it should be mentioned in the text when you say it costs 3x more.
And actually that makes the previously mentioned CO2 graph even more misleading.
I have always wondered if a heat pump is even worth it if you don't have solar, all well and good the government giving massive discounts on heatpumps but not for a combined heatpump/solar install which would probably actually push most people towards it
IMO we don’t place enough emphasis on the gain in comfort: my home is a solid 21°C at all times since we replaced our aging gas boiler. The larger radiators, lower water temperature and “always on” operation have removed the temperature swings.
Heat loss in our home is high (single skin brick), but our bills over the course of the year are on a par with having the heating running for 12h a day. They are substantially more expensive during the winter when temperatures drop below 5°C, but that isn’t noticeable when averaging the bills out over the year.
Got to do our roof in the next couple of years so solar is a natural next step for us.
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