Which would be the best option for cost and environmental benefits?

Would installation of a fast-charging plug at home to use for off-hours charging or solar installation with battery storage to support EV charging be the best option?

It depends on your home and driving needs. Many people who travel less than 50 miles a day or have a plug-in hybrid are happy with L1 overnight charging from a regular 120v  outlet, and you may already have one in your garage or driveway. Adding a Level 2, 240v charger can cost as little as $800 or so if you have an uncomplicated install, but can get more expensive if you need to upgrade your panel. Solar with storage can cost more than $15,000 and on up, but will pay off in lowered electricity costs over the years, so it really depends on your driving needs and budget.

The federal Inflation Reduction Act can help with reducing the cost of panel upgrades, adding solar, and storage. 3CE can help with the cost of a panel upgrade or adding a charger, if you are in their service territory. SB Home Power is a new program to  help you add solar and storage, and also contact a couple local solar installers to compare quotes.