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Thank you so much for reaching out with this excellent question.

So these are two separate credits, I'll address them each individually. 

Electric Vehicles:

A tax credit is available for the purchase of a new qualified PEV that draws propulsion using a traction battery that has at least five kilowatt-hours (kWh) of capacity, uses an external source of energy to recharge the battery, has a gross vehicle weight rating of up to 14,000 pounds, and meets specified emission standards. The minimum credit amount is $2,500, and the credit may be up to $7,500, based on each vehicle's traction battery capacity and the gross vehicle weight rating. The credit will begin to be phased out for each manufacturer in the second quarter following the calendar quarter in which a minimum of 200,000 qualified PEVs have been sold by that manufacturer for use in the United States. This tax credit applies to vehicles acquired after December 31, 2009.

So depending on the manufacturer of your vehicle and how many they've sold in the US you will get between $2,500 and $7,500 credited to you.

This is a refundable tax credit and any amount that reduces your tax liability beyond $0 is refundable.

Here is a list of how much the credit is worth by manufacturer:
https://www.irs.gov/businesses/irc-30d-new-qualified-plug-in-electric-drive-motor-vehicle-credit

Source: http://www.irs.gov/Businesses/Plug-In-Electric-Vehicle-Credit-IRC-30-and-IRC-30D

As far as the Solar System:

The federal residential solar energy credit is a tax credit that can be claimed on federal income taxes for a percentage of the cost of a solar photovoltaic (PV) system. (Other types of renewable energy are also eligible for similar credits but are beyond the scope of this guidance.)

The system must be placed in service during the tax year and generate electricity for a home located in the United States. There is no bright-line test from the IRS on what constitutes “placed in service,” but the IRS has equated it with completed installation.

In December 2020, Congress passed an extension of the ITC, which provides a 26% tax credit for systems installed in 2020-2022, and 22% for systems installed in 2023. (Systems installed before December 31, 2019 were eligible for a 30% tax credit.) The tax credit expires starting in 2024 unless Congress renews it.

There is no maximum amount that can be claimed.

The following expenses are included:

• Solar PV panels or PV cells used to power an attic fan (but not the fan itself)
• Contractor labor costs for onsite preparation, assembly, or original installation, including permitting fees, inspection costs, and developer fees
• Balance-of-system equipment, including wiring, inverters, and mounting equipment
• Energy storage devices that are charged exclusively by the associated solar PV panels, even if the storage is placed in service in a subsequent tax year to when the solar energy system is installed (however, the energy storage devices are still subject to the installation date requirements)
• Sales taxes on eligible expenses
  

This is not a refundable credit so it cannot reduce your tax liability below zero, however any unused amount can be carried back one year and carried forward 20 years per Section 48 of the Internal Revenue Code.

Source: https://www.energy.gov/eere/solar/homeowners-guide-federal-tax-credit-solar-photovoltaics

I hope this helps make your tax life a bit easier, thanks for the great question!

-Dennis