Battery with heat pump but no solar - your thoughts

NedS

HorseWhisperer said:

Reed_Richards said:

I replaced an ageing oil boiler with a heat pump.  I really like the heat pump but it's not saving me a lot of money in heating costs because oil is so much cheaper per kWh than electricity.  So even though the heat pump will, on average, give me 3+ kW of heat per kW of electricity, if I buy electricity at the standard rate that still works out at much the same running cost as an oil boiler.  This is exactly what I did for the first few years but now I have a cheap overnight rate which works out better.    

I'm not expecting a heat pump to save us much, if anything. I just want a house that's warm all the time and I don't have to sit in a sleeping bag in deep mid-winter! So long as it just about breaks even, that's fine by me. There are really good tariffs out there now, especially if you want to charge up a battery in winter overnight. Thanks for sharing your experience :-)

One of the best tariffs for a heat pump and battery is Octopus Cosy, as it gives three cheap slots spread out throughout the day, with never more than 6 hours to the next cheap rate slot. This means you get 8h of cheap rate electricity spread over three periods to charge and discharge your battery which should allow you to run a heat pump continuously at the cheap rate price. With a bit of careful management, you could probably cover 50-60kWh usage per day with a Tesla PW3 on Cosy (this is our plan for next winter if our G99 application every gets approved). With a cheap rate overnight tariff, your battery will likely be empty by lunchtime in winter unless you can afford to stack multiple batteries. Such a tariff may work OK at other times of year where daily usage does not exceed battery capacity, but for most installing sufficient battery capacity to cover a full day's usage in winter is prohibitively expensive.

As per the above, if you can significantly cut your electricity import costs, a heat pump can halve your heating costs. During the very coldest periods over the winter we were paying no more than the oil boiler we replaced, and for the rest of the time the heat pump is substantially cheaper to run. If we can reduce our import costs further with a battery, we expect significant further savings in winter.

Patrol

Overnight electricity into a battery isn't going to cover your existing consumption plus a heatpump. Cosy would be much better in this respect as mentioned by NedS

I'm not sure why a heatpump would make your house warmer all the time than is achievable with your current system unless the boiler is ancient or defective. Running the boiler 12-18 hours a day is probably no worse than having a heatpump running 24/7

Solar and battery will save you money. Spend the difference on keeping your house warmer, then work out how a heatpump will affect it once you are in a position to act on that

Many (all?) solar installers provide an expected annual savings breakdown as part of a no obligation quote. At least consider this and ask them if there are any complications of doing battery first and solar later as that's fairly unusual and I'm not sure if there is some VAT implication on the battery (plus there might be 2 sets of costs + profit if done as 2 installs that they reduce margins on if done together)

thevilla

Batteries are zero vat rated since, I think,  Feb 2024.

michaels

Patrol said:

Overnight electricity into a battery isn't going to cover your existing consumption plus a heatpump. Cosy would be much better in this respect as mentioned by NedS

I'm not sure why a heatpump would make your house warmer all the time than is achievable with your current system unless the boiler is ancient or defective. Running the boiler 12-18 hours a day is probably no worse than having a heatpump running 24/7

Solar and battery will save you money. Spend the difference on keeping your house warmer, then work out how a heatpump will affect it once you are in a position to act on that

Many (all?) solar installers provide an expected annual savings breakdown as part of a no obligation quote. At least consider this and ask them if there are any complications of doing battery first and solar later as that's fairly unusual and I'm not sure if there is some VAT implication on the battery (plus there might be 2 sets of costs + profit if done as 2 installs that they reduce margins on if done together)

It does for me meaning I pay 8p per unit on average which is a lot cheaper than cosy - then again I have v2g and pup to 80kwh of storage to call upon.

HorseWhisperer

Patrol said:

Overnight electricity into a battery isn't going to cover your existing consumption plus a heatpump. Cosy would be much better in this respect as mentioned by NedS

I'm not sure why a heatpump would make your house warmer all the time than is achievable with your current system unless the boiler is ancient or defective. Running the boiler 12-18 hours a day is probably no worse than having a heatpump running 24/7

Solar and battery will save you money. Spend the difference on keeping your house warmer, then work out how a heatpump will affect it once you are in a position to act on that

Many (all?) solar installers provide an expected annual savings breakdown as part of a no obligation quote. At least consider this and ask them if there are any complications of doing battery first and solar later as that's fairly unusual and I'm not sure if there is some VAT implication on the battery (plus there might be 2 sets of costs + profit if done as 2 installs that they reduce margins on if done together)

We consume 1600 litres of oil at a cost of approx £1200 annually, but only run the heating for 5 hours a day and heat water for 2 x 1 hour in 24. To double the heating would costs us around £2000 annually. Our electricity bill is already approx £1,500. We don't really want to double the amount of emissions we're producing or give any more money to the oil barons. The idea is to try and bring our energy costs per KwH down rather than increase them and eventually become more self-sufficient.

HorseWhisperer

michaels said:

  I have v2g and pup to 80kwh of storage to call upon.

Sorry - could explain this bit. Mumbo jumbo to a newbie like me ;-)

Reed_Richards

HorseWhisperer said:

michaels said:

  I have v2g and pup to 80kwh of storage to call upon.

Sorry - could explain this bit. Mumbo jumbo to a newbie like me ;-)

@michaels is one of a very very tiny minority with the capability to use their electric car battery to power their house, instead of having a dedicated home battery like the rest of us.  If everyone with an EV could do this it would be really beneficial in helping to balance the load on the grid - so the government has done nothing whatsoever to encourage it happen and there has been no progress in years.

"v2g" is Vehicle to Grid
"pup" I presume is a misprint for "up"
Their car must have an 80 kWh battery (or they have more than one EV).   

HorseWhisperer

@michaels is one of a very very tiny minority with the capability to use their electric car battery to power their house, instead of having a dedicated home battery like the rest of us.  If everyone with an EV could do this it would be really beneficial in helping to balance the load on the grid - so the government has done nothing whatsoever to encourage it happen and there has been no progress in years.

"v2g" is Vehicle to Grid
"pup" I presume is a misprint for "up"
Their car must have an 80 kWh battery (or they have more than one EV).   

Persuading my OH to get an EV at next car upgrade is currently a non-starter :-( Hopefully the EV market will catch up with "charging home from car battery" thing as it makes sense to me.

michaels

Reed_Richards said:

HorseWhisperer said:

michaels said:

  I have v2g and pup to 80kwh of storage to call upon.

Sorry - could explain this bit. Mumbo jumbo to a newbie like me ;-)

@michaels is one of a very very tiny minority with the capability to use their electric car battery to power their house, instead of having a dedicated home battery like the rest of us.  If everyone with an EV could do this it would be really beneficial in helping to balance the load on the grid - so the government has done nothing whatsoever to encourage it happen and there has been no progress in years.

"v2g" is Vehicle to Grid
"pup" I presume is a misprint for "up"
Their car must have an 80 kWh battery (or they have more than one EV).   

All correct including the 2 car bit - just had to swap them over now as one had run down today due to it being coldish and little PV.

Our oldest EV had its tenth birthday today.  We didn't do cake and candles but I will be picking my son up in it in a minute, adding to the 96k miles it has done.

Patrol

michaels said:

It does for me meaning I pay 8p per unit on average which is a lot cheaper than cosy - then again I have v2g and pup to 80kwh of storage to call upon.

Fair point, if you have large battery capacity. Is there a restriction on transfer rate from the car, e.g if household demand is 3-4kWh can v2g support all of that