Regarding the solar -- Have never been able to pencil this out. Will you be DYIing the solar project. Kinda hoping you are. You would probably save 50% on the cost and you could write a great piece for us to model.
Just curious about your comment on saving 50% with DIY. I was looking for 12 250W panels. At that scale DIY wasn't that close to the installer cost once I included everything. My best quote came back at $2.74/Watt (after federal incentives) of installed panels, a grid tie inverter, the installation and a 25 year warranty on the panels and workmanship. For DIY I could find panels for $1.00/watt (after shipping), Inverter for ~$0.40/watt, permits and electrician to do the panel work added $0.16/Watt, Mounting hardware and roof flashing $0.20/watt, Cables and conduit $0.05/watt. So we are at $1.81/watt and I just have a pile in my back yard. So possible to save money. Unfortunately in my area DIY systems are ineligible for production based incentives from the power company. Mine will be $0.03 per kwh or about $120/year. If I value that like an annuity at 5% we're talking another $2400 or $0.80/watt.
If I were going to do a DIY system I would first work on getting as much of my house running on 12 V as possible (lighting, computers, screens, routers, maybe fridge etc.) then I would do an off grid 12V solar system for those things. Bakari has a really good how-to on instructables: http://www.instructables.com/id/NON-grid-intertie-independant-solar-photovoltic-/
Love the 12 volt concept! Fits right in with reduce, reduce, reduce.
The $2.74 per watt --- does that include any kind of batter system. One problem with solar panels is that a majority of my power usage is at night. So without batteries it isn't of much use to me. When I looked in the past, batteries would basically double the cost of a system.
I'm sure the outcome varies by where one lives in the country and what electric rates are. A 65 watt light bulb cost me about $7.50 a year to run here. (3 hours per night, every night) If I had to spend $178 dollars on a panel for that light, (2.74 times 65) that panel would need to generate about $20 of electricity to come close to penciling out. My guess is that the panels are only actually delivering power about 65-75% of the time. In other words my 65 watt light is on demand while the cost for solar panels is ongoing regardless if they are being used or not.
I have seen the deals in sunny south California that seem to make somewhat of sense penciling out, but definitely not at my local.
That is why I think the method for the OP might be better served to seek other manners of reduction such as the freezer to fridge conversion.
It does not include any type of battery system, I just tie in with the power grid, but in Colorado, we get "net-metering." So each month, they take the amount of electricity my house uses, subtract the amount the panels generated and charge me for that number of kwh. This solves the "majority of power usage is at night" issue. If I generated more than I used in one month (like in the summer when there is lots of sunlight during the day and shorter nights when you need light), then that power is banked as a credit I can use to offset my usage in the winter 1 for 1 (if I generate 1kwh more than my usage in July, I can subtract one kwh from my bill in December in addition to the kwh I generate in December).
As for your math, you are entirely right that a dollar spent reducing demand is almost always a better idea than a dollar spent on solar panels.
You can actually figure out how much energy a panel will generate in your area based on location, weather, panel position, etc using:
http://pvwatts.nrel.gov/According to their math, my system should generate about 3900 kwh/year or about $511 off my bill annually. So I pay about $8200 and get $511/year which equals a return of 6.2% which will increase every time that power rates go up. I'm happy with that rate of return especially b/c utility rates are expected to go way up in the near term in our area. At the same time though, I got a better return buying LED bulbs to replace my incandescents (15%), halogens (8%) and got LED backlit computer screens (20%) and a way better return when I bought our high efficiency washing machine (43%) and plastic wrap for some windows in winter (125%).
So do the math but that reduce, reduce, reduce is a very good mantra :-)
