Covering all of your electrical needs with solar is an admirable objective, though not always the correct one. If you are financially constrained to a certain solar investment size, then spending that money most prudently is more important than supplying all of your electricity with solar.
If future property investments include replacing inefficient AC units or appliances with high-efficiency models, adding insulation, changing out old windows and doors, then better to downsize the solar system to match the lower electricity consumption projected after these improvements are made.
Unshaded, southeast to southwest facing roofs with solar panels will contribute to the most efficient power production. If the capability of panels maximizing this space is not enough to supply all of a property’s electrical needs, there are a few options.
It is very important at this point to understand the extra cost versus the annual estimated power produced with these other options, such as added panels on a ground mount, shade structure or less desirable roof exposure. Making electricity-reducing investments or supplementing solar with utility power may very well be the more economic options.
Where the utility does not buy back excess solar electricity production during the day at a high enough price for the property to repurchase economically at night, then the solar system only needs to be sized to meet daytime requirements. This is often only 20% of the total consumption.
Using the combination of solar and batteries to provide electricity off-grid would not mean sizing the system to that of an equivalent grid-tied property. The added expense of batteries would have you looking at ways to save on electricity consumption first. Can likely justify some very energy-efficient equipment over more panels or larger batteries.
Paying cash for solar should come with the expectation of earning an average annual return of 12% over the 25+ year system life. If projections do not meet these targets, then one possibility is that the system is too large and inefficient. The other is that you are paying too much for the system. Shop around.
Financing solar should yield monthly payments at least 20% lower than estimated utility cost savings. If this is not the case, then the financing terms could be poor, the solar system design inefficient or the price too high.
The correct answer does not need to be a purely financial one. There is a lot to be said about the pride it brings to supply 100% of one’s electricity needs from the sun. Security also enters into the equation by adding battery backup for complete independence from the utility and the possibility to live off-grid.
So, in many ways, the decision to size a solar system to cover all of your electrical requirements needs to consider the options for reducing electricity consumption in the future, utility buy-back programs, placement of panels at the properties, financial terms and capacity, optimal economics, pride and security.
Size can matter and bigger doesn’t mean better!