28 May : I met someone today who got a quote for his house... but the supplier would not quote as the roof faces East. Actually, the orientation is the same as for my house, its ridge is north south, but tilted 10 degrees to give favour for the sloping pitch to the East.
My observation after nearly a year of this is that MORNINGs are less cloudy statistically , and more to the point, the air temperature is lower in the morning after the night. PV efficiency is closely linked to temperature. Cool panels produce more in similar sun angles etc. and East seems to work acceptably. Afternoons seem to be marred by broken cloud blowing in, even when the morning started by looking very clear skied.
The Peveril solar house will meet all its annual energy costs from this east roof, plus a healthy surplus, despite the East angle.
The other question is Low sun angles from trees. Well the harvest in Dec and Jan is so small that the very low angle is not worth worrying about (also deciduous trees are not usually in leaf in winter). Two good days in May/June can be equivalent to the whole month of December or January, and the chances of these coming are random, but good. If you have a good April or May, the difference between that and the expectation can be more than the entire harvest in December.
You must be careful not to have anything shading the active surface during the summer months, such as a tall chimney or tree that will grow higher and more foliated in summer.
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