In addition to the above response, the instructions state:
"Section B—Residential Energy Property
Expenditures
Residential energy property costs are costs of new qualified energy
property that is installed on or in connection with a home that you
used during 2023 located in the United States. Include any labor
costs properly allocable to the onsite preparation, assembly, or
original installation of the energy property. Qualified energy property
is any of the following.
• Certain electric or natural gas heat pump water heaters; electric
or natural gas heat pumps; central air conditioners; and natural gas,
propane, or oil water heaters.
• Natural gas, propane, or oil furnaces and hot water boilers.
• Certain biomass stoves and biomass boilers.
• Certain improvements or replacements of panelboards,
subpanelboards, branch circuits, or feeders.
To qualify for the credit, qualified energy property must meet
certain energy efficiency requirements. See Line 22a
through Line 25a and Lines 29a Through 29e, later, for
details."
Nowhere in lines 22a to 25a nor in lines 29a to 29e does it state that it must be your main home.
