Why aren’t solar panels on every sun-facing home? Most will say the exorbitant installation costs.

While residential solar has made strides, Groupon (GRPN) and Elon Musk’s SolarCity (SCTY) are hoping to give it an extra jolt.

The two announced a partnership on Wednesday to offer a “daily deal” -- paying a dollar for $400 off of home solar power. This is SolarCity’s first national deal and comes amid rising competition to dominate residential solar power.

With the purchase, buyers will get a free consultation from SolarCity, and the $400 discount will be applied to the site survey and installation. This really only appeals to people willing to chalk up the remaining tens of thousands of dollars to install a three- or four-kilowatt PV system. 

The cost of a PV system varies drastically depending on the system size, shape of house, access to sun and location.

According to Go Solar California, the total average cost of an installed residential PV system under the California Solar Initiative was $8.70 per Watt including installation as of January 2011. That translates to about $34,800 for a four-kilowatt system, the average size of a residential installation. However, proponents of solar say it will save money over the long term by essentially taking the home off the energy-devouring power grid. 

Despite the solar push, shares of both companies traded in the red on Wednesday, with those of Groupon down 2.3% to $6.13 just ahead of the market close, and SolarCity’s slumping 1.77% to $52.25.

The deal, only available in 15 U.S. states, will be offered over the next four days.  

Follow Jennifer Booton on Twitter at @Jbooton