Most efficient way to use solar?

YorkshireJames

QrizB said:

If you want to get into the nitty-gritty of optimising your heat pump, you could do a lot worse than read this thread.

Thanks, that's really helpful and very detailed, is there a guide somewhere to the maths and the terminology as I'm struggling to understand.

What are the main technical figures I need, and how do I do the calculations for:

- Ground source heat pumps
- Solar water panels and immersion heaters

- Underfloor heating

- Solar PV
?

Everything I read is either basic guides with no calculations or super technical reports?

Thanks so much for your help.

Phlik

YorkshireJames said:

Thrugelmir said:

How often does the sun shine when you need your heating on? 

Probably not that often. I'd estimate we need the heating on majority of the time when it's dark. We're on economy7, so that should make things cheaper, or should we buy a solar battery for evening heating?

If there's not enough sun for the panels to run the ashp then they can't charge the battery either.

Solar panels to run your heating in winter is a complete none starter.

Verdigris

YorkshireJames said:

QrizB said:

If you want to get into the nitty-gritty of optimising your heat pump, you could do a lot worse than read this thread.

Thanks, that's really helpful and very detailed, is there a guide somewhere to the maths and the terminology as I'm struggling to understand.

What are the main technical figures I need, and how do I do the calculations for:

- Ground source heat pumps
- Solar water panels and immersion heaters

- Underfloor heating

- Solar PV
?

Everything I read is either basic guides with no calculations or super technical reports?

Thanks so much for your help.

As far as heat pumps are concerned, I'd recommend reading Heat Pumps For The Home by John Cantor. Written on various levels of technical detail, so definitely useful to anybody contemplating going down the heat pump road.

[Deleted User]

Phlik said:

YorkshireJames said:

Thrugelmir said:

How often does the sun shine when you need your heating on? 

Probably not that often. I'd estimate we need the heating on majority of the time when it's dark. We're on economy7, so that should make things cheaper, or should we buy a solar battery for evening heating?

If there's not enough sun for the panels to run the ashp then they can't charge the battery either.

Solar panels to run your heating in winter is a complete none starter.

You are right but a solar/battery set up can make some cost savings by storing excess solar and by making use of cheaper overnight tariffs. That said, the cost of a battery may never be recovered. Don’t forget that for every 10kWh that goes into a battery, only 8 to 9kWh comes out. The ‘should I: shouldn’t I’ maths are very complicated.

wrf12345

Economy 7 rates tend to be higher in the day than standard rates, though cheaper at night - obviously - when you do not really need the heat and if the energy rating is C most of that stored heat (not sure how you run a heat pump to store heat in radiators) will have disappeared out of the windows mid morning. Capped rates for electricity from April are circa 28p kwhour and a heat pump might only need a third of power outputted to generate the actual heat so that is close to the cost of gas at the post April rates. On a sunny day the cost of running the heat pump may be covered by the solar generated so why run it on economy 7 whose rates are probably going to be non-viable in the day. I would also look for a tariff with low standing charges as you should be able to get the general electric bill (excluding heating) way down. I would also consider buying a used 3KW fan heater (cost next to nothing) and run that on sunny winter days, equivalent to a couple of large radiators. Your estimated bill is just an estimate, I would put electric usage in at fifty percent of your current house and see how it plays out over time.

Phlik

[Deleted User] said:

Phlik said:

YorkshireJames said:

Thrugelmir said:

How often does the sun shine when you need your heating on? 

Probably not that often. I'd estimate we need the heating on majority of the time when it's dark. We're on economy7, so that should make things cheaper, or should we buy a solar battery for evening heating?

If there's not enough sun for the panels to run the ashp then they can't charge the battery either.

Solar panels to run your heating in winter is a complete none starter.

You are right but a solar/battery set up can make some cost savings by storing excess solar and by making use of cheaper overnight tariffs. That said, the cost of a battery may never be recovered. Don’t forget that for every 10kWh that goes into a battery, only 8 to 9kWh comes out. The ‘should I: shouldn’t I’ maths are very complicated.

Certainly is. I've  benefited from a 4.2kwh install here for the last few years. Batteries are just about becoming interesting, looked a few years ago and they were still to expensive for too little capacity.

ProDave

Nobody seems to have mentioned this but you HAVE taken over the FIT contract haven't you?

It is NOT just the same as signing up with your electricity import supplier.  The FIT is administered separately, and does not have to be with the same supplier.  It is probably easiest to stay on the same supplier as the FIT was with the previous owner.  And the procedure for re asigning the FIT contract is different and a little more complex.

You then submit a quarterly reading from your generation meter to your FIT supplier and they pay you quarterly for the electricity you have generated.   I would expect the FIT payments would pretty much equal your import payments.

Get that sorted out first.

THEN self usage of your generated electricity is completely separate and the more appliances you can shift to sunny daytime use the less you will import and pay for.

In my case, we use the washing machine, dishwasher and tumble dryer one at a time near the middle of the day.  Also I have set the timer on the ASHP so it only starts domestic hot water heating at 11AM so there should be good PV generation by then.

And lastly a solar PV dump controller will automatically send surplus PV to your immersion heater for more hot water heating.

markin

Im not sure if you should be on economy 7, you should do the math on if you should be on a normal tariff, The heating will be running almost 24hrs not just at night, You may even end up with a temperature set back at night so are using less power at night than day, unless the summer solar makes up for winter day costs, and you charge an EV at night in summer?

And look at going with octopus agile

https://www.energy-stats.uk/octopus-agile-outgoing-export/

jimjames

YorkshireJames said:

Thanks all. It's not a new build l, it's 15 years old and on the original feed in. So I think we would get 50% of our generated energy back through that regardless of our exported amount - am I right? 

If it's 15 years old then meter should be fine and not go backwards. If it was then you might not want to get replaced with smart meter until the last possible moment.

In terms of FIT tariffs these are fixed so there isn't any financial reason to switch to a different provider. In fact I'm not sure many even allow you to move unless you are getting electricity from them too.

YorkshireJames

ProDave said:

Nobody seems to have mentioned this but you HAVE taken over the FIT contract haven't you?

Thank you for saying this, yes we're working through the forms and apparently it will take at least 90 days for them to transfer it across but payments will then be backdated.