Possibly, but you should wait until 2023.
Firstly, "tankless" by itself is not enough to qualify. The appliance must "meet or exceed the highest efficiency tier (not including any advanced tier) established by the Consortium for Energy Efficiency which is in effect as of the beginning of the calendar year in which the property is placed in service." So it's not tankless that counts, but its overall efficiency. You will need to check with the manufacturer.
Second, the credit is claimed when the property is installed, not when it is ordered and paid for. If it is installed in 2022, the credit is 10% of the cost, including installation, up to a maximum of $300. There is also a $500 lifetime cap on all improvements under this section (doors, windows, furnace, etc) so you may have already maxed out the credit.
The law was changed starting January, 2023. If you install the property on or after 1/1/23, the credit is 30% of the cost, up to a maximum of $600, and the lifetime cap for energy efficient improvements is removed.
https://ttlc.intuit.com/community/tax-law-changes/discussion/faq-revisions-to-section-25c-energy-eff...
