Michael_S

Sorry for not being clear, the minus 7 was an example arbitrary personal decision on what outdoor temp you want to be able to cover, I can see this was not clear. Obviously there are the MCS 'rules' based on a set room temp, outdoor temp (by geography) and number of bedrooms which I guess become a minimum if you want the grant but you could obviously decide you want to exceed these to support more hot water or higher room temps or a lower minimum outside temp.

Very impressive heat loss. In theory that outside air temp is actually slightly lower than the heat pump design standard. For heat pump sizing you need to find out if a quoted x kw at -7 (or whatever you decide your actual min point should be) includes defrost cycles. You obviously also need to factor in hot water demand, we do hot water via immersion so know that the 5 of us use more than 25kwh per day so at least 1kw per hour to add on to the space heating demand.

Your boiler is probably about 95% efficient including the hot water cycle so need to downrate the gas consumption by about 5%| Do you know if your cylinder has a suitable coil for ASHP? How far is the installation location from your main consumer unit? Heat pump warehouse has suitably sized Viessman for about 5.5k inc vat - not sure if it is not the ex vat price that the installer will pay, plus any discount they have negotiated. https://www.theheatpumpwarehouse.co.uk/product-tag/viessmann/

OP said they already had 30kwh battery. There is a cycle life and therefore a cost per cycle and of course cycle efficiency to update my first order approximation.....

Suppose the heat pump gets a cop of 4 (not impossible given the low flow temps you are already operating at) 14.3k gas usage at 5.5p per kwh costs £786pa 14.3kwh gas input at 95% efficacy gas boiler divided by a cop of 4 at 7p per unit off peak rate using battery timeshift costs £238pa In theory your heat pump install should be cheap, only need a small unit (6kw?) and only change to plumbing might be to replace the hot water tank with a large coil one and hopefully your battery would be big enough to timeshift your total demand even on the coldest days? Risk is that the new govt plan to prioritise batteries may lead to a reduction in the potential savings from timeshifting due to increased arbitrage.

WE have an older series that has a paddle flow switch. My initial thought might be that you have TRVs that were closing down the flow but with a 4 pipe buffer this should not be the issue. I assume there isn't a mixer valve in the circuit somewhere that is for some reason set to a low value?!

The only supplier I have found with good info on modulation is Viessmann where they show a shaded 'output area' for min and max output at each OAT temperature, possibly even different charts for different flow temps.

WE are also on the 7 hour eon tariff (6.7p) and with V2H and 2 EVs we use up to about 80kwh from batts for our heat pump and general usage in the day rate period. Likely to try for utility warehouse E7 tariff when our eon ends in May, not sure about export at that point.

Wow £1500 compensation for a financial loss probably running in to the 100s of thousands Perhaps if proper levels of compensation (ie to cover the actual loss) were paid the maths would change for these projects but that is only right.

Interesting to see so much rewriting of history- the exact bits depending on which side of the political divide you sit. I think we need a better way of compensating for nationally important infrastructure. If I was going to get a pylon at the end of my garden that would reduce my house price by 200k but was not close enough to get compensation then I would be pretty peeved at being the one who had to take the hit for the greater good. Yes expensive, but why should the national interest mean unlucky individuals?!

I guess reinforcing local grid is an issue for the DNO not the energy supplier so the economics becomes more complicated. I also guess in theory the more short term storage is available the more prices will be arbitraged across the day and thus the less financial gain will be possible from possessing a battery - so the big differences between day and night rates will become a thing of the past and the return on battery systems will fall?

You might ask why we have put in place CFDs for the build out of wind that has no route to market? Surely a self-inflicted wound?

Could be wrong but I read it as 15 cells at 3.2v (48v total) making up a total of 314AH - so 15kwh Then 6000 15kwh cycles (actually more likely 13.5kwh) is 81mwh total throughput for the money

1140 for the batts SEPLOS V4 Kit and x16 Cornex 314Ah Bundle

IS it not possible to get 15kwh of battery for £1500 and £500 for an invertor? - that electricity can then give you 45kwh during the day from your heat pump?

There seems to be an odd puritanism with regards to AC. It is apparently fine not to want to feel too cold but want to not feel to hot and you are a selfish climate wrecker.

People chose to invest in a potentially risky new technology based on and agreed set of returns. Which other contacts should the govt renege on? I am a civil servant, you probably think I am overpaid and the government should unilaterally cut my salary including for the work I have already done this month?

Logically I think you are right but in reality people seem to be very short-sighted and only look at the up front cost - se for example EVs.

We had a weather comp boiler that modulated down to under 2kw and heated 24/7 with night time set back, the curve went to about 55 flow at -10 when it ran at about 7.5kw constant. WE had hot water tank in the loft so only needed a 18kw boiler which gave the good modulation. Funnily enough now with an oversized heat pump and a heat demand when it is mild of about 1-2kw we get a lot more cycling than we did with the boiler....

EVDB says 165 winter, 210 summer at 70mph. IMHO if you have home charging then the range number that matters is range while travelling at long distance journey speeds, being able to get 240 around town makes no odds.

So if it takes 2kwh of gas to generate 1kwh of electricity at the home (60% efficiency, transmission losses), then how come that kwh of electricity does not cost about twice what a kwh of gas does - we need some allowance for the cost of the gas-fired power station but I believe this is not huge on a per unit basis and perhaps the electricity transmission grid costs more per unit than gas transmission? - but still doesn't explain why electricity is more like 4x the cost of gas? So here is a suggestion. Given heat pumps give 50% more heat output per unit of gas (50% loss in generation and transmission but 3x gain in COP) why not have a heat pump meter and charge electric units used by the heat pump at 2x the cost of a gas unit (and build the necessary gas generation to support this knowing that by speeding up heat pump roll out we are reducing our carbon footprint)

Depends a bit how efficient you think a gas boiler is in terms of KWH of gas per kwh of heat.

Depends a bit how efficient you think a gas boiler is in terms of KWH of gas per kwh of heat.

WE have a series 2 and don't think we have this option unfortunately as it sounds really useful.

Works for us with a home made install, second hand 10 year old heat pump connected to the tails of a radiator running through undersized circulation loop and immersion hot water - but of course we have a big battery (60kwh via V2H) and a 6.7p overnight tariff so a cop of 3 for heating (and 1 for hot water) doesn't matter. Total cost was about £600 but spent another £1000 this summer upgrading 7 radiators to allow lower flow temp, would have been cheaper but 5 are designer ones.