Solar PV with or without battery?

pensionpawn

Screwdriva said:

Reed_Richards said:

It wasn't meant any other way.  But I'm not sure I would do as well as you with the same hardware.  For one thing, I don't think I could persuade my other half to have a cooked meal only at lunch time and not use the hob and the oven during the Flex peak hours.  

If I tried that on my other half, I'd be single again!

The only changes we've made have been 1) running all cleaning appliances (washer/ dishwasher/ dryer) during the 2-5am window 2) Replacing all appliances with the most efficient option sold on the market when the time comes. 

My wife isn't yet (although she's slowly mellowing over time...) a fan of cooking at lunchtime however we have found that it has other benefits on top of reducing your energy bill. For example, no snacking / nibbling mid morning / afternoon and a good excuse to get out of the house (exercise) from early afternoon until dusk. The dishwasher and washing machine are also programmed between 2am - 5am. Finally, as already mentioned, use low energy appliances and I bought a load of Smart timer switches to switch off all non essential electrical black holes overnight, automatically switching them back on again for breakfast.

Reed_Richards

pensionpawn said:

Not an outlier... I replaced my 26 year old boiler a year ago with a Viessmann hydrogen ready condensing model. It has almost halved my gas consumption. Replaced my 25 year old windows the year before, which also approximately halved my CH gas consumption. The next big win is a change of lifestyle to cook (electric oven / induction hob), where it's convenient, around noon. This also minimises import / maximises export (on Flux). It's a plan, over many years and not without up front cost, however the goal is to nail down my outgoings for when we're both fully retired. Not long to go!

Okay, I can believe that a 26 year old gas boiler could be so inefficient that a modern condensing boiler run at lower output temperatures might halve your gas usage.  But 25 years doesn't seem old for windows; I find it hard to believe that you were losing so much more heat through the old ones than through the new.  How did this come about: did you replace single-glazed with triple glazed?  Or do you use trickle vents now instead of opening the windows?    

pensionpawn

Reed_Richards said:

pensionpawn said:

Not an outlier... I replaced my 26 year old boiler a year ago with a Viessmann hydrogen ready condensing model. It has almost halved my gas consumption. Replaced my 25 year old windows the year before, which also approximately halved my CH gas consumption. The next big win is a change of lifestyle to cook (electric oven / induction hob), where it's convenient, around noon. This also minimises import / maximises export (on Flux). It's a plan, over many years and not without up front cost, however the goal is to nail down my outgoings for when we're both fully retired. Not long to go!

Okay, I can believe that a 26 year old gas boiler could be so inefficient that a modern condensing boiler run at lower output temperatures might halve your gas usage.  But 25 years doesn't seem old for windows; I find it hard to believe that you were losing so much more heat through the old ones than through the new.  How did this come about: did you replace single-glazed with triple glazed?  Or do you use trickle vents now instead of opening the windows?    

From my meter readings, for the 12 months immediately prior to my new windows installation I consumed 12.1 Mwhrs of gas. For the 12 months immediately after installing new windows, I consumed 9.1 Mwhrs of gas. OK, so my "off the top of my head" figures were slightly off (by almost a factor of 2 lol) however even a 25% reduction makes a decent impact on the annual energy bill. Our windows were already double glazed (1996 new build) however the frames were perishing and quite drafty. The new windows also having better thermal qualities. It all adds up, and who wants to have these expensive jobs cropping up 10+ years into retirement.

ABrass

All you needed to say was draughts.  As soon as you get them then it doesn't matter if it's triple glazing or single glazing.

Screwdriver is good at energy saving. Not as good at money saving though. 

Qyburn

I'm surprised a 25 year old boiler would be only 50% efficient.  

1961Nick

Qyburn said:

I'm surprised a 25 year old boiler would be only 50% efficient.  

70% is probably more typical for a well maintained 25 year old non condensing boiler.

pensionpawn

The new boiler was installed because from past experience the old one wasn't going to survive another prolonged cold snap. With a solar divert for hot water during BST its original main role being CH & HW only during GMT. However since the launch of Flux earlier in the year I've ditched the solar divert to maximise paid export with the new super efficient boiler taking over the HW role throughout the year. A win / win with the unexpected outcome of a rise in my gas usage since Spring, although obviously much reduced compared to what the old boiler would have churned through. So, I would recommend to the OP to leave the battery for now, and given the time of year and your peak usuage times, as others have suggested select Octopus flat rate export with a view to moving to Flux when we enter GMT next spring.

Screwdriva

ABrass said:

Screwdriver is good at energy saving. Not as good at money saving though. 

That's the nicest thing anyone has ever said about me on these forums! Such a charmer!

pensionpawn said:

However since the launch of Flux earlier in the year I've ditched the solar divert to maximise paid export with the new super efficient boiler taking over the HW role throughout the year. A win / win with the unexpected outcome of a rise in my gas usage since Spring, although obviously much reduced compared to what the old boiler would have churned through.

We experienced a similar result (31% net gas reduction) when we switched to a Viessmann 200-W gas boiler, replacing our 5 year old Worcester Bosch Greenstar system boiler. Like you, our focus is now on the maximum PV export possible, to build up that Octopus credit. 

Reed_Richards

But if you want to export even more you could charge up a battery at the cheap night import rate then discharge it at the peak evening export rate.  

pensionpawn

Reed_Richards said:

But if you want to export even more you could charge up a battery at the cheap night import rate then discharge it at the peak evening export rate.  

....I agree, the advent of Flux is now cleverly moving the primary use of batteries from just avoiding random imports firmly into the function of skewing energy demand away from the current daily peak. Quite sensible from a national energy dimensioning / balancing point of view, especially through winter. However if you buy a battery based on a tariff like Flux and that tariff is withdrawn, or changed in a way that no longer benefits, what then? Well you're back to just avoiding random imports, which may have a very long RoI...