I just got my “True Up” bill from PG&E—it has been about a year since the solar panels were installed. During that time, the panels generated about 2.63MWh of electricity (7.2kWh/day): 77kWh more than we used during the year. PG&E reimbursed me $2.11 for the extra electricity, but wiped out the $106 of Net Energy Metering credits that we had accrued from generating electricity during peak time and using electricity during off-peak times.
Next year, we’ll be facing a minimum delivery charge of about $120 for the year. If we follow the same peak/off-peak usage, that means that we could use about another $226 worth of electricity without increasing our bill (other than losing the $2.11 credit). That would be about 1.5MWh off-peak, or only 660kWh peak consumption. What that translates to for us is that I will be buying a dehumidifier for our house, to reduce the condensation on the walls. Current Energy Start rated dehumidifiers remove about 1.85 liters of water per kWh used, and I don’t think we need to remove 2775 liters of water a year (7.6 l/day) from our house, so the dehumidfier will add nothing to our electricity bill. Based on reviews (in Consumer Reports and on Amazon), we’re looking at the 30-pint Whynter RPD-321EW Energy Star Portable Dehumidifier, is it has good performance in cool rooms (our house gets quite cool in winter, especially when we’re both at work) and is relatively easy to empty (we don’t have a convenient way to rig up a drain hose).
We are fairly light users of electricity by US standards. We used about 2.63MWh a year, but the US average is 10.932 MWh/year, and the California average is 6.744MWh/year [https://www.eia.gov/tools/faqs/faq.cfm?id=97&t=3]. PG&E also reports what people in our area use: similar houses use 6.042MWh/year, and efficient similar houses use 3.262MWh/year [https://pge.opower.com/ei/app/myEnergyUse].
Part of the reason we use so little electricity is that we rely on natural gas for heating, hot water, cooking, and clothes drying, using about 433 therms a year. Here we are not particularly efficient: PG&E reports that similar houses use 548 therms/year, but efficient similar houses use only 293 therms/year [https://pge.opower.com/ei/app/myEnergyUse]. Shorter showers and setting up a clothes line would probably reduce our usage, but heating is the biggest chunk, and our house is already as cool as we are willing to live in. We’ve invested in insulation over the years, but there is only so much you can do with a poured-concrete house for sane amounts of money.
A therm is about 29.3001 kWh, so our natural gas use is about equivalent to 12.7MWh—much more energy usage than our electricity!
We’ve been planning to buy carbon offset credits for our energy usage this year (see previous estimates in Solar lies). Nothing for electricity of course, since we had a slight surplus there. According to PG&E, natural gas produces about 6.1 kg CO2 per therm (and their electricity generation is about 238 g/kWh, only slightly more than the 208g for the same amount of energy from natural gas) [http://www.pge.com/includes/docs/pdfs/about/environment/calculator/assumptions.pdf].
I calculate approximately the following CO2 production from our various uses this year:
- 2.64 MT (metric tonnes) for natural gas
- 3.37 MT for plane flight to Illinois (2 roundtrip tickets) [https://carbonfund.org/individuals/]
- 6.97 MT for plane flight to Montreal (3 roundtrip) [https://carbonfund.org/individuals/]
- 0.5 MT Other transportation (bus and train)
- 13.5MT Total
My wife and I have considered taking another trip this year, to Boston, which would add another 4.9MT. Note that flying is by far the most energy intensive thing we do—reducing travel is probably the only way we could significantly reduce our carbon footprint. As carbon offsets, we’re considering projects like https://www.cooleffect.org/content/project/efficient-cookstove-project/, which cost $6–$10 per MT. Do any of my readers know of good carbon offsets that aren’t scams or just enabling polluters?