COP - diminishing returns on investment?

Reed_Richards

I don't have a flow rate meter to measure water flow and AFAIK my heat pump does not report a flow rate. 

The L&G T230 seems to cost around £100 if bought on eBay and it might not serve any practical purpose, in which case we are back at the start looking at how much money you should pay for a given SCOP improvement.  

michaels

This is interesting. 

Obviously the 10 year time horizon as mentioned is probably too short - I suspect the entire heating system would last 50? years with perhaps 1 or 2 heat pump replacements needed during that period/  Similar output heat pumps seem to cost between 3k and 7k, I suspect the difference in SCOP might not justify the cost of a more expensive, more efficient one although there is also potentially differential longevity.

I think If i replaced 9 of 16 rads I would be able to reduce my max flow temp from 50C (-5c) to perhaps low 40s.  Obviously the win from lower flow temp is biggest when it is coldest, once the temp gets to +5c the flow temp is only just over 40 (now) and perhaps 35 with more rads at which point the savings in terms of both energy usage and the difference in efficiency decline.

I would change the rads myself so only need to factor in the purchase cost.  We are a big user, perhaps 14k of space heat per year (heating only by heat pump currently) but because of having about 80kwh of battery storage our price per unit is only about 8-9p.

FreeBear

Reed_Richards said: The L&G T230 seems to cost around £100 if bought on eBay and it might not serve any practical purpose, in which case we are back at the start looking at how much money you should pay for a given SCOP improvement.  

The last one I picked up was only £18. Quite a good bargain. You'll often find L&G heat meters under different brand names. This one looks to be a decent buy -> https://www.ebay.co.uk/itm/205031412984 - Includes fittings which would otherwise push the final price up.

The alternative is something like a YF-B7 flow meter, plus temperature sensor in the flow pipe plus an ESP32 to process the raw data. Or if you feel like taking a punt, several ultrasonic heat meters over on Aliexpress from £20 (plus VAT & shipping).

stripling

FreeBear said:

Reed_Richards said: The L&G T230 seems to cost around £100 if bought on eBay and it might not serve any practical purpose, in which case we are back at the start looking at how much money you should pay for a given SCOP improvement.  

The last one I picked up was only £18. Quite a good bargain. You'll often find L&G heat meters under different brand names. This one looks to be a decent buy -> https://www.ebay.co.uk/itm/205031412984 - Includes fittings which would otherwise push the final price up.

The alternative is something like a YF-B7 flow meter, plus temperature sensor in the flow pipe plus an ESP32 to process the raw data. Or if you feel like taking a punt, several ultrasonic heat meters over on Aliexpress from £20 (plus VAT & shipping).

All these things are great if you can fit them yourself but if you have to pay an electrician to do it it's pretty expensive. Plus for stuff like ESP etc., it needs a heat pump geek... 

I saw the Shelley in the sales at a really good price but I can't fit it...  🤦🏻‍♀️

QrizB

michaels said:

Obviously the 10 year time horizon as mentioned is probably too short - I suspect the entire heating system would last 50? years

Just on that point, I didn't choose 10 years as the life of the system. 10 years represents a ~7% return on investment. If you had £1k in a SSISA and earning 7% (eg. you were invested in UKWIND) then over 10 years it would earn you another £1k.

Spending £1k to improve your COP means you're missing out on that £1k of returns over the next decade. So it's an approximate way to judge whether it's worth spending to cut your bills, or whether you should just keep the money invested and buy more electricity.

If I'd chosen 50 years, that's only a 1.4% return which is (in my opinion) unrealistically low.

I acknowledge (again) that you might not choose to look at this in purely financial terms, but this is the Money Saving Expert forum not the Planet Saving one.

FreeBear

stripling said:

FreeBear said:

Reed_Richards said: The L&G T230 seems to cost around £100 if bought on eBay and it might not serve any practical purpose, in which case we are back at the start looking at how much money you should pay for a given SCOP improvement.  

The last one I picked up was only £18. Quite a good bargain. You'll often find L&G heat meters under different brand names. This one looks to be a decent buy -> https://www.ebay.co.uk/itm/205031412984 - Includes fittings which would otherwise push the final price up.

The alternative is something like a YF-B7 flow meter, plus temperature sensor in the flow pipe plus an ESP32 to process the raw data. Or if you feel like taking a punt, several ultrasonic heat meters over on Aliexpress from £20 (plus VAT & shipping).

All these things are great if you can fit them yourself but if you have to pay an electrician to do it it's pretty expensive. Plus for stuff like ESP etc., it needs a heat pump geek... 

I saw the Shelley in the sales at a really good price but I can't fit it...  🤦🏻‍♀️

A heat meter wouldn't need an electrician (no mains voltages to wire up). Any decent plumber or handyman could fit one pretty quick.

As for the ESP stuff, yes, it does require a bit of geekiness. But if you are already disappearing down the rabbit hole of collecting data, it is just a small diversion

lohr500

Lots to consider, but to be controversial, based on current gas and oil prices, other than for environmental reasons, I see little incentive to switch to a heat pump.

10MWh of heat based on the EDF SVT gas price of £0.063 in our region would cost £7000 over the 10 years at 90% efficiency..

10MWh based on the oil price of £0.65 per litre would cost £6978 over the 10 years at 90% efficiency and at 10.35kwh per litre.

Yes, you need to consider the drive to ban gas and oil heating and the impact this will have on relative fuel costs over the 10 year window.

And it would depend if your existing boiler needs replacing anytime soon and the relative cost of doing that vs a heat pump installation.

Plus I am sure lots of other valid points in favour of or against switching to a heat pump.

My biggest fears (probably unfounded) are : :

The ability to fine tune the heatpump so that a COP of 3.5+ is achievable.
The long term reliability of heat pumps.
The cost of electricity as the state monopolises the UK's choice of power through the banning of gas/oil boilers and fossil fuel vehicles.

Faced with having to replace our oil boiler today, I would still go for oil again.

FreeBear

lohr500 said: My biggest fears (probably unfounded) are : :

The cost of electricity as the state monopolises the UK's choice of power through the banning of gas/oil boilers and fossil fuel vehicles.

Faced with having to replace our oil boiler today, I would still go for oil again.

Energy prices will continue to rise. There are rumblings & talk of removing green levies on electricity and putting them on gas instead (and possibly heating oil too). This would make gas & oil relatively more expensive compared to electricity. Any relative increase in gas/oil prices will shift the balance in favour of heat pumps.

If I had to replace my gas boiler today, I'd give heat pumps serious consideration. Having been running with lower flow temperatures this winter, I'm reasonably confident that an ASHP will work with minimal changes.

michaels

QrizB said:

michaels said:

Obviously the 10 year time horizon as mentioned is probably too short - I suspect the entire heating system would last 50? years

Just on that point, I didn't choose 10 years as the life of the system. 10 years represents a ~7% return on investment. If you had £1k in a SSISA and earning 7% (eg. you were invested in UKWIND) then over 10 years it would earn you another £1k.

Spending £1k to improve your COP means you're missing out on that £1k of returns over the next decade. So it's an approximate way to judge whether it's worth spending to cut your bills, or whether you should just keep the money invested and buy more electricity.

If I'd chosen 50 years, that's only a 1.4% return which is (in my opinion) unrealistically low.

I acknowledge (again) that you might not choose to look at this in purely financial terms, but this is the Money Saving Expert forum not the Planet Saving one.

Personally I would not expect a risk free real return on investment of more than about 0.5%

QrizB

michaels said:

QrizB said:

michaels said:

Obviously the 10 year time horizon as mentioned is probably too short - I suspect the entire heating system would last 50? years

Just on that point, I didn't choose 10 years as the life of the system. 10 years represents a ~7% return on investment. If you had £1k in a SSISA and earning 7% (eg. you were invested in UKWIND) then over 10 years it would earn you another £1k.

Spending £1k to improve your COP means you're missing out on that £1k of returns over the next decade. So it's an approximate way to judge whether it's worth spending to cut your bills, or whether you should just keep the money invested and buy more electricity.

If I'd chosen 50 years, that's only a 1.4% return which is (in my opinion) unrealistically low.

I acknowledge (again) that you might not choose to look at this in purely financial terms, but this is the Money Saving Expert forum not the Planet Saving one.

Personally I would not expect a risk free real return on investment of more than about 0.5%

That's your choice, but this isn't a *real* return; it's a nominal one.

I'm not competent to explain discounted cash flow, but there are some good articles if you want to read about it on the internet. There's even a Wikipedia page.