It doesn't worth it at all.
Photovoltaic panels are VERY expensive (over 5 $ per watt) and have fairly low energetic efficiency. And if it was not enough, all heating apparatus require a lot of power. Soto build a small 500 watt heater, you would require a 2000-2500 $ panel array. In fact, photovoltaic panels are used in conjunction with high efficiency battery chargers and high efficiency DC-DC or DC-AC converters to power energy efficient devices which DO NOT include heaters !
Reflective solar heaters on theur side, are far more energy efficient and can be built from inexpensive materials.