Keep insulin and other cold-chain medicines cold on solar power
Some medicines (for example insulin, some biologics and vaccines) need refrigeration. On an off-grid estate the medicine fridge is a critical load that must survive cloudy days and power faults.
How
- Check the label or ask the pharmacist for each medicine's range. FDA gives unopened insulin storage at about 36 to 46 F (about 2 to 8 C). In-use vials or cartridges can be kept at 59 to 86 F (15 to 30 C) for up to 28 days. Some products differ, so check your label. Never use insulin that has frozen.
- Use a dedicated medicine fridge, not the family food fridge. CDC advises against dorm-style or bar-style combination units for vaccines because they can freeze contents.
- Monitor with a digital data logger or min/max thermometer with a buffered probe, placed in the centre of the fridge, and check it at least twice a day. Keep medicines off the door shelves and away from the walls.
- Bottles of water on the shelves and floor of a household-type fridge help stabilise temperature (CDC).
- For long outages, look at solar direct drive (SDD) medical refrigerators prequalified by WHO (category E003). They store cold in a thermal mass instead of a battery. One example datasheet (Dulas VC150SDD) lists about 3.2 days of autonomy at +43 C and an array over 600 Wp.
- Use the cold-storage calculator to give the power designer a daily kWh figure, and put the fridge on a protected circuit (see thermal-25 and power-1).
- Keep a cooler and chemical ice packs ready as Ready.gov suggests, without letting medicines touch ice and freeze.
- If the power is out for a day or more, replace refrigerated medicines unless the label says otherwise. Call your doctor or pharmacist, and use the warmed medicine only until a new supply arrives (Ready.gov).
Safety: If insulin or another lifesaving medicine is exposed to heat or loses refrigeration and no replacement is available, FDA says it may be used until a new supply is obtained. Contact a clinician as soon as you can.
Do these first
Sources
- Information Regarding Insulin Storage and Switching Between Products in an Emergency. US Food and Drug Administration (FDA), accessed 2026-11
- Pink Book Chapter 5: Vaccine Storage and Handling. CDC, accessed 2026-11
- PQS category E003: Refrigerators and freezers. World Health Organization (WHO) Prequalification, accessed 2026-11
- VC150SDD solar direct drive refrigerator datasheet (2025). Dulas Ltd (manufacturer), accessed 2026-11
- Tips for Medications. Ready.gov (US FEMA), accessed 2026-11
- Safe Drug Use After a Natural Disaster. FDA, accessed 2026-11
- Estimating Appliance and Home Electronic Energy Use. US Department of Energy, Energy Saver, accessed 2026-11
- Power outage safety tips (Ready.gov leaflet, hosted by Cal Poly Pomona). Ready.gov / FEMA, accessed 2026-11