# Solar Calculations

From Open Source Ecology

- 1kW pv system - 1400 kWhr
- 6 hr/day average - not! 3-4.5 kwhr/day [1]

- Fuel is about 35 kWhr/gal [2]. Let's say it's used for generating electricity - about 33% efficient - [3].
- To get electricity - 11 kWhr/gal equivalent. Gal is about 3 kg
- This gets us to 127 gallons of fuel displaced - 42 gal. Ie - each kW installed gets rid of 3 barrels of oil!
- Let's do PV roof on SEH - 7 kw - 21 barrels of oil displaced!
- At low limit, we have 3 kWhr/kW installed per day - or 21 kWhr available per day.
- Average Electricity Cost implies $2.73 available per day. That is almost exactly $1k saved per year at the low limit. Makes sense. But we are also efficient on heat pump - for cooling and heating - saving heating bills in winter. And we cook on electric and heat water electric - saving on the gas costs. So displaced costs are