Energy Storage and Back-Up Power
If you have solar panels on your roof, it makes sense to add batteries too so you can store excess energy, help smooth out peaks in demand, and power the home during an outage. In theory anyways!
In practice, current home batteries are expensive and limited in capacity. E.g. Tesla powerwalls cost upwards of $12,000 each and have a capacity of 13.5 kWh. This is approx the same amount of energy as stored in a 1.3-litre bottle (~1kg) of petrol or propane, or 1/3 a gas station bundle (~3kg) of firewood! Source: Mackay: Sustainable Energy without the Hot Air. In other words, one battery might cover electronics and lighting during an outage, but would only last a few hours if you added heating / cooling / cooking.
By comparison, the typical battery in an electric vehicle is 4-5x the size. Our Kia has a battery capacity of 60 kWh. If you already have an EV sitting in your garage, why not use this for backup power?
The challenge is that vehicle-to-home (V2H) isn’t really available yet. Most EVs are designed to draw electricity from a charger, but not run bi-directionally. A few exceptions on the market are the F-150 Lightning and Tesla Cybertruck. Vehicle-to-load (V2L) is becoming more common – Hyundai’s Ioniq and latest Kia Niro both let you plug a cable into your EV to charge devices. But V2L is not intended for home backup power.
Several companies are trying to crack the problem of V2H or Vehicle-to-grid (V2G) which has huge potential by and large. But the technology, distributed power strategy and alignment of incentives are complicated and still a few years out.
In the meantime, what’s the best way to wire a home for EV as battery back-up? We’ve decided to separate circuits into a whole home and an essentials panel that covers plug circuits, lights, fridge/freezer etc. We installed a transfer switch so that during an outage, this panel can be isolated from the grid and fed from a back-up source. If the power goes out, we’ll plan to use a high efficiency wood stove for heating, a camp stove or propane BBQ for cooking and - for now, a small portable electric battery for devices. In future, our electrical circuits should be ready to use backup power from our EV via V2H🤞✅
#netzero #netzerohomes #greenbuilding #sustainability #ev #solar #distributedenergy #backuppower #V2L #V2H
