My home battery provider has optional DC expansion packs available. Briefly, this would add another 13.5 kWh to the existing 13.5 kWh netting a total capacity of 27 kWh. This would allow me to add DC capacity to my home battery system which would provide some benefits, particularly with Toronto Hydro eh, not forbidding brown exports (source). Further allowing extended operations in case of a prolonged power outage. All worth the 15k expense? Lets see.
Financially for most people, a solar-battery home energy system has never been the best investment oportunity out there. Yes you will get your money back, but if its money you want, there are better investment opportunities out there. Oh and those yield cash, not a “bill-credit” that might provide value via a lower electric bill. But the case is not exactly hopeless, lets have a peak how financially this might work out for me.
Moneywise the best thing my home battery can do is displace usage during the weekday peak hours, at 50c/kWh. The second best thing is to export to the grid during peak hours, 38 c/kWh (source). Given that my current battery system already covers my usage during peak hours, adding more, is only going to get us second place, exporting exrta 10.8 kWh (80% of the added 13.5 kWh), every weekday we could potentially add a $80 bill credit every month (assuming 21 weekdays per month). We still need to charge the battery, which is best done overnight at a cost of 7.6 c/kWh (source), while I could charge from solar, we score more credits by exporting solar at 9.8 c/kWh (weekends) or even better, 15.7 c/kWh (weekday). Hence we dock 17.23 $/month from our $80 bill credit to factor in charging, and arrive at a net-credit of $63/month. Wow, that is $756 per year, and I get my 15k back in 20 years. But, I may only have an electricity bill of $600 total this year, since I already have solar, Im earning credits March through October. So I can only really get $600 in value, so now Im getting my 15k back in 25 years.
On the other hand, my installer says he might be able to lower that price a little as winter is their quiet month, and apparently my home battery vendor has a $700 rebate (source), all that, my final bill might be closer to 10k than 15k, so now we are at 13-25 years in terms of payback. Still not the greatest investment opportunity.
Then there is vehicle to grid (V2G). Even at 27 kWh of expanded capacity, my EV has way more than that. So I could be rolling in credits if only I could somehow tap into that EV battery, perhaps for less? My home battery provider does have EV integration, but alas being Tesla, their powershare product only works if you happen to have a Tesla Cybertruck. Tesla is also rumored to be working on expanding their powershare to the Tesla Model Y, perhaps as early as middle of this year (source and source). Last I checked, a Tesla Model Y is more money than the 10-15k DC expansion pack, although we have thought about getting one, mostly to enable ski-trips further into Quebec. There are also other home battery products on the market, such as Sig Energy’s sig-store product line (source), and Dcbel’s Aura charging station (source). But again, changing out a home battery system is way more money than 10-15k. Either way, V2G is probably a good long term solution, but short term, far more costly than a DC expansion pack.
So what to do? Well, the financial’s seem to be on par with the rest of home solar situation. Might get half your money back before the system reaches end of life. There are some storm-clouds on the horizon for electricity rates in Toronto (source), we just had a rate hike last November (source), next November will likely see another one, hence the financials might be better than I think. So, its wait and see for me for now.
Electric car adventures 