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Has anyone looked at household power consumption before and after children move out?

calum_wilde | Posted in General Questions on

I’m curious about solar pv sizing and how to make estimated predictions for power consumption once my kids have moved out. Or if they make an appreciable difference in this context.

I don’t think it’ll matter for this question, but I’m in climate zones 6a

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  1. GBA Editor
    Martin Holladay | | #1

    Make a spreadsheet and do the math. The departure of children won't change HVAC energy.

    The significant changes are : (1) domestic hot water, and (2) plug loads.

    If you know (or can estimate) your domestic hot water for 4 people (say) -- two adults and two teenagers -- the kitchen use will drop by 1/4 or 1/3 when the kids leave, and the showers will drop by 1/2. Make some estimates and assumptions.

    For plug loads, go to their bedrooms and count the number of computers and gadgets. Add it up and put the numbers on the spreadsheet.

  2. calum_wilde | | #2

    Thanks Martin.

  3. brp_nh | | #3

    If you're thinking about adding solar PV and you live in a state with good net metering policies that allow you to accrue credit on your account and you could see yourself with an electric car in the future...I'd suggest maximizing the size of your system.

    We put solar PV on our new house in 2015 before we knew our full year electric use. We decided to max out the south facing roof and built up over 4 MWh in credit over two years. So, we oversized the system for the house, but that credit is now great for our Nissan Leaf.

    Long story short: think about an electric car when sizing your system.

  4. Expert Member
    Dana Dorsett | | #4

    There is a lot of anecdotal evidence of large drops in electricity consumption (and even HVAC energy use) when children move out, but you should be able to predict it. If your kids are prone to leaving the game computer & montior on, taking endless showers, leaving lights and fans on, bumping the AC thermostat down to 65F in summer and heating T-stat up to 75F in winter the differences can be large.

    Those who love empirical evidence for making those projections can always buy some of these:

    An eventual electric vehicle (EV) load will probably sop up any excess, assuming you are driving fossil-burners rather than EVs now.

  5. calum_wilde | | #5


    We presently don't have any south facing roof but the plan is to build a garage regardless so I'm hoping to use that roof for the solar PV project down the road. In keeping with that I plan to make sure the garage is orientated and the roof is sized and shaped to get the most out of PV system. So, at this point, I'm trying to figure out how much south facing roof I'm going to need in an effort to figure out how I want the roof trusses shaped. Possibly a little backwards from the norm, but hopefully we'll get there in the end. Luckily we do have good net metering policies here.



    Thanks. That's the kind of thing I was expecting, lot's of likely accurate but at the same time anecdotal information. Still, you make lots of great points about the habits of those not paying the bill. :)

    I'll take a look at that link.

    Thank you.

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