The question on generators is timely. I have a very old generator that I can no longer get parts for. It no longer works. I ordered a Tesla Powerwall battery to be integrated with my solar panels to replace it. I cancelled that when I realized that the Ford F150 Lightening is designed to be a back up generator for a house. After 2 years on order, the Lightening was delivered in October. One way to use the Ford as a back-up generator (which Ford recommends) is to have their solar/battery partner, SunRun, install the battery/inverter/charger hardware for you. Unfortunately this costs $10k. However, the F150 comes with a 30A/220V electrical socket in the bed of the truck powered from its 130kWh battery. This battery is the equivalent of 9 Tesla Powerwalls. This is designed to act as a back up generator. Because of my existing (defunct) generator I already have the wiring for the emergency panel and the transfer switch. If you have had a generator in the past then you have this wiring too. I had my electrician install a connector on the side of my house which connects the truck to the emergency panel. It was a little tricky to get it running, but I now have 3 days worth of power during a grid outage. This is not running the heat pumps, I still have my oil furnace for these occasions. If I were to run the heat pumps on the Ford I would probably trip its breaker and, even if it did not trip, the battery would last maybe one day. 3 days of power is great if you are home, but we also go away for up to two weeks. The Ford’s battery will not last 2 weeks. Hence I am going to get my electrician to install an automatic transfer switch so that the Ford’s battery is only used when the grid is down.
An alternative is to install the battery/inverter/charger with your solar panels. Ask GS for a quote on this. If the battery can be recharged from the solar panels during a grid outage then even a much smaller battery (like a Tesla Powerwall) could power your house for a very long time, though probably providing enough heat from the heat pump to keep the house from freezing rather than keeping you toasty warm. Ask them what their experience is on this. Especially what happens at night (will the panels produce enough electricity during a cloudy day in winter to charge the battery enough to provide heat at night), and what happens if the panels are covered in snow.
I have explored many different option for batteries and generators. There is no perfect solution and all solutions are expensive. You can cover some scenarios for providing power during a grid outage, but there is no solution that covers all scenarios, particularly ones where you are away for long periods and we also have a grid outage that last more than a day or so. Remember that gas-powered back up generators regularly fail to start in cold weather (even if they have been regularly serviced, I speak from experience) and run out of gas.
I think the F150 with an automated transfer switch is the best option (for us) because it is relatively cheap (maybe $1,000 on top of the Ford) and can last 3 days even with thick snow. But this only works if your EV supports home charging. Today only the F150 really does (Nissan claims the Leaf can but I am skeptical), but most manufacturers (including Tesla) have announced that they will support vehicle-to-home (V2H in the lingo) in the future. If you see an EV in your future, which you mentioned you did, this is likely the best option. However, it could be a few years away and that means you need a back up plan for heat in arctic cold weather during a grid outage before you get the EV with V2H. The realistic options are a gas-powered generator (with enough output to run the heat pump) or a propane heater.