Should save you quite a bit on gas over the years. 

I have 2 stacked units in a 2 family student rental ( 8 beds ) on one hand i wish i did not get them because i have been having to reset the machines ( have to have someone look at that) so in that sense i wish i didn't have them because of this maintenance, but if the Students lived in a dorm they would have to pay to do laundry and the local laundry mats are twice what i charge, it's more for convenience for them. the money i do get helps pay for the gas, water and the electric that the machines use as @Dale Stevens mentioned. i do not make money on them, but helps with the cost when the rental market is so competitive for student housing where this is.

Did they stress out over not having enough by spending an extra few minutes to depower the entire home before leaving or drive an extra ten minutes to save $0.08 per gallon of gas?

Roof still have 10-15 years left, new gas furnace, new ac unit central air.

It currently has heat only( original 50s gas furnace).

And if you do bang on 5,000 doors you're probably going to spend a chunk of money in gas.  

One-time Expenses$1000 - Acquisition Costs (minor rehab, legal, & inspection)Annualized Expenses10% Gross Annual Rent - Vacancy Costs (turnover & lost rent)10% Gross Annual Rent - Property Mgmt (standard)$1176 - Repairs & CapEx ($1 per sq foot for tpical property)$1516.46 - Property Taxes (5 year historical average for typical property + 10%)$1000 - Property Insurance (a nice round number: seller reported that he paid $708/mo for one duplex)$27 - Water & Sewer (average across several properties from last month)$0 - Gas, Electric, HOA, Snow Removal (tenant pays or not applicable)$60 - Lawn Care (I made this number up)COMPARATIVE ANALYSIS:This is my analysis of the five properties that are being negotiated right now, listed from best to worst.Property Alpha (two-flat)$1250 - Income, Monthly (actual)$567.37 - Expenses, Monthly (estimated)$42,000 - Price, Signed Contract36% - Cap Rate (Annualized Income / Price)16.6% - ROI, After Tax (annually, assuming 15% income tax)6.0 Yrs - Until this property pays itself offProperty Bravo (two-flat)$1100 - Income, Monthly (actual)$537.37 - Expenses, Monthly (estimated)$42,500 - Price, Signed Contract31% - Cap Rate (Annualized Income / Price)13.1% - ROI, After Tax (annually, assuming 15% income tax)7.6 Yrs - Until this property pays itself offProperty Charlie (duplex)$1075 - Income, Monthly (actual)$532.37 - Expenses, Monthly (estimated)$55,000 - Price, Informal Discussion23% - Cap Rate (Annualized Income / Price)10.7% - ROI, After Tax (annually, assuming 15% income tax)10.3 Yrs - Until this property pays itself offProperty Delta (SFR)$875 - Income, Monthly (actual)$492.37 - Expenses, Monthly (estimated)$48,000 - Price, Informal Discussion22% - Cap Rate (Annualized Income / Price)8.8% - ROI, After Tax (annually, assuming 15% income tax)13.6 Yrs - Until this property pays itself offProperty Echo (SFR)$770 - Income, Monthly (actual)$471.37 - Expenses, Monthly (estimated)$62,500 - Price, Informal Discussion15% - Cap Rate (Annualized Income / Price)4.1% - ROI, After Tax (annually, assuming 15% income tax)24.4 Yrs - Until this property pays itself offNotice how the price keeps going up?

What are you TOTAL monthly expenses including gas, food, gifts, movies, mortgage, dinners out etc?

The energy source for hot water heating can be either gas or electric.

Its found at many gas stations like 711 and other places, I barely know about it.