So there's no real way to determine what the value of the panels would be and what you can charge extra for them because everyone's electric bill depends upon their usage.  

;) You will find that with real estate investing across the US, agents aren't completely necessary (yes, they can be helpful) you simply need a wholesaler.

I think not, because they may not be careful of their usage.

I feel like its an inappropriate thing to ask.

If you operate your plumbing business from the property, then some % would be allocated to business usage.

Is this inappropriate? 

When the lender bases the refi on the income approach (since that's its current usage) the paper equity you thought you had is gone because they originally lent you money based on the sales comparison approach not the income approach. 

Your jurisdiction will likely charge each meter a new connection fee even though you are not causing a net increase in usage.

This will help you keep your water in check.Or, do sub-metering where the tenants pay for the water usage.

It reduces the temptation to juggle money inappropriately as your construction costs inevitably change.