Heat pumps for hot water

You might possibly get say a COP of ~ 3.0 ("300% efficiency") overall if you only heat to 45C with one weekly increase to 60C for legionella protection. I am paying ~ 30c/kwh for Elect just now so if all the water is been heated at full cost then 30C/kwh or ~ 15C/kwh for night rate, effectively becomes 10C/kwh & 5C/kwh. I paid 140C/liter for oil, last fill in March. If you allow ~ 70% boiler efficiency on HW heating only, then the cost becomes 19.4C/kwh, you might want to factor in cost of replacement unit/compressor every 8 years or so and while a gas/oil boiler might be somewhat similar (but every 10/15 years) you are also running the CH off this so probably shouldn't factor the boiler replacement cost?.

If you assume DHW requirements at 200LPD at 45C (from cold water at average temp of 10C) then energy requirement is 8.14kwh + say 1.5kwh/day for cylinder losses, total, 9.64kw/day or 3519kwh/year. Heat pump cost €352 or €176. Oil cost €603, simple pay back time, 2600/(603-352), 10.4years or 2600/(603-176), 6.1 years.

First point, yes, day vs night rate.

Normal electric immersion will cost you 30C or 15C per kwh, so day rate cost, €1056/year, night rate €528/year.

And your heat pump will be busy after around 8 years.

Meaning you will have no payback as you will have to buy a new one.

They are a con job, not fit for Irish weather.

? 8:48 might be a bit early for you.

So they are fit for what 'weather' then? If it's German 'weather' that they are fit for, consider that Germany have a lower average Winter temperature than us, so please enlighten us further.

Is that saving based against oil or gas or electric immersion cylinder heating?.

Just to call bullsh*t on some of the figures touted on this thread, particularly the one that compares the cost per kwh of heat from a heatpump, compared to oil, and has the heatpump at just over half. Its claimed the kwh cost of the heat pump HW is 10 cent/kwh. This must be based on the fantasy 4 to 1 return per kwh of the heatpump, and 40c per unit for the electricity.

It's then claimed oil will cost 71% more, about 17cent/kwh. Last time I looked a litre of kerosene had an energy output of 10.35kwh per litre. Having just paid 1.13 for a litre, and with a highly efficient 93% condenser boiler (especially if I only allowed flow to heat to a measly 45°), I make that about 12c/kwh. In cold weather you will struggle to get a COP of over 2 on your heat pump. If you're paying 50c/kwh for your daytime rate, as punishment for cheaper night rate, then your heatpump HW is costing 25c/kwh. Double, not half of your oil boiler. Add the massive installation and depreciation costs of heat pumps, its a waste of money.

Biggest joke, the electricity you are consuming in this heatpump is currently close to 90% generated by burning mostly gas, but also oil. 55% of the gas heat and 62% of the oil heat is lost in the generation process, and a further 5% of whats left is lost over the transmission lines to your home. So much for lower carbon ar&e print. Its nonsense to ban burning gas ( or oil) directly in your home in a cheap efficient burner which can be installed for as little as a grand for gas. The eco bull continues to be peddled though. We are so far away from independence from fossil fuels, we should just face reality. Pour all the grant money into insulation and passive homes, and burn the tiny amounts of gas needed in them.