• Have you tried out dark mode?! Scroll to the bottom of any page to find a sun or moon icon to turn dark mode on or off!

diy solar

diy solar

Eliminate Propane when Adding Solar, or Keep Some Propane Appliances?

davemill

New Member
Joined
Jul 20, 2024
Messages
5
Location
Santa Cruz CA
Currently propane powers the furnace, tankless water heater, dryer and stove in our 1800 sf home in Santa Cruz, CA (no AC). All those appliances work fine, but we dislike the stove. We are planning to add solar, but don't know how to think about replacing the propane appliances with electric, since those would be among the largest power consumers. It seems like the economical choice might be to keep some of those propane appliances, at least in the short term.

Note: The NEM3 rate plan in CA pays so little for power sent to the grid that the few residential solar projects these days seem to include large battery capacity.

Thanks.
 
Welcome to the DIY Solar Forum @davemill
There are a lot of CA members here that will help you,
the whole going solar and maybe dropping the Propane is a tough question to answer - "it depends"
Some things going for your are good solar all year around - start by going to PVWatts.nrel.gov and plug in your location and 1kW PV - use your latatude for the PV angle due south and see what your area has to offer during Nov - January (typically the poorest solar months)
Then take your utility bill and see what your consuming now, before the propane shift, as a starting point.
Everyone here on the forum will help you.
Ok did the PV Watts for you for Santa Cruz, 1kW PV array due south tilted to 37 degrees:

January3.8995
February4.86106
March5.38128
April6.30143
May6.22145
June6.45145
July6.21142
August6.33144
September6.05134
October5.73135
November4.72109
December3.7090
Annual5.491,516
 
What PV Watts tells you is December is the poorest month, at 90kWh per 1kW of PV array, or about 3kWh per day per 1kW of panel array size.
This lets you scale up - say you determine you need 27kWh per day on average, and want to size the array for the worst month (Dec) 27/3 = 9 so you would want at least a 9kW array of PV.

If you are planning to use a roof for PV panels, you can use PV watts to estimate the solar you can expect to get from each roof area, by pluggin in the actual direction it points - ie if not due south, and the pitch of the roof rather than the 37-degrees we started with. Maybe you want to compare a ground mount at 37-degree tilt to a roof area at 18 degree pitch: PV watts let you plug in any combination of 'test' set ups you like and save the results. This can be handy. One caution for PV watts - shade from trees or other buildings etc will dramatically affect the solar potential.
 
You could keep them, then swap them one at a time so you know what your capacity is. Just over the next few years so you can see how the whole season goes with the next electric appliance.

I put up a small 2kW array for my phase 1, and the nice thing about that is that I have real world data for my location. I know what scaling up 7x (my phase 2) will do. No guesswork.

Good luck with your project. You will get where you want to be if you stick to it.
 
You could "guesstimate" the amount of BTUs you are using in your smaller propane appliances by running them off a BBQ tank for a while. Weigh the tank before using, attach the appliance to the tank/regulator, run it for a while (maybe a few weeks or month), then weigh the tank again. That will tell you how much propane that appliance used during that time period, and you can convert that to BTUs, and extrapolate to a full year. This should work for your stove/range, dryer, and maybe the tankless water heater (depending upon how many BTUs it needs). That will give you an estimate for how many BTUs and eventually electricity you will need to run those same function with electric appliances (with some conversion from BTU to watts). Probably won't work for your furnace, as it likely uses too much gas for a BBQ regulator to give it enough propane to run.

Or if you are just looking for an overall figure, you probably know (or can find out) what your yearly propane usage is in gallons. Again convert that to BTUs and then KWHs.

These will give you a ballpark number of how much more electricity you would be using to replace these appliances. What it won't tell you is what the crunch points will be in your system (cloudy winter spells, periods of high use, etc), and how the various efficiencies will change the numbers (but in general, electric appliances will be more efficient than gas).

Anyway it would be a start in getting some numbers.
 
Welcome to the forum from a fellow Santa Cruzan. We're in the San Lorenzo Valley.

Currently propane powers the furnace, tankless water heater, dryer and stove in our 1800 sf home in Santa Cruz, CA

We do have propane as well, but only for cooking. If you have a propane dryer, that may be a good candidate to replace with a heat pump electric dryer. I replaced our resistance (conventional) electric dryer and the difference is huge.

The heat pump dryer makes even sense if you don't have solar panels. E.g. we went from 4kWh for one dryer run to 0.8kWh.
That's most likely cheaper than running a propane dryer.

Propane has the benefit that you can store it for a very long time, and you can hook up a propane powered generator to it to charge your batteries in case of a power outage. You are probably familiar with the outages if your property has a propane tank instead of natural gas.

Do you plan to build the system yourself such as an off-grid system, possibly without permits, or do you plan to have it grid-tied and with permission of County and PG&E?
 
Disclaimer: my mindset is gas vs electric, not propane vs electric, since I get gas delivered by PG&E to my house.

So you need to think about this in terms of both energy and power.

The main intersection with NEM3, if you care to use NEM3 vs a non NEM interconnection plan, is that NEM3 sizing is based on how much electricity you use. Not sure how much they'll enforce for the small size of system under discussion here. Also, if you hire out the project you can probably get a better deal doing it in one chunk, instead of adding more later. Permits and interconnection have a fixed amount of red tape per project, so if you do it in one shot vs two, you save the headache.

furnace, tankless water heater, dryer and stove
I would say in terms of impact, go after the water heater first. Then pick between dryer and stove depending on the non-energy benefits they give you, as well as your habits. For instance, we don't run that much laundry through the dryer, and looking at my consumption data I easily use 2x more energy per month on the induction stove than the resistive dryer. But a family that generates a lot of laundry would easily reverse this. Switching from gas to induction gave me a nicer stove to work with, while switching to a better dryer ... maybe vaguely is more gentle on my clothes.

If you're thinking about EV, I would work that out first before the furnace, since you can easily offset non-winter EV use with a reasonable size solar setup.

Furnace would be a real challenge to offset with solar. It is one of the biggest energy and power users. And it needs the energy in the months without much solar. Furnace is the highest energy in the house, and either #1 or #2 if you charge EV at home. I think you can maybe offset the heating in shoulder season, which admittedly is pretty long in the Bay Area. Where I am, March through May, it's feasible to generate enough from rooftop solar to heat your house completely.

Tankless is a massive power user and the second most energy in the house. Tankless water heater can be swapped out for Heat pump water heater, and there are some quite decent local incentives. HPWH use a lot less power, over longer time, which helps with solar. Peninsula Clean Energy is offering $2000 for a swap away from gas (not sure if they cover propane). The main constraint here is whether you can fit one in. They are way bigger than a tankless. They also make more noise than a regular tanked water heater. But they should be much quieter than a running tankless heater.

Stove is high-ish power but does not use very much energy. My home office uses more energy per month than my kitchen. I cook a lot and I'm super happy with induction, though it may be a bit challenging to find an induction stove that responds the way you want. It is pretty easy to find one with way more power output than you can handle, and delivering this power without heating up the house. I actually have to bundle up in the kitchen sometimes.

Dryer is a massive power user. The HP dryer will make drying much easier to run off solar. Dryer often is well behind water heating in home energy use, of course it depends on how you use it. This segment of appliance is innovating quickly, so there are more options than ever. The improvements are mostly around things like form factor and ease of cleaning rather than efficiency.

Another advantage of HP dryer is that it will save you a bit on heating bill, since they are unvented and do not draw heat out of your house during operation.
 

Eliminate Propane?​

If you dislike getting propane delivered, or it's too expensive, then consider dumping it. If not, why not keep it?

There are some uses (lighting, refrigeration, motors) that electricity just works better for. But for heat, both propane and resistive electric are very similar in efficiency (close to 100%.) You can get higher effective efficiencies than that with a heat pump, but they are much more expensive. Specifically:

furnace - keep for now, if you really want to replace it, switch to a heat pump with propane backup
tankless water heater - keep
dryer - keep
stove - keep, if you really want to replace it for other reasons, consider an induction cooktop
 

diy solar

diy solar
Back
Top