Adding a battery to existing solar.

Screwdriva

https://forums.moneysavingexpert.com/discussion/comment/81941067#Comment_81941067

All valid (and debatable) points.

SEG tariffs could go down. Or they could continue to drift higher. It's impossible to be predict accurately but it is somewhat likely they will trail import tariffs proportionately, and these have continued to rise over the past decade. If I had to bet, I believe both will occur simultaneously i.e. export will become less rewarding from 11am-2pm on summer days as the grid saturates with renewables, but the morning/ evening peak grid events will remain extremely lucrative for "smart" export tariffs. EV discounted charging windows will likely go down the " Intelligent Agile" incoming route as transportation continues to electrify.

Batteries are indeed oversold. I only recommend the Powerwall 3 because I've seen how well the PW3 performs and how well Telsa treats its long term battery customers in the UK, relative to other battery brands. That said, import and usage requirements should yield a return on investment within a decade for me to suggest investing in one, and is the only reason why I don't yet own one. If I'm right, it won't be long before that changes.

LateStarter

https://forums.moneysavingexpert.com/discussion/comment/81941067#Comment_81941067

I agree that many people's assumptions need a second look. But opportunity cost of cash is a difficult one - in my case I paid for the panels on a 0% credit card. The card is being paid off from the saving/SEG in spring to autumn months - what I pay is winter is what I would have paid in winter anyhow. My payback time is 6-7 years, without a penny in outlay. After that time, my summer gains will greatly reduce the winter costs.

Nick_Dr1

Its a fluid situation. I followed the same route as LateStarter and put solar and battery on a zero percent credit card. I then treated it as a loan over the period of the interest free period (31 months) and added notional loan repayments monthly to a stocks and shares ISA. That was the basic idea but it has tweaked itself a bit over the years. Fitted in March 2022. Broke even a couple of months ago due to Ukraine war early on, and good performance of the stock market afterwards (and a good tariff!) . Water was muddied by fitting a heat pump 18 months ago, thereby going full electric and although I wasn't actually expecting any overall saving from that, it has cost me less over the year compared with oil. Even more so now!

Could have gone the other way, but every time there is an energy crisis, I (will) think good job we fitted solar and a heatpump. You do need a crystal ball if you are worried about payback, but even with a battery it will pay back eventually whatever the cost. Payback considerations for the heatpump were never even thought about. I just wanted to get rid of oil, and the boiler and tank were old. Every situation is different though.

NedS

Similar experience here. The first year of operating our heat pump, the running costs were around half of the oil boiler it replaced. Adding a battery this year, and thus reducing our unit cost of import will reduce that further.

Looking at the situation right now, our running costs for heating and hot water for this March are £41. If we had a gas boiler, the same amount of heat would have cost us £88.80, and if we still had our old oil boiler, based on the current cost of oil it would have cost us £215.

Looking at the way we run our home, it is important to look at the whole picture, ASHP, Solar and battery in combination. In winter, the battery reduces the overall unit cost of import by allowing us to run on cheap rate ToU tariff, but a far greater contribution comes from the fact it gives us access to IOF in summer which effectively doubles the price we receive for export. Last summer on IOF we achieved an average 26p/kWh for export meaning for every kWh we exported in summer, we could by back 1.75kWh (at 14.7p) this winter. That leverage has allowed us to move from having annual bills of over £2500 (and that was before Ukraine!) to having zero bills or having Octopus pay us each year. Big picture.

LateStarter

My own experience is SEG rates are dropping - when I signed up to EoN last September, I got 16.5p; their current deal is 13p. Octopus Outgoing has dropped to 12p. So payback period may/will be more than 7 years. Now I'm considering an EV - as opposed to a battery - at that gives me access to cheap night rates to run appliances on (not sure how much difference that will make).

So - EV vs Battery - which way would you lean?

Screwdriva

"Dumb" SEG tariffs were dropping. My recent conversation with a senior Octopus executive highlighted that they are looking at reversing this, as well as opening up the Flux tariffs again, once the balance sheet regains health. Pretty obvious that it's going to be a very volatile year for energy.

As with all batteries (an EV is a battery with 4 wheels), it largely depends on consumption. How many miles would you drive per year?

A used EV makes much more sense (early Model 3 Teslas were going for < £13K not too long ago. Not sure how much longer that will last).

LateStarter

https://forums.moneysavingexpert.com/discussion/comment/81944219#Comment_81944219

We run 2 cars (both petrol). A 5 year old Nissan Leaf is about £10k, and would replace my car, used 90% of the time for short runs, probably 6k miles per year.

Screwdriva

https://forums.moneysavingexpert.com/discussion/comment/81944231#Comment_81944231

When comparing to a Powerwall 3 at £7K, the Leaf does appear to make some sense. If you're feeling adventurous, it is one of the few EV's that have vehicle to home/ grid capability and access to Octopus Power Pack.

Martyn1981

https://forums.moneysavingexpert.com/discussion/comment/81944173#Comment_81944173

Your headaches have only just started! Once you go EV, as you say, that opens the door to cheap(er) rate night leccy. But having made that shift worthwhile, you now have access to super cheap HP heating of the house during the night, and you can provide daytime leecy at night rates via a home battery.

The beauty is that each item (PV, batts, HP's, cheap rate, EV's) all lean on each other, making the argument for each (and all) stronger. Possibly the perfect illustration of the whole being greater than the sum of its parts. And whilst export rates have just gone down for me from 15p to 12p, import rates are dropping from 7p to 5.2p. So whilst I was somewhat saddened to see that my export would no longer cover my entire energy bill (£600 £480 v's £600), looks like my leccy bill may drop ~£100 now.

Off to buy some paracetamol!

Heedtheadvice

Yes Martyn, lots of opportunities but eggs and baskets come to mind with a single electrical basket!

I have written sometimes about supply failure risk on some threads but irrespective of the cause as we can see currently as well as historically the Financial side has several uncertainties, both positive and negative.

( electrical puns unintended!!)