Secret to me, until now: Time of Use Rates
The adventures of installing rooftop solar panels on an existing home
There is much to learn! Like Time of Use rates.
Since I posted “Part One” I have had my roof inspected by the solar provider. One cracked tile was found, which they will replace, and they report “the felt is good.” They took photos of all aspects of the roof. I suppose I should get a copy of those. [Advice: ask for anything special as soon as possible, preferably before signing the contract. I requested photos after the fact and was ignored.]
They say they will be providing a 25-year warranty on my roof. That protects against leaks from the points at which they attach their panels to my roof.
Meanwhile I’ve been refining the numbers on my spreadsheet. Savings each month will vary according to how much solar is used and how much is taken from the grid. It is not simply the total generated minus the total used, because I only get a credit of 75% retail from the utility. So the more I use solar instead of the grid, the less I pay. I can calculate a maximum savings (all solar used, none sent to the grid) and a minimum (no solar used, all sent to the grid). For projections, I’ll use a figure midway between those two points.
Solar is not a substitute for conservation.
Solar panels on your roof does not mean you should use electricity with abandon. In fact, you should be conserving energy whether or not your go solar. You may find you save so much money by conserving that adding solar panels is unnecessary or not cost-effective. You need to compare the cost of solar versus your energy use AFTER employing conservation measures, not before.
Change all your non-LED light bulbs.
LEDs use about 1/10 the amount of electricity as old-fashioned incandescent bulbs. They last much longer, and the payback on replacing old bulbs is only a year or two. Your local utility may even provide some new light bulbs for free.
Turn off outdoor lighting during the day.
You can use LED light bulbs that turn themselves on when it’s dark. Be sure to get the dark yellow ones that don’t screw up the insects and birds. Ordinary LED bulbs may be screwed into sockets that are only on in the dark. Your local utility may provide some of these for free or at a substanial discount.
Use smart sockets.
Many appliances use electricity even when they are off. Shut them down as much as you can. For instance, kitchen appliances may be plugged into smart sockets that automatically turn themselves off overnight.
Seal doors and windows.
Plug up the cracks that allow cooled or heated air to escape.
Replace old appliances.
Refrigerators, dryers, hot water heaters and air conditioners that are over 10 years old are probably wasting energy. Your local utility may provide replacements for free or a substanial discount.
Install a “smart” thermostat.
Something like the “Nest” can reduce your electic usage by identifying times when you can be cooler or warmer. You can set it up to “pre-cool” your house on hot summer days, so you use less energy during peak times. Your local utility may provide a smart thermostat for free or a substanial discount.
Time of Use Rates
My research led me to something called “Time of Use Rates“. This is a plan that might provide savings to almost anyone, but especially for those with solar panels and a bit of discipline. Or it might be a total loser for those who’d rather not think about how they use energy. I’m going to give it a try, and I’m told I can cancel after 12 months and get a refund for any overage. All I had to do was notify NV Energy that I’d like to try those rates.
Basically they charge more (3.5 times as much, about $0.43/kWh!) for energy from the grid 1pm-7pm during summer weekdays. At all other times (evenings, weekends, wintertime) I pay about half the standard rate, $0.06/kWh. Sounds like if I’m willing to sweat a little during the summer afternoons, I can cool things off at night while saving money, perhaps 25-30% of my bill.
I don’t know if or how this affects the credit I get for kWh sent back to the grid. Most likely my credit fluctuates with time of use. Either way I’m bound to be using solar during those summer daylight hours and unlikely to ever pay the pumped-up peak price. As I learn more I’ll update this post.
Shift your usage!
In summer, when TOU rates from 1pm-7pm are outrageous, avoid using appliances and air conditioning. Dinnertime should be 7:30 or later to avoid using cooking appliances during peak. No dishwasher, washer, dryer etc. I pre-cool the house down to 75° from 11:45am to 1pm during summer weeks, then turn the thermostat up to 81° until 7pm. Today it was 106°. From 1pm to 4pm the inside temperature drifted up from 75 to 81 and the aircon kicked back on. It didn’t take much to keep it below 81 from 4 to 7.
In wintertime, when TOU rates are low all day long, shift appliance usage to the time when your solar panels are producing the most, 10am-3pm.
At this time it looks like TOU rates might cut $30-60 off my monthly bill, but will be even more beneficial once I switch on the solar.
My solar rep never mentioned “Time of Use”, probably because it might reduce my existing electric bills, thus reducing the cost-effectiveness of installing solar panels. When I asked him about it, he replied, “I think that is a great idea for everyone who has a solar system on their roof.”
In California, solar users who employ “net metering” to sell power to the grid must also adhere to “Time of Use” rates. There’s an article at Energy Sage but I can’t vouch for its accuracy, nor the comments.
Compare solar to what your electric bill should be, not what it is.
If you reduce your electric usage through conservation, you will need a smaller, less expensive solar panel setup. This affects costs and payback.
Don’t skimp on capacity.
Your objective is to produce as much electricity each year as you use. If your system produces too much, you’ve paid for capacity that has a relatively poor payback. Too little and you wind up shoveling too much cash back to the utility. Given the basic costs of designing and installing the system, don’t skimp on capacity.
Some solar contractors may low-ball your system capacity in order to provide an attractive price, but this is detrimental to your long-term payback.
Rough Draft of my spreadsheet. Click “Assumptions” tab after opening.